This power converter converts watts, kilowatts, horsepower, BTU per hour, foot-pounds per second and tons of refrigeration — the units of engines, appliances and air conditioners.
Horsepower: Two Species and a Sales Pitch
James Watt coined the horsepower to sell steam engines against the horses they replaced, and defined it generously (his engines won the comparison). Mechanical hp = 745.7 W; the metric PS (Pferdestärke) is 735.5 W — a 1.4% gap that car brochures exploit and this converter keeps separate and labeled. AC capacity in “tons” (1 ton = 12,000 BTU/h = 3,517 W) also lives here; the room that ton must cool is our BTU Calculator‘s problem. Total energy over time converts on the Energy Converter. Part of our Conversion Calculators collection.
Quick Reference
| 1 unit | = watts | 1 unit | = watts |
|---|---|---|---|
| 1 hp (mechanical) | 745.7 | 1 BTU/h | 0.293 |
| 1 PS (metric hp) | 735.5 | 1 ton of refrigeration | 3,516.9 |
| 1 kW | 1,000 (= 1.341 hp) | 1 ft·lb/s | 1.356 |
Worked Examples (Verified)
- A 300 hp car = 223.7 kW — the number European spec sheets print
- A 1,500 W space heater = 5,118 BTU/h — the math behind the box’s heating claims
- A human cyclist sustaining 250 W holds about 0.34 hp — Watt’s marketing flattered his engines and, accidentally, every athlete since
Related Tools
- Energy Converter — power × time
- BTU Calculator — sizing the AC itself
- Conversion Calculators — the full collection
Frequently Asked Questions
How many watts are in a horsepower?
745.7 W for mechanical (imperial) horsepower; 735.5 W for metric PS. Car specs differ by market — a “300 PS” German car is 296 mechanical hp.
How do I convert kW to hp?
Multiply kilowatts by 1.341. A 100 kW electric motor is a 134 hp motor — the conversion EV specs constantly invite.
What is a ton of air conditioning in watts?
3,517 W of cooling capacity (12,000 BTU/h) — the cooling from melting one ton of ice per day, historically. A “3-ton” home AC moves roughly 10.6 kW of heat.
BTU/h to watts — what’s the factor?
× 0.2931. A 10,000 BTU/h window AC delivers ≈ 2,931 W of cooling (its electrical draw is separate and lower — efficiency is the COP story).
Is horsepower still an official unit anywhere?
It persists in automotive and marine marketing (US, UK) and small-engine ratings; the watt/kilowatt is the SI standard and the only unit with a single definition — PS vs hp vs “boiler hp” (9,810 W!) is why converters earn their keep.
Is this power converter free?
Yes — free, instant, no sign-up.