Power Converter
Convert watts, kilowatts, horsepower, PS, and BTU per hour.
What it does
Power conversion multiplies by fixed factors between unit systems. The watt anchors science and bills, mechanical horsepower anchors engines, metric PS anchors European car specs, and BTU per hour anchors heating.
The tool above moves between five units: watts, kilowatts, mechanical hp, metric PS, and BTU/h. Pick both ends, enter the value, and every equivalent appears below the answer.
Watch the two horsepowers: mechanical hp is 745.699872 W while metric PS is 735.49875 W, about 1.4% smaller. A 100 PS car is only 98.6 hp, which matters when comparing spec sheets across borders.
Factors follow NIST Special Publication 811 conversion tables with Britannica horsepower references behind them. Mechanical hp traces to 550 foot pounds per second, fixed at 746 W electrical equivalent by early standards work.
How to use
- Enter the power value in the source unit.
- Pick the source unit on the left and the target on the right.
- Read the converted line first.
- Scan the all units note for the rest.
- Check which horsepower a spec sheet means before comparing.
Formula
- 745.699872
- Watts in one mechanical horsepower.
- 735.49875
- Watts in one metric PS.
- hub
- Watts as the single middle step for all pairs.
Boiler and electric horsepower variants differ and sit outside this page. BTU here is per hour (power), not total energy like the energy converter page.
Worked example
Example: 100 hp to watts
Value 100, from hp, to watts.
- Factor for hp: 745.699872 W each.
- Multiply: 100 x 745.699872 = 74569.9872 W.
- Kilowatts: 74569.9872 / 1000 = 74.57 kW.
- Result: 100 hp = 74569.9872 W.
- Reverse: 74569.9872 / 745.699872 = 100 hp back.
Reference table
| Pair | Factor | Everyday check |
|---|---|---|
| 1 hp to W | 745.699872 | Mower engine near 4 hp is 2983 W |
| 1 PS to hp | 0.9863 | 100 PS is 98.6 hp |
| 1 kW to BTU/h | 3412.1416 | Heater kilowatt is 3412 BTU/h |
| 1 hp to BTU/h | 2544.43 | Car 150 hp sheds 381,665 BTU/h |
Limits
- Mechanical and metric power only; boiler hp differs.
- BTU/h is power flow, not stored energy.
- Peak versus continuous ratings differ on motors.
- Efficiency losses sit outside unit math.
Common mistakes
- Reading PS as hp one to one (1.4% gap).
- Mixing BTU total energy with BTU/h power.
- Rounding 746 to 745 mid chain on large plants.
- Comparing peak motor watts with continuous ratings.
- Forgetting kilowatts to watts is times 1000.
Try it yourself
Quick checks. Answers sit tucked under each question.
2000 W in hp?
2000 / 745.699872 = 2.682 hp.
2 kW in BTU/h?
2000 / 0.29307107 = 6824.28 BTU/h.
150 hp in kW?
150 x 0.745699872 = 111.85 kW.
Questions
How many watts in a horsepower?
745.699872 W mechanical. Metric PS is 735.49875 W.
hp or PS?
US specs use hp, European use PS. Multiply PS by 0.9863 for hp.
kW to BTU/h?
Multiply by 3412.1416. A 2 kW heater is 6824 BTU/h.
What is boiler horsepower?
A separate 9810 W unit for steam plant rating, outside this page.
Why two horsepowers?
Watt British definition versus continental metric definition; standards kept both.
Power or energy?
Watts and hp flow per second; joules and kWh total it up. This page converts flows.