Power Unit ConverterW · kW · MW · hp · BTU/hr · mW · J/s
Convert any power unit instantly — kilowatts to horsepower, watts to BTU/hr, milliwatts to watts, megawatts to kilowatts. Covers electrical, mechanical, and thermal power standards. Built for students, electricians, HVAC engineers, and automotive professionals. Type once, copy any output.
All units in watts
Why Power Has Three Different Units
Watts, horsepower, and BTU/hr all measure power — but each evolved in a different engineering world
W / kW / MW
SI Electrical
Electricians, engineers, solar/EV industry
The watt (W) is the SI base unit for power. 1 W = 1 joule per second. Every electrical device rating, solar panel output, and EV charger speed is in watts (W) or kilowatts (kW). The global standard.
hp
Mechanical / Automotive
Automotive, pump/motor spec sheets, US market
Horsepower (hp) originated from comparing steam engines to horses. Mechanical hp = 745.7 W; electric hp = 746 W. Car engines, boat motors, and industrial pumps still use hp in the US and UK.
BTU/hr
Thermal / HVAC
HVAC engineers, AC buyers, boiler installers
BTU/hr measures heat transfer rate. Air conditioners, boilers, and heaters are rated in BTU/hr because they move heat, not just electricity. 1 W = 3.412 BTU/hr; 12,000 BTU/hr = 1 ton of cooling.
mW
Electronics / RF
Electronics engineers, RF/wireless, IoT designers
Milliwatts (mW) are used for low-power electronics — Bluetooth (2.5 mW), Wi-Fi transmitters (20–100 mW), IoT sensors (µW range). Power amplifiers often specify gain in dBm (decibels relative to 1 mW).
kW, hp, BTU/hr, W — All at Once
Six common power values shown in every unit simultaneously — the fastest reference on the web
| Input | Watts (W) | Horsepower (hp) | BTU/hr | Milliwatts (mW) |
|---|---|---|---|---|
1 kW | 1,000 W | 1.341 hp | 3,412 BTU/hr | 1,000,000 mW |
1 hp | 745.7 W | 1 hp | 2,545 BTU/hr | 745,700 mW |
1 MW | 1,000,000 W | 1,341 hp | 3,412,142 BTU/hr | 10⁹ mW |
1,000 BTU/hr | 293.1 W | 0.3930 hp | 1,000 BTU/hr | 293,071 mW |
100 W | 100 W | 0.1341 hp | 341.2 BTU/hr | 100,000 mW |
1 GW | 10⁹ W | 1,341,022 hp | 3.41×10⁹ BTU/hr | 10¹² mW |
1 watt = 1 joule per second. All values above use mechanical horsepower (1 hp = 745.7 W) and ISO BTU (1 BTU = 1055.06 J). AC "tons of cooling" = 12,000 BTU/hr = 3,517 W — enter any of these into the converter to get the rest.
Exact Formulas for Every Power Conversion
Use these to verify calculations or work offline — all factors are exact or ISO-defined
| Convert | Formula | Example |
|---|---|---|
| kW → hp | kW × 1.34102 | 75 kW = 100.6 hp |
| hp → kW | hp × 0.7457 | 300 hp = 223.7 kW |
| W → kW | W ÷ 1,000 | 2,500 W = 2.5 kW |
| kW → W | kW × 1,000 | 3.5 kW = 3,500 W |
| W → BTU/hr | W × 3.41214 | 1,000 W = 3,412 BTU/hr |
| BTU/hr → W | BTU/hr × 0.29307 | 12,000 BTU/hr = 3,517 W |
| BTU/hr → kW | BTU/hr ÷ 3,412.14 | 24,000 BTU = 7.034 kW |
| kW → BTU/hr | kW × 3,412.14 | 5 kW = 17,061 BTU/hr |
| hp → W | hp × 745.7 | 4 hp = 2,982.8 W |
| MW → kW | MW × 1,000 | 2.5 MW = 2,500 kW |
| W → mW | W × 1,000 | 5 W = 5,000 mW |
| mW → W | mW ÷ 1,000 | 500 mW = 0.5 W |
Common Appliances — W, kW, hp & BTU/hr
See power ratings you recognise expressed in every unit — instantly verify your conversions make physical sense
| Appliance / Device | Watts (W) | Kilowatts (kW) | Horsepower (hp) | BTU/hr |
|---|---|---|---|---|
| LED bulb | 8–15 W | 0.008–0.015 kW | ~0.013 hp | 27–51 BTU/hr |
| Laptop charger | 45–100 W | 0.045–0.1 kW | ~0.10 hp | 154–341 BTU/hr |
| Microwave oven | 600–1,200 W | 0.6–1.2 kW | ~1.1 hp | 2,047–4,094 BTU/hr |
| Hair dryer | 1,200–2,000 W | 1.2–2 kW | ~2.0 hp | 4,094–6,824 BTU/hr |
| Window AC (1 ton) | ~1,000 W | 1.0 kW | 1.34 hp | ~12,000 BTU/hr |
| Electric kettle | 2,000–3,000 W | 2–3 kW | ~3.5 hp | 6,824–10,236 BTU/hr |
| Electric car motor | 100,000+ W | 100–300 kW | 134–402 hp | 341,214+ BTU/hr |
| Wind turbine | ~2,000,000 W | 2,000 kW | 2,682 hp | 6.8M BTU/hr |
AC Sizing: BTU/hr, kW, and Tons Explained
Match your room size to the right cooling capacity — in every power unit your AC spec sheet uses
| Room Size | BTU/hr needed | kW | Tons |
|---|---|---|---|
| Small bedroom (100 sq ft) | 5,000–6,000 | 1.5–1.8 kW | 0.5 ton |
| Medium room (150–250 sq ft) | 6,000–8,000 | 1.8–2.3 kW | 0.75 ton |
| Large room (300–450 sq ft) | 10,000–12,000 | 2.9–3.5 kW | 1.0 ton |
| Open plan (500–700 sq ft) | 14,000–18,000 | 4.1–5.3 kW | 1.5 ton |
| Large hall (1,000+ sq ft) | 24,000–30,000 | 7.0–8.8 kW | 2.0–2.5 ton |
Key AC Conversions
EER vs kW: AC efficiency is measured as EER (Energy Efficiency Ratio) = BTU/hr output ÷ watts input. A 12,000 BTU/hr AC drawing 1,200 W has EER 10 — it delivers 10× more cooling BTU/hr than watts consumed.
Three Steps from Input to Clipboard
No configuration, no target-unit selection — just enter and copy
Enter a power value
Type or paste: 3.5 kW, 300 hp, 18,000 BTU/hr, 500 mW. Decimals fully supported.
Select the source unit
Pick from W, kW, MW, GW, hp, BTU/hr, mW, J/s. All outputs refresh instantly.
Copy any output
Tap Copy on any row — watts, kW, hp, BTU/hr — one press, straight to clipboard.
Power Conversion Questions Answered
Covering W, kW, MW, GW, hp, BTU/hr, mW, J/s — with exact factors, real examples, and AC sizing guidance
Core Power Conversions
Enter your kilowatt (kW) value, select kW as the source unit — the horsepower (hp) result appears instantly. Formula: kW × 1.34102 = hp. Example: 75 kW = 100.6 hp. In reverse: hp × 0.7457 = kW. Note: mechanical horsepower = 745.7 W; electric horsepower = 746 W exactly — both are selectable.
1 kilowatt (kW) = 1,000 watts (W). 1 megawatt (MW) = 1,000,000 W. In reverse: 1 W = 0.001 kW = 0.000001 MW. The watt (W) is the SI base unit of power — 1 watt equals 1 joule per second (J/s). All electrical devices, from a 10 W LED to a 100 MW power station, are measured in watts or its multiples.
Horsepower to kilowatts: hp × 0.7457 = kW. Example: 300 hp = 223.7 kW. Kilowatts to horsepower: kW × 1.34102 = hp. Example: 150 kW = 201.2 hp. This conversion is essential when comparing US car specs (hp) with European car specs (kW) — both describe the same engine output in different units.
Watts to horsepower: W ÷ 745.7 = hp. Example: 1,500 W = 2.01 hp. Horsepower to watts: hp × 745.7 = W. Example: 5 hp = 3,728.5 W. Common use: motor nameplates list hp; electrical panels specify W or kW. Converting between them confirms a motor draws the expected current at rated power.
BTU/hr to watts: BTU/hr × 0.29307 = W. Example: 12,000 BTU/hr = 3,517 W (≈ 3.5 kW). Watts to BTU/hr: W × 3.41214 = BTU/hr. Example: 1,000 W = 3,412 BTU/hr. Air conditioners are rated in BTU/hr while electrical consumption is in watts — this conversion tells you how much electricity an AC unit uses per hour.
Milliwatts to watts: mW ÷ 1,000 = W. Example: 500 mW = 0.5 W. Watts to milliwatts: W × 1,000 = mW. Example: 2.4 W = 2,400 mW. Milliwatts (mW) are used in RF transmitters, Bluetooth modules (≈2.5 mW), Wi-Fi radios (20–100 mW), and low-power IoT sensors. In dBm: 0 dBm = 1 mW; 30 dBm = 1,000 mW = 1 W.
1 watt (W) = 1 joule per second (J/s) — this is the definition of the watt. Therefore: 1 kW = 1,000 J/s; 1 MW = 1,000,000 J/s. Over time: 1 W for 1 hour = 3,600 joules = 1 watt-hour (Wh). This relationship connects power (watts) to energy (joules or kWh) — power × time = energy. Your electricity bill charges for kWh (energy), not kW (power).
UntangleTools Power Converter supports: milliwatt (mW), watt (W), kilowatt (kW), megawatt (MW), gigawatt (GW), mechanical horsepower (hp), electric horsepower (hp(e)), BTU per hour (BTU/hr), joule per second (J/s), calorie per second (cal/s), and foot-pound per second (ft·lbf/s). Enter any value, select unit, see all outputs. One-click copy. Free at untangletools.com/unit/category/power.
Kilowatts to megawatts: kW ÷ 1,000 = MW. Example: 2,500 kW = 2.5 MW. Megawatts to kilowatts: MW × 1,000 = kW. Example: 0.5 MW = 500 kW. Megawatts are the unit of choice for power stations, large wind turbines (~2–15 MW each), and national grid capacity. A typical UK home uses ~3–5 kW at peak — 0.003–0.005 MW.
1 mechanical horsepower = 745.7 watts (W). 100 hp = 74,570 W = 74.57 kW. Formula: hp × 745.7 = W or hp × 0.7457 = kW. 1 electric horsepower = 746 W exactly. Common reference: a 400 hp sports car = ~298 kW; a 1 hp water pump = 745.7 W. The converter distinguishes mechanical and electric hp — select the correct type for accurate results.
Using the Tool
Three steps: (1) Type or paste a power value — integer or decimal (e.g., 3.5 kW, 250 hp, 18,000 BTU/hr). (2) Select the source unit: W, kW, MW, GW, hp, BTU/hr, mW, J/s. (3) All outputs update instantly — no button needed. Tap Copy next to any row to copy that value directly to your clipboard for use in specs, reports, or calculations.
Yes. The converter handles all three domains simultaneously: mechanical (hp, ft·lbf/s) used in engines and motors, electrical (W, kW, MW, mW) used in appliances and grids, and thermal (BTU/hr, cal/s) used in HVAC and heat engineering. Enter any value in any domain and all units across all three systems appear in the output.
Yes — all of them plus more. Full unit support: mW, W, kW, MW, GW, hp (mechanical), hp (electric), BTU/hr, J/s, cal/s, ft·lbf/s. Every unit is selectable as source input. All others appear simultaneously as output. One-click copy on each row for fast paste-into-workflow use.
Yes. Decimal inputs are fully supported. Examples: 1.5 kW → 2.011 hp, 5,118 BTU/hr; 0.75 kW → 1.006 hp; 2,400 W → 3.218 hp → 8,189 BTU/hr. No rounding at input — full floating-point precision throughout. Useful for partial load calculations on motors, appliances running below rated power, and AC sizing for rooms.
Yes. All conversion factors use exact or internationally standardised values: 1 mechanical hp = 550 ft·lbf/s = 745.69987 W; 1 BTU = 1055.05585 J (ISO definition); 1 cal = 4.1868 J (IT calorie). Results use 64-bit floating-point precision. Completely free at untangletools.com/unit/category/power — no account, no limits.
Students, Electricians & HVAC
Multiply kilowatts by 1.34102: kW × 1.34102 = hp. Examples: 1 kW = 1.341 hp; 10 kW = 13.41 hp; 0.5 kW = 0.671 hp. In reverse: hp × 0.7457 = kW. The factor 1.34102 comes from 1,000 ÷ 745.7 — dividing one kilowatt by the watt value of one horsepower. Both kW and hp measure the same physical quantity (power) — just with different historical origins.
1.5 kW = 1,500 watts (W). 2 kW = 2,000 W. Formula: kW × 1,000 = W. More examples: 0.5 kW = 500 W; 3.5 kW = 3,500 W; 7.2 kW = 7,200 W (a typical home EV charger). In horsepower: 1.5 kW = 2.01 hp; 2 kW = 2.68 hp. In BTU/hr: 1.5 kW = 5,118 BTU/hr; 2 kW = 6,824 BTU/hr.
Divide watts by 1,000: W ÷ 1,000 = kW. Examples: 2,500 W motor = 2.5 kW; 750 W appliance = 0.75 kW; 100 W bulb = 0.1 kW. For three-phase motors: kW = (V × I × √3 × PF) ÷ 1,000 where PF is power factor (typically 0.85–0.95). The converter handles the kW↔W step — for motor calculations requiring voltage and current, use that formula first then convert here.
UntangleTools Power Converter covers every power scale in one place. For students: instant kW↔hp, W↔BTU/hr with the formula visible. For electricians: W↔kW↔MW for panel sizing and load calculations. For HVAC engineers: BTU/hr↔kW↔W for AC and boiler ratings. For automotive engineers: hp↔kW for engine specs. Free, no login, mobile-ready.
Yes. The tool is fully responsive with tap-friendly inputs and large Copy buttons. Open untangletools.com/unit/category/power in any mobile browser — Chrome, Safari, Firefox. Paste a BTU/hr rating from an AC product page or type a kW value from a motor nameplate — all outputs appear instantly. Ideal for on-site electricians, HVAC installers, and engineers checking specs away from a desk.
Automotive, HVAC & Advanced
BTU/hr to kW: BTU/hr ÷ 3,412.14 = kW. Common AC conversions: 12,000 BTU/hr = 3.517 kW (1 ton); 18,000 BTU/hr = 5.275 kW (1.5 ton); 24,000 BTU/hr = 7.034 kW (2 ton). In reverse: kW × 3,412.14 = BTU/hr. Air conditioners are rated in BTU/hr in the US and tons in India; European markets use kW. This converter lets you compare models across all three systems instantly.
BTU/hr to kW: BTU/hr ÷ 3,412.14 = kW. Example: 80,000 BTU/hr boiler = 23.45 kW. BTU/hr to watts: BTU/hr × 0.29307 = W. Example: 100,000 BTU/hr = 29,307 W ≈ 29.3 kW. Residential gas boilers in the US are rated in BTU/hr; UK and EU boilers use kW. A 24 kW combi boiler ≈ 81,888 BTU/hr. Use this converter to compare heating specs across international markets.
Horsepower to kW: hp × 0.7457 = kW. Common car conversions: 100 hp = 74.57 kW; 200 hp = 149.1 kW; 400 hp = 298.3 kW; 1,000 hp = 745.7 kW. European car specs show kW; US/UK specs show hp. Both describe the same engine output. A useful mental shortcut: 1 hp ≈ 0.75 kW (multiply hp by 0.75 for a fast rough estimate, accurate to ~0.4%).
All three measure the same physical quantity — rate of energy transfer (power) — but from different historical and engineering traditions. Watt (W) / kilowatt (kW) is the SI standard used in electrical engineering worldwide. Horsepower (hp) originated in mechanical engineering and persists in automotive and pump specs. BTU/hr comes from thermal engineering — it measures heat transfer rate rather than mechanical or electrical power. Exact relationships: 1 hp = 745.7 W = 2,545 BTU/hr; 1 kW = 1.341 hp = 3,412 BTU/hr.
Calorie per second (cal/s) is included — 1 cal/s = 4.1868 W. For reference: 1 erg/s = 10⁻⁷ W (extremely small — used in CGS physics). 1 ton of refrigeration = 3,517 W = 12,000 BTU/hr. 1 metric horsepower (PS, Pferdestärke) = 735.5 W (used in German car specs — slightly less than mechanical hp at 745.7 W). These advanced units are on the roadmap — bookmark untangletools.com/unit/category/power for updates.
More Converters on UntangleTools
All free, instant, no signup — the complete unit conversion toolkit
Energy Converter
kWh, joules, calories, BTU — energy vs power.
Try tool →Speed Converter
km/h, mph, m/s, knots — travel and physics.
Try tool →Mass Converter
kg to lb, g to oz, mg, stone, tonne.
Try tool →Temperature Converter
Celsius, Fahrenheit, Kelvin — instant.
Try tool →Data Storage Converter
GB to MB, TB to GB, bits to bytes.
Try tool →Time Converter
ns to years — seconds, minutes, hours, days.
Try tool →
