Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin, Rankine, Réaumur, and Delisle instantly. From everyday weather and cooking to cryogenic science and aerospace engineering type once, copy any result in one click.
6
Scales Supported
0 K → ∞
Full Range
Instant
All Outputs
Free
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Six Temperature Scales, One Converter
Every supported scale with its origin, defining anchors, absolute zero value, and primary use today
°C−273.15 °CCentigrade-based; 1 degree = 1 Kelvin step
°F−459.67 °F180 °F spans the freeze–boil range vs 100 °C
K0 KSI base unit; same step size as Celsius
°R0 °RAbsolute scale with Fahrenheit-sized degree steps
°Ré−218.52 °RéOctagesimal scale; still referenced in food science
°De559.725 °DeInverted scale higher °De means colder
Temperature Landmarks You Actually Encounter
From absolute zero to the surface of the Sun temperatures across all 3 major scales at once
| Landmark | °C | °F | K | Context |
|---|---|---|---|---|
| Absolute Zero | −273.15 | −459.67 | 0 | Coldest theoretically possible temperature |
| Liquid Nitrogen | −195.79 | −320.42 | 77.36 | Boiling point of N₂ at 1 atm |
| Dry Ice (CO₂) | −78.5 | −109.3 | 194.65 | Sublimation point of solid CO₂ |
| Water Freezes | 0 | 32 | 273.15 | Ice–liquid boundary at 1 atm |
| Comfortable Room | 22 | 71.6 | 295.15 | Typical indoor comfort zone |
| Human Body | 37 | 98.6 | 310.15 | Normal core body temperature |
| Water Boils | 100 | 212 | 373.15 | Liquid–vapour boundary at 1 atm |
| Oven: Baking | 180 | 356 | 453.15 | Typical bread and cake baking temp |
| Oven: Self-Clean | 482 | 900 | 755.15 | Pyrolytic oven self-clean cycle |
| Steel Melts | 1,370 | 2,500 | 1,643 | Approximate melting point of steel |
| Sun Surface | 5,505 | 9,941 | 5,778 | Photosphere of the Sun |
Why −40 matters: −40 °C and −40 °F are numerically identical the only crossover point of the two scales. Above −40, Fahrenheit always reads higher than Celsius; below −40, Fahrenheit values are less negative. This is a mathematical quirk of their different interval sizes (1 °F = 5/9 °C) and offset zero points not a physically significant threshold.
°C to °F Eight Values You'll Use Every Day
The most-looked-up temperature conversions, at a glance no formula needed
Only point where °C = °F
Water freezing point
Cold morning
Room temperature
Warm summer day
Body temperature
Dangerous fever threshold
Water boiling point
Exact Conversion Formulas for Every Scale Pair
All multipliers, offsets, and direction-specific expressions use these to manually verify any result
| Convert | Formula | Example |
|---|---|---|
| °C → °F | (°C × 9/5) + 32 | 100 °C = 212 °F |
| °F → °C | (°F − 32) × 5/9 | 98.6 °F = 37 °C |
| °C → K | °C + 273.15 | 0 °C = 273.15 K |
| K → °C | K − 273.15 | 373.15 K = 100 °C |
| °F → K | (°F + 459.67) × 5/9 | 32 °F = 255.37 K |
| K → °F | K × 9/5 − 459.67 | 300 K = 80.33 °F |
| °C → °R | (°C + 273.15) × 9/5 | 0 °C = 491.67 °R |
| °C → °Ré | °C × 4/5 | 100 °C = 80 °Ré |
| °Ré → °C | °Ré × 5/4 | 80 °Ré = 100 °C |
| °C → °De | (100 − °C) × 3/2 | 0 °C = 150 °De |
| °F → °R | °F + 459.67 | 72 °F = 531.67 °R |
| °R → K | °R × 5/9 | 491.67 °R = 273.15 K |
Why the 9/5 ratio? The Celsius scale spans 100 degrees between water's freeze and boil points. Fahrenheit spans 180 degrees across the same range. The ratio 180/100 = 9/5 = 1.8 is the exact interval conversion factor. The +32 / −32 offset accounts for the different zero points 0 °C vs 32 °F at water's freezing point.
Temperature Conversion Across Every Context
Cooking, healthcare, scientific research, and daily travel one tool handles them all
Cooking & Food Science
Recipes switch constantly between Celsius and Fahrenheit depending on the source's origin. Oven temperatures, candy stages, meat internal temps, and sous-vide precision all require fast, accurate conversion. Off by 20 °F in a bake and texture is ruined.
Healthcare & Pharmacology
Clinical thermometers, drug storage guidelines, and patient records use Celsius in most countries but Fahrenheit in the US. A nurse converting a fever of 38.5 °C, or a pharmacist checking a cold-chain limit of 46 °F, needs an instant answer not an approximation.
Science & Engineering
Physics and chemistry use Kelvin exclusively thermodynamic equations break down with negative temperatures. Engineers in the US may still work in Rankine for heat-transfer calculations. Researchers converting spectrometer readings, reactor temperatures, or cryogenic storage specs jump between all four absolute and relative scales.
Travel & Daily Weather
Travellers moving between the US and the rest of the world encounter a daily unit switch. A forecast of 95 °F in Phoenix reads as 35 °C; −10 °C in Oslo reads as 14 °F. Quick mental anchors help but exact conversion removes all ambiguity for packing decisions, outdoor plans, and local safety thresholds.
Temperature Conversion Questions Answered
Celsius, Fahrenheit, Kelvin, Rankine, Réaumur, Delisle formulas, science, and practical answers
Core Temperature Conversions
Multiply by 9, divide by 5, then add 32: (°C × 9/5) + 32 = °F. Example: 25 °C = 77 °F (25 × 1.8 + 32). Quick mental shortcut: double the Celsius, subtract 10 %, add 32. Example: 20 °C → 40 − 4 + 32 = 68 °F (exact). The tool gives the precise result instantly no mental arithmetic required.
Subtract 32, multiply by 5, then divide by 9: (°F − 32) × 5/9 = °C. Example: 98.6 °F = 37 °C exactly. Shortcut: subtract 32, then divide by 1.8. Example: 68 °F → 36 ÷ 1.8 = 20 °C. The formula works for all values including negatives enter −40 °F and you get −40 °C, the one point where both scales intersect.
Add 273.15: °C + 273.15 = K. Example: 0 °C = 273.15 K; 100 °C = 373.15 K. Kelvin matters because it is the SI base unit of thermodynamic temperature equations in physics and chemistry (gas laws, radiation laws, entropy) require an absolute scale with no negative values. A temperature of 0 K (absolute zero, −273.15 °C) is the point where molecular motion theoretically ceases entirely.
0 °C = 32 °F the freezing point of pure water at sea level. 100 °C = 212 °F the boiling point of pure water at 1 atm. These are the two defining anchors of the Celsius scale. The 180 °F range between freeze and boil equals exactly 100 °C, meaning 1 °C = 1.8 °F in terms of interval size. Kelvin equivalents: 0 °C = 273.15 K, 100 °C = 373.15 K.
Three steps: (1) Type any temperature value integers and decimals work (e.g., 36.6 °C, −10 °F, 300 K, 25.5 °Ré). (2) Select the source scale from the dropdown: °C, °F, K, °R, °Ré, or °De. (3) All other scales update instantly in the output panel. Tap the Copy button next to any result to copy it directly to your clipboard. No login, free at untangletools.com/unit/category/temperature.
Yes decimal inputs are fully supported. Examples: 36.6 °C → 97.88 °F (common thermometer reading); 98.2 °F → 36.78 °C; −17.5 °C → 0.5 °F. The tool uses 64-bit floating-point precision, so results are accurate to many decimal places. Fractions are equally valid enter 98 ½ as 98.5 and the conversion is exact.
Absolute zero is 0 K = −273.15 °C = −459.67 °F. It represents the theoretical minimum of thermodynamic temperature the state at which a system's particles have minimum possible kinetic energy. The third law of thermodynamics states that absolute zero can be approached but never fully reached in practice. The coldest temperatures ever achieved in laboratories are within billionths of a Kelvin above absolute zero, achieved through laser cooling and adiabatic demagnetisation.
Normal body temperature is approximately 37 °C / 98.6 °F. A fever begins around 38 °C / 100.4 °F. A high fever is 39–40 °C (102.2–104 °F). Above 40 °C / 104 °F is considered severe and warrants immediate medical attention; above 41.5 °C (106.7 °F), hyperthermia can cause organ damage. These thresholds apply to oral measurements rectal readings run ~0.3–0.5 °C higher.
How to Use the Tool
Temperature is an intensive property a measure of the average kinetic energy per particle in a substance, independent of amount. Heat is energy in transit, measured in joules or calories, and depends on the quantity of matter. Kelvin is essential for heat calculations because formulas like the Stefan–Boltzmann law (P = σT⁴) require absolute temperature inserting a negative Celsius value would produce a physically meaningless result.
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