How many centimeters are in an inch?

There are exactly 2.54 centimeters in one inch. To convert inches to centimeters, multiply the number of inches by 2.54. For example, 10 inches = 25.4 cm. To convert cm to inches, divide by 2.54 — so 30 cm ≈ 11.81 inches. UntangleTools performs this conversion instantly in the Length converter.

How do I convert kilograms to pounds (kg to lbs)?

To convert kilograms to pounds, multiply by 2.20462. For example, 70 kg × 2.20462 ≈ 154.32 lbs. To convert pounds to kilograms, multiply by 0.453592 — so 150 lbs × 0.453592 ≈ 68.04 kg. Use the Weight (Mass) converter on UntangleTools for instant results across mg, g, kg, oz, lb, stone, and metric ton.

What is the difference between the metric system and the imperial system?

The metric system (SI) uses base units of meter, kilogram, and liter, with decimal prefixes (milli-, centi-, kilo-) making conversions simple powers of 10. The imperial system uses feet, pounds, and gallons with irregular conversion ratios (12 inches to a foot, 16 ounces to a pound). Most of the world uses metric; the United States primarily uses imperial for everyday measurements. UntangleTools converts between both systems across all 13 measurement categories.

How do I convert joules to calories?

1 joule = 0.239006 calories (thermochemical). To convert joules to calories, multiply by 0.239006. For example, 500 J ≈ 119.5 cal. Note that 1 food Calorie (kcal) = 4,184 joules. The UntangleTools Energy converter handles joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, BTU, electronvolts, and more.

How do I convert watts to horsepower?

1 horsepower (mechanical) = 745.7 watts. To convert watts to horsepower, divide by 745.7. For example, 10,000 W ÷ 745.7 ≈ 13.41 hp. To convert horsepower to watts, multiply by 745.7. The UntangleTools Power converter supports watts, kilowatts, megawatts, mechanical horsepower, metric horsepower, and BTU/hour.

How do I convert degrees to radians?

To convert degrees to radians, multiply by π/180 (approximately 0.017453). For example, 180° = π radians ≈ 3.14159 rad, and 90° = π/2 ≈ 1.5708 rad. To convert radians to degrees, multiply by 180/π (approximately 57.2958). The UntangleTools Angle converter supports degrees, radians, gradians, arcminutes, and arcseconds — useful for trigonometry, navigation, and engineering.

How do I convert gigabytes to megabytes (GB to MB)?

In the decimal system (SI), 1 GB = 1,000 MB. In the binary system, 1 GiB (gibibyte) = 1,024 MiB (mebibytes). Hard drive manufacturers typically use decimal; operating systems often use binary, which is why a 500 GB drive shows as ~465 GiB on your computer. The UntangleTools Digital Storage converter handles bits, bytes, KB, MB, GB, TB, and PB in both binary (1024-based) and decimal (1000-based) systems.

How do I convert meters to feet?

1 meter = 3.28084 feet. To convert meters to feet, multiply by 3.28084. For example, 10 meters = 32.81 feet. To convert feet to meters, multiply by 0.3048. The UntangleTools Length converter supports millimeters, centimeters, meters, kilometers, inches, feet, yards, miles, and nautical miles.

How accurate is the UntangleTools unit converter?

UntangleTools uses NIST-standard conversion factors for all unit calculations, ensuring full scientific precision. All conversions are computed in real time directly in your browser, with no rounding until the final display step. The tool supports scientific notation for very large and very small values. No data is sent to a server — calculations are local and private.

UntangleTools

Free Online Unit Converter - Fast & Accurate

Our all-in-one measurement converter supports metric and imperial systems, delivering quick, reliable results for everyday and professional use.

Unit Converter

Instant · Precise · Universal

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"1" Meter

Every target unit at a glance

Source

Meter (m)

Tip: Click any answer value to copy it.

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31 conversions shown

How to Convert Meter to Centimeter

To convert meters to feet: multiply by 3.28084. To convert meters to inches: multiply by 39.3701.

1 m = 100 cm = 1,000 mm = 0.001 km. It is the base unit, so all other metric length units are derived by powers of 10.

For example, 1 Meter (m) = 100 Centimeter (cm).

Meter to Centimeter — Common Values

Quick reference conversion table showing common Meter to Centimeter values for length measurement
Meter (m)	Centimeter (cm)
0.001	0.1
0.01	1
0.1	10
0.5	50
1	100
2	200
5	500
10	1000
15	1500
25	2500
50	5000
75	7500
100	10000
250	25000
500	50000
750	75000
1000	100000

About Meter (m)

Definition

The meter is the base unit of length in the International System of Units (SI), defined as the distance light travels in a vacuum in 1/299,792,458 of a second.

Mathematical Relationship

1 m = 100 cm = 1,000 mm = 0.001 km. It is the base unit, so all other metric length units are derived by powers of 10.

Conversion Formula

To convert meters to feet: multiply by 3.28084. To convert meters to inches: multiply by 39.3701.

Practical Applications

Used for measuring room dimensions, building heights, athletic track distances, fabric lengths, and everyday object sizes.

Interesting Facts

The speed of light is exactly 299,792,458 m/s by definition — the meter is actually defined from this constant, not the other way around.

Common Mistakes

Confusing meters with yards — a meter is about 10% longer than a yard. Also, mixing up 'm' (meter) with 'mi' (mile).

Educational Tips

Remember: a doorway is roughly 2 meters tall, and an adult's stride is about 0.7–0.8 meters. Use these as mental benchmarks.

About Centimeter (cm)

Definition

The centimeter is a unit of length equal to one hundredth of a meter (10⁻² m), or 10 millimeters.

Mathematical Relationship

1 cm = 0.01 m = 10 mm = 0.3937 inches. There are 2.54 cm in one inch.

Conversion Formula

To convert cm to inches: divide by 2.54. To convert inches to cm: multiply by 2.54.

Practical Applications

Measuring height, waist circumference, screen sizes, furniture dimensions, and map scales.

Interesting Facts

The CGS system was the primary scientific system for over a century. 1 cm is roughly the width of an adult fingernail.

Common Mistakes

Confusing cm and inches — a common error in international contexts. Always verify which system a measurement uses.

Educational Tips

Your fingernail width is roughly 1 cm — a handy mental reference that's always available.

Unit converter guide

Free Online Unit Converter: 13 Categories, Every Result at Once

Convert length, mass, temperature, volume, speed, pressure and more between metric, imperial and US customary units, then check the maths yourself.

13measurement categories
30+units in length alone
100+ready-made conversion pages
0signups needed

The UntangleTools Unit Converter turns a number in one unit into the same quantity in another, across 13 categories: length, mass, volume, time, temperature, power, force, energy, speed, pressure, area, angle and data storage. Type a value, choose the unit you have, and the page lists what it equals in every other unit of that category at once, so you rarely need a second search.

It is built for people who hit a unit wall halfway through a task: a home cook holding an American recipe and a metric jug, a student checking a physics answer, an engineer reading a datasheet from another country, a traveller trying to judge a foreign speed limit, a seller sizing a parcel for international shipping, or anyone comparing a spec sheet in inches with a shop listing in centimetres.

What makes a converter trustworthy is not the arithmetic, which is just multiplication. It is knowing which definition applies. A gallon is not one size, a cup is not one size, and a gigabyte can mean two different numbers. The sections below explain those traps in plain language, show the working behind common conversions, and walk through real examples with the maths done out, so you can verify any result on this page.

What you get

What the UntangleTools Converter Gives You

Every unit at a glance

Enter one value and see its equivalent in every unit of the category in a single list. Comparing metres against feet, yards and miles takes one look instead of four searches.

One-tap copy

Tap any answer to copy the value, ready to paste into a spreadsheet, a recipe note or a message.

Two ways to pick

Use the Classic Picker for a quick From and To conversion, or the List Explorer when you want to browse everything.

Notes on every unit

Under the converter, each unit has a short definition, a formula, a practical use and the most common mistake people make with it.

Ready-made pair pages

Popular conversions such as cm to inches, kg to lbs and psi to bar have their own pages, linked from the common conversions list.

Instant, in your browser

The conversion maths runs on your device, so answers appear as you type without waiting for a server. Eight colour themes let you change the look to suit your screen and your eyes.

How to use

How to Use the Unit Converter in 5 Steps

Converting takes about ten seconds once you know the flow. Here is the full sequence, including the checks that stop the usual mistakes.

1
Pick the category
Choose what you are measuring from the category row: Length, Mass, Volume, Time, Temperature, Power, Force, Energy, Speed, Pressure, Area, Angle or Data Storage. Units only convert within a category, so metres can become feet but never kilograms.
2
Enter your value and the From unit
Type the number you have into the value box and select its unit in the From menu. Use a decimal point for fractions, so 2 and a half inches is entered as 2.5.
3
Choose the To unit
Select the unit you want in the To menu and the main answer updates straight away. If you are not sure which unit you need, skip ahead: the all-conversions list shows your value in every available unit.
4
Read, copy and compare
Read the headline result, then scan the list of every other unit. Tap a value to copy it. Very large or very small answers appear in scientific notation, so 1.000000e+18 means 1 followed by 18 zeros.
5
Sanity-check the answer
Open the notes under the converter for the formula and a mental benchmark, or look at the common-values table. A quick check catches the classic slips: swapping From and To, mixing US and imperial gallons, or reading a gigabyte as 1,024 megabytes when the label means 1,000.

Try the maths yourself

Pick a pair, change the number and watch the working update.

Value in cm

66.929134 in

170 ÷ 2.54 = 66.929134

The inch is exactly 2.54 cm by definition, so there is no rounding hiding in the factor.

How it works

Why Some Conversions Are Exact and Others Are Not

Most conversions are a single multiplication. A handful are exact because people defined them that way. The inch is 2.54 centimetres by agreement, not by measurement, and the pound is 0.45359237 kilograms. Those factors never change, so a calculator can give you every digit. The habit that follows is simple: keep the full factor while you calculate and round once, at the end.

Here is why. Convert 5 miles to kilometres with the exact factor 1.609344 and you get 8.04672 km. Round the factor to 1.6 first and you get 8 km, about 0.6% short. Round it to 1.61 and you get 8.05 km. Each slip looks harmless, but chain three of them and the error compounds.

Temperature is the exception to the multiply-only rule. Celsius and Fahrenheit differ in where zero sits as well as in the size of a degree, so you scale and then shift: °F equals °C times 9/5 plus 32. That is why 0 °C is 32 °F, and why −40 is the one temperature where both scales agree. The shift applies to readings only. A rise of 10 °C is a rise of 18 °F, because a difference has no zero point to move.

The 13 categories

What to Watch For in Each Measurement Category

Every category has one habit that trips people up. Here is the short version, written from the definitions rather than from habit.

Length

Anchored on the metre, defined from the speed of light. The inch is exactly 2.54 cm, the foot 0.3048 m and the mile 1,609.344 m. The old US survey foot, two parts per million longer, was retired on 31 December 2022.

Mass

Anchored on the kilogram, defined through the Planck constant since 2019. One pound is exactly 0.45359237 kg. Watch for troy ounces, used for precious metals, which are heavier than the ounces in a kitchen.

Volume

A US gallon is 3.785 L and an imperial gallon 4.546 L. Cups differ too: 236.588 mL, 240 mL on US nutrition labels, 250 mL in Australia, Canada and New Zealand. A fluid ounce measures space, not weight.

Time

Seconds, minutes and hours are fixed, but months and years are not. A common year has 365 days, a leap year 366, and astronomers use a 365.25 day Julian year for light-years. Say which year you mean.

Temperature

Kelvin is written without a degree sign. Celsius and Fahrenheit need a shift as well as a scale. Absolute zero is −273.15 °C or −459.67 °F, and the two everyday scales agree at −40.

Power

Watts measure a rate. Mechanical horsepower is 745.7 W while metric horsepower is 735.5 W, so check which one a car or motor rating uses. Do not confuse kilowatts with kilowatt-hours.

Force

A kilogram-force is the weight of one kilogram under standard gravity, 9.80665 N. A pound-force is about 4.448 N. Newtons measure force, kilograms measure mass, and mixing them once cost NASA a spacecraft.

Energy

One kilowatt-hour is exactly 3.6 megajoules. A food Calorie is a kilocalorie, 4,184 J, while a lowercase calorie is 4.184 J. BTUs also come in several definitions, so note which one you are using.

m/s

Speed

Multiply metres per second by 3.6 to get km/h, exactly. A knot is one nautical mile per hour, 1.852 km/h. Divide km/h by 1.609344 for mph, which is the conversion that matters on foreign roads.

Pressure

One bar is exactly 100 kPa, one standard atmosphere is 101.325 kPa and one psi is about 6.895 kPa. Tyre gauges read relative to the surrounding air (gauge pressure), while some engineering tables use absolute pressure.

m²

Area

Square the linear factor. If 1 ft is 0.3048 m, then 1 ft² is 0.09290304 m². An acre is exactly 4,046.8564224 m² and a hectare is 10,000 m².

rad

Angle

A full turn is 360 degrees, 2 pi radians or 400 gradians. Much software expects radians, so a correct angle in degrees can still give a wrong answer if the mode is wrong.

Data storage

Eight bits make a byte. Drive makers count in decimal (1 GB is 1,000,000,000 bytes) while many systems report binary sizes (1 GiB is 1,073,741,824 bytes). Network speeds in Mbps are bits, file sizes in MB are bytes.

Same name, different size

US Customary vs UK Imperial: Units That Share a Name

These are the conversions that go wrong most often, because both sides use the same word for different amounts.

Unit	US customary	UK imperial	The gap
Gallon	3.785 L	4.546 L	UK is about 20% larger
Pint	473.18 mL	568.26 mL	UK is about 20% larger
Fluid ounce	29.57 mL	28.41 mL	US is about 4% larger
Cup	236.59 mL (240 mL on labels)	284.13 mL (older recipes)	Metric cup is 250 mL
Ton	Short ton, 907.18 kg	Long ton, 1,016.05 kg	Metric tonne is 1,000 kg

Not everything differs. The foot, yard, mile and pound are the same in both systems, fixed by the 1959 international agreement. The metric cup used in Australia, Canada and New Zealand is 250 mL.

Quick estimates

Mental Maths Shortcuts and How Far Off They Are

Estimates are fine when you only need a ballpark. These are the ones people use most, with honest error sizes so you know when to reach for the converter instead.

km to mi
× 0.6
exact: × 0.621371
about 3% low
mi to km
× 1.6
exact: × 1.609344
about 0.6% low
kg to lb
× 2.2
exact: × 2.20462
about 0.2% low
cm to in
× 0.4
exact: × 0.393701
about 1.6% high
°C to °F
double, add 30
exact: × 1.8 + 32
within 4 °F from 0 to 30 °C
L to US gal
÷ 4
exact: ÷ 3.785
about 5% low
m/s to km/h
× 3.6
exact: × 3.6
no error at all
mL to US fl oz
÷ 30
exact: ÷ 29.57
about 1.4% low

Real-world examples

Everyday Conversions, Worked Out

Eight situations where a conversion decides something, with the arithmetic shown so you can repeat it.

Will the new TV fit on the shelf?
65 in diagonal
→ 143.9 cm wide
A television is sold by its diagonal. On a 16:9 screen the width is about 56.7 inches, and 56.7 × 2.54 gives 143.9 cm. A 150 cm shelf leaves roughly 3 cm on each side, provided the stand feet are not wider than the screen.
Following an American recipe
1.5 US cups
→ 354.9 mL
1.5 × 236.588 is 354.9 mL, so most cooks measure 355 mL. On a 240 mL label cup it would be 360 mL, and with a 250 mL metric cup it becomes 375 mL. For soup that hardly matters. For bread or cake, weigh ingredients whenever the recipe offers grams.
Reading a speed limit abroad
65 mph
→ 104.6 km/h
65 × 1.609344 gives 104.6 km/h. In the other direction, a 130 km/h motorway limit common in parts of Europe is 80.8 mph. Rental car dashboards often show both, but the road signs only show one.
Body weight in two systems
165 lb
→ 74.8 kg
165 × 0.45359237 is 74.84 kg, and the 2.2 shortcut gives 75 kg. That is fine for tracking fitness. For medicine, never rely on a general converter: use the units printed on the prescription label and ask a pharmacist.
Running an electric heater
1.5 kW for 4 h
→ 6 kWh = 21.6 MJ
Power times time gives energy: 1.5 × 4 is 6 kWh. Since 1 kWh is exactly 3.6 MJ, that is 21.6 megajoules. Your bill counts kWh, while the heater label shows kW or watts.
Inflating a tyre
32 psi
→ 2.21 bar = 220.6 kPa
One psi is 6.894757 kPa, so 32 psi is 220.6 kPa, and dividing by 100 gives 2.21 bar. European pumps usually show bar, American ones psi, and the car door sticker may show both.
A hard drive that looks too small
4 TB drive
→ 3.64 TiB
The maker counts 4 × 10¹² bytes. An operating system dividing by 2⁴⁰ shows about 3.64, and some label that figure TB. Nothing is missing. Two counting systems simply meet on one screen.
Comparing flat sizes
1,200 sq ft
→ 111.5 m²
Area scales with the square of length, so the factor is 0.3048 squared, which is 0.09290304. 1,200 × 0.09290304 is 111.48 m². A 2.5 acre plot is 1.01 hectares, since an acre is 0.4046856 hectares.

Why it matters

When Unit Mistakes Get Expensive

4.45x

Mars Climate Orbiter, September 1999

Ground software reported thruster impulse in pound-force seconds, while navigation software expected newton-seconds. One pound-force is 4.45 newtons, so the effect of each firing was underestimated by that factor. The orbiter reached Mars on a path that was too low, and the spacecraft, which cost about 125 million dollars, was lost.

22,300 kg

Gimli Glider, July 1983

Air Canada flight 143 needed 22,300 kg of fuel. The load was calculated with a density in pounds per litre (1.77) instead of kilograms per litre (about 0.8), so the Boeing 767 took off with roughly 10,100 kg. Both engines stopped at 41,000 feet, and the crew glided to a safe landing at Gimli, Manitoba.

2 ppm

The US survey foot, retired 2022

Two nearly identical feet differed by about one eighth of an inch per mile. Invisible on a floor plan, significant across a state survey.

931 GiB

A 1 TB drive

10¹² bytes divided by 2³⁰ is about 931. Same drive, two counting systems.

The lesson repeats every time: write the unit beside every number, and convert once, in one place.

Context

Metric or Imperial? Who Uses What, and How We Got Here

Today the metric system, formally the International System of Units or SI, is the legal or official system in almost every country. The United States, Liberia and Myanmar are the three most often listed as not having officially adopted it, although NIST points out that US law has allowed metric units since 1866 and that SI is built into American science, medicine and industry.

Daily life is messier than law. The UK signs its roads in miles and pours pints, while most packaged food is labelled in grams and litres. Canada weighs babies in kilograms and describes adult height in feet and inches. That mixed reality is exactly why people keep needing conversions.

1799
France deposits platinum standards for the metre and the kilogram in Paris, the foundation of the metric system.
1866
US law makes the metric system legal for use in trade and commerce.
1875
The Metre Convention is signed in Paris by 17 nations, including the United States.
1959
Six English-speaking nations agree on the international yard (0.9144 m) and pound (0.45359237 kg).
1960
The International System of Units, SI, is formally named at the 11th General Conference on Weights and Measures.
1983
The metre is redefined as the distance light travels in a vacuum in 1/299,792,458 of a second.
2019
On 20 May the kilogram, ampere, kelvin and mole are redefined using fixed physical constants, so all seven SI base units now rest on constants of nature.
2022
The US retires the survey foot on 31 December, leaving a single definition of the foot.

FAQ

Unit Conversion Questions, Answered

Short, direct answers to the conversion questions people search for most, plus a few about how this converter behaves.

How many centimetres are in an inch?

One inch is exactly 2.54 centimetres. The figure is a definition, fixed by the 1959 international yard and pound agreement, not a measurement that can be refined later. To convert inches to centimetres, multiply by 2.54. To go the other way, divide by 2.54. So a 27 inch monitor has a 68.58 cm diagonal, and a 170 cm person is about 66.9 inches tall, or 5 ft 6.9 in.

How do I convert kg to lbs?

Multiply kilograms by 2.20462 to get pounds. The pound is defined as exactly 0.45359237 kg, so you can also divide kilograms by 0.45359237 for the full-precision result. For example, 70 kg is 154.32 lb. In your head, multiply by 2.2: 70 × 2.2 is 154, off by only about 0.2%. For pounds to kilograms, divide by 2.2046 or multiply by 0.4536.

How do I convert Celsius to Fahrenheit and back?

Use °F = °C × 9/5 + 32 and °C = (°F − 32) × 5/9. Both steps matter because the scales start at different points as well as using different degree sizes. Handy checks: 0 °C is 32 °F, 37 °C is 98.6 °F, 100 °C is 212 °F, and −40 is the same on both scales. A common oven setting of 350 °F works out to 176.7 °C. For kelvin, add 273.15 to the Celsius value.

What is the difference between a US gallon and an imperial gallon?

They are different sizes. A US gallon is 3.785 litres (231 cubic inches), while an imperial (UK) gallon is 4.546 litres, about 20% more. The pints inside them differ in the same way: 473 mL in the US and 568 mL in the UK. This matters most for fuel economy, where 30 mpg in US gallons and 30 mpg in imperial gallons describe different efficiencies, and for older British recipes. Always confirm which gallon a source uses before converting.

How many millilitres are in a cup?

It depends on the cup. A US customary cup is 236.588 mL. US nutrition labels round a cup to 240 mL. Australia, Canada and New Zealand use a 250 mL metric cup, and old UK imperial cups were about 284 mL. For one cup the gap is small, but scale a recipe to eight cups and you can end up 100 mL apart. When a recipe gives millilitres or grams as well as cups, trust the metric figure.

Is 1 GB equal to 1,000 MB or 1,024 MB?

Both answers exist because two standards share one prefix. In the SI system, which drive makers and many networks follow, 1 GB is 1,000 MB and 1 MB is 1,000,000 bytes. Memory and several operating systems have traditionally counted in powers of 1,024, where the unit is properly called a gibibyte (GiB) and equals 1,073,741,824 bytes. That is why a 1 TB drive, holding 10¹² bytes, appears as about 931 GiB. Nothing is missing; the two systems count differently.

How do I convert km/h to mph?

Divide kilometres per hour by 1.609344 to get miles per hour. For a quick estimate, multiply by 0.6. A speed of 100 km/h is 62.14 mph, and 130 km/h is 80.8 mph. Going the other way, multiply mph by 1.609344, so 65 mph is 104.6 km/h. Metres per second convert to km/h by multiplying by exactly 3.6.

How do I convert square feet to square metres?

Multiply square feet by 0.09290304. The factor is the square of 0.3048, because area scales with the square of length. A 1,200 sq ft flat is 111.5 m². For a fast estimate divide square feet by 10.76, or by 10 if you only need a rough size. To go back, multiply square metres by 10.7639.

What is the difference between mass and weight, and does it affect conversions?

Mass is the amount of matter and is measured in kilograms or pounds. Weight is the force gravity exerts on that mass, measured in newtons or pounds-force. Your mass is the same on the Moon, but you would weigh about one sixth as much. In daily life people say weight and mean mass, so kg to lb is fine. Engineers keep them apart: converting kgf to newtons (multiply by 9.80665) is a force conversion, while kg to lb is a mass conversion.

How many feet are in a mile, and how many metres?

A mile is 5,280 feet, 1,760 yards or exactly 1,609.344 metres. The figure follows from the foot being exactly 0.3048 metres. A nautical mile is a different unit, 1,852 metres or about 6,076 feet, used at sea and in the air together with knots. Surveyors once used a slightly longer US survey foot, which the US retired on 31 December 2022.

What is the difference between kW and kWh?

A kilowatt (kW) is a rate of using energy, like speed. A kilowatt-hour (kWh) is an amount of energy, like distance. A 1.5 kW heater running for 4 hours uses 6 kWh, which is 21.6 megajoules because 1 kWh is exactly 3.6 MJ. Electricity bills charge for kWh, while appliance labels usually show kW or watts. For engines, 1 kW is about 1.341 mechanical horsepower and 1.360 metric horsepower.

How do I convert psi to bar and kPa?

One bar is exactly 100 kPa, and one psi is about 6.895 kPa, so 1 bar is about 14.504 psi. A tyre at 32 psi is 2.21 bar or 220.6 kPa. Also check whether a reading is gauge pressure, measured relative to the surrounding air, or absolute pressure, which includes the atmosphere at roughly 101.3 kPa. Tyre gauges almost always show gauge pressure.

Which countries still use imperial or US customary units?

The United States, Liberia and Myanmar are the three countries most often listed as not having officially adopted the metric system. NIST notes that US law has allowed metric use since 1866 and that SI is widely used in American science and industry. Other countries mix systems in daily life: the UK uses miles on roads and pints in pubs, and Canada still talks about height in feet and inches. So conversions between systems remain a daily need.

Why do some results appear in scientific notation, like 1.000000e+18?

Very large and very small answers switch to scientific notation so they stay readable. The part after the e is a power of ten: e+18 means multiply by 10¹⁸, moving the decimal point 18 places to the right, and e-9 means multiply by 10⁻⁹, moving it 9 places left. For example, 1 metre is 1.000000e+18 attometres, and 1 metre is 1.000000e-9 gigametres.

What are Planck length, parsec and Bohr radius in the length converter?

They are units for the extremes of scale. The Bohr radius is about 5.29 × 10⁻¹¹ m, the typical radius of a hydrogen atom in its lowest energy state, and the Planck length is about 1.6 × 10⁻³⁵ m, a theoretical scale in quantum physics. At the large end, the astronomical unit is exactly 149,597,870,700 m (the average Earth to Sun distance), a light-year is about 9.46 × 10¹⁵ m, and a parsec is about 3.086 × 10¹⁶ m, or 3.26 light-years. Most people only need metres, feet and miles, but the same method works at every scale.

Is an online unit converter accurate enough for medicine, engineering or legal work?

For everyday use, study, cooking, travel and rough engineering estimates, yes, provided you pick the right unit definitions. For anything where an error could hurt someone or carry legal weight, such as drug doses, structural design or calibration certificates, use the units printed on the official document, work from the standard that applies to your field and have a qualified person check it. A converter does the arithmetic, but it cannot know which gallon, cup or pound your source meant.

Does the unit converter need an account, and where is the maths done?

No account is needed. The conversion maths runs in your browser, so results appear instantly without waiting for a server, and the converter is free to use for as many conversions as you like.

Unit Converter

"1" Meter

How to Convert Meter to Centimeter

Meter to Centimeter — Common Values

About Meter (m)

About Centimeter (cm)

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UntangleTools

Every unit at a glance

One-tap copy

Two ways to pick

Notes on every unit

Ready-made pair pages

Instant, in your browser

Pick the category

Enter your value and the From unit

Choose the To unit

Read, copy and compare

Sanity-check the answer

Try the maths yourself

Length

Mass

Volume

Time

Temperature

Power

Force