100 hp in kW
- Value
- 100 hp
- From
- horsepower (hp)
- To
- kilowatt (kW)
- Converted value
- 74.5699871582 kW
- Exactness
- Exact
Checked against: 1 hp = 550 ft·lbf/s = 550 × 0.3048 × 4.4482216152605 W = 745.69987158227022 W (NIST SP 811 App. B)
Power converter
Convert hp to kW, kW to hp, watts to horsepower and BTU/h to tons of refrigeration, with mechanical (745.7 W) and metric (735.5 W) horsepower.
By AdminDrafted with AI writing toolsUpdated Checked examples: 5
Converted value
kW
Converted value: 74.5699871582 kW
- Conversion
- 100 hp ≈ 74.56999 kW
- Conversion factor
- 0.745699871582
- Exactness
- Exact
100 hp is about 74.56999 kW (exactly 74.569987158227022 kW). One horsepower is about 0.7456999 kW.
The same amount counted in each unit
100 hp in every Power unit
| Unit | Value | Definition |
|---|---|---|
| watt (W) | 74,569.99 | Base unit |
| milliwatt (mW) | 74,569,990 | 1 mW = 0.001 W, exact |
| kilowatt (kW) | 74.56999 | 1 kW = 1,000 W, exact |
| megawatt (MW) | 0.07456999 | 1 MW = 1,000,000 W, exact |
| gigawatt (GW) | 0.00007456999 | 1 GW = 1,000,000,000 W, exact |
| horsepower (hp) | 100 | 1 hp = 745.69987158227022 W, exact (Mechanical horsepower (550 ft·lbf/s)) |
| metric horsepower (PS) | 101.387 | 1 PS = 735.49875 W, exact |
| BTU per hour (BTU/h) | 254,443.4 | 1 BTU/h = 1,055.05585262/3,600 W, exact |
| ton of refrigeration (TR) | 21.20361 | 1 TR = 12,660,670.23144/3,600 W, exact |
| kilocalorie per hour (kcal/h) | 64,161.56 | 1 kcal/h = 4,184/3,600 W, exact |
How it's calculated S
Convert horsepower to watt
1 hp = 745.69987158227022 W, exact (Mechanical horsepower (550 ft·lbf/s))
Convert watt to kilowatt
1 kW = 1,000 W, exact
Combined factor
Both units are defined exactly and the converted mathematical value has a terminating decimal. A displayed result may still be rounded.
About the power converter
Every power unit is a fixed number of watts (joules per second). Mechanical horsepower is 550 foot-pounds-force per second, which works out at exactly 745.69987158227022 W; metric horsepower (PS) is 75 kilogram-force metres per second, exactly 735.49875 W. A ton of refrigeration is 12,000 BTU/h, about 3.517 kW.
The default converts a 100 hp engine to 74.57 kW. Car specifications are the usual reason: European registration documents give engine power in kW while brochures quote PS or hp, and 100 kW is 134.1 hp or 136.0 PS.
Air-conditioner ratings in BTU/h or tons describe cooling output, not the electricity drawn: a 1.5-ton unit moves 18,000 BTU/h (5.28 kW) of heat, and its electrical input depends on its efficiency rating.
How to convert hp to kW
Multiply mechanical horsepower by 0.7457: a 100 hp engine is 74.57 kW, since one hp is 550 ft·lbf/s, exactly 745.69987158227022 W. Metric horsepower (PS, CV or ch), common in European car specifications, is 735.49875 W, so 100 PS is 73.55 kW.
The mechanical value follows from the international foot and pound-force: 550 × 0.3048 m × 4.4482216152605 N = 745.69987158227022 W (NIST SP 811, Appendix B.9). Metric horsepower is 75 kgf·m/s: 75 × 9.80665 = 735.49875 W.
How to convert kW to hp
Multiply kilowatts by 1.341022 for mechanical hp, or by 1.359622 for PS. A 150 kW engine is 201.15 hp or 203.94 PS, and 100 kW is 134.10 hp or 135.96 PS.
hp, bhp, PS and electric horsepower
- hp and bhp use the same 745.7 W unit. "Brake" horsepower says where it was measured: at the engine's output shaft, before transmission losses.
- PS (Pferdestärke), also written CV or ch, is metric horsepower. One mechanical hp is 1.01387 PS, so 150 PS is 147.95 hp or 110.32 kW.
- Electric horsepower, used to rate electric motors, is exactly 746 W.
BTU/h and tons of refrigeration
Air conditioners and heaters are rated in BTU per hour. 1 kW = 3,412.14 BTU/h, so a 2 kW electric heater gives out 6,824 BTU/h, and 1 BTU/h is 0.293071 W.
A ton of refrigeration is 12,000 BTU/h, or 3.517 kW: the rate that melts one short ton of ice in a day, since 2,000 lb × 144 BTU/lb ÷ 24 h = 12,000 BTU/h. A 1.5-ton unit moves 18,000 BTU/h, which is 5.28 kW of heat.
That rating is cooling output. The electricity the unit draws is lower and depends on its efficiency rating, so the 5.28 kW is not the figure that drives the electricity bill.
Power conversion chart
Repeating decimals are rounded to six places. BTU/h uses the International Table BTU, and kcal/h the thermochemical kilocalorie.
| Value | From | To | Converted power |
|---|---|---|---|
| 100 | hp | kW | 74.569987 |
| 1 | kW | hp | 1.341022 |
| 1 | PS | W | 735.49875 |
| 12000 | BTU/h | TR | 1 |
| 1.5 | TR | kW | 5.275279 |
| 1 | kcal/h | W | 1.162222 |
kW vs kWh
Watts measure a rate of energy use; watt-hours measure the energy itself. A 2 kW device running for 3 hours uses 6 kWh. Convert kWh, BTU and joules with the energy converter.
Common mistakes
- Comparing hp and PS as if equal. The units differ by 1.4%: 200 PS is 197.26 hp.
- Confusing mW and MW. A milliwatt and a megawatt differ by a factor of 10⁹; the case of the m matters.
- Using 746 W for every horsepower. That is the electric horsepower, 0.04% above the mechanical one.
- Reading AC tons as weight or electrical input. A ton is 12,000 BTU/h of heat removed.
Related power tools
For one direction at a time, use hp to kW or kW to hp. The horsepower calculator finds horsepower from torque and rpm, and the air conditioner BTU calculator sizes a unit for a room.
Worked examples
1 kW in hp
- Value
- 1 kW
- From
- kilowatt (kW)
- To
- horsepower (hp)
- Converted value
- 1.3410220896 hp
Checked against: 1000 / 745.69987158227022
12,000 BTU/h is one ton of refrigeration
- Value
- 12,000 BTU/h
- From
- BTU per hour (BTU/h)
- To
- ton of refrigeration (TR)
- Converted value
- 1 TR
Checked against: 1 ton of refrigeration = 12,000 BTU/h (NIST SP 811 App. B)
Zero power
- Value
- 0 W
- From
- watt (W)
- To
- horsepower (hp)
- Converted value
- 0 hp
- Exactness
- Exact
Checked against: 0 × any factor = 0
Questions
How many watts are in a horsepower?
745.7 W for mechanical horsepower (550 ft·lbf/s), 735.5 W for metric horsepower (PS or CV), and exactly 746 W for the electric horsepower used to rate electric motors; NIST SP 811 lists all three. Mechanical and metric horsepower differ by 1.4%, enough to matter when comparing car figures.
How do I convert kW to hp?
Multiply by 1.34102 for mechanical horsepower or by 1.35962 for metric PS. A 150 kW engine is 201.2 hp or 203.9 PS. To go from hp to kW, multiply by 0.7457, so the default 100 hp is 74.57 kW.
What is the difference between hp, bhp and PS?
hp and bhp use the same 745.7 W unit; “brake” horsepower means the power was measured at the engine's output shaft, before transmission losses. PS (Pferdestärke) is metric horsepower, 735.5 W, also written CV or ch. A car quoted at 150 PS makes 147.9 hp or 110.3 kW.
What does a 1.5-ton air conditioner mean?
It removes 18,000 BTU of heat per hour, about 5.28 kW of cooling. A ton of refrigeration is 12,000 BTU/h. The traditional ice-melting calculation uses one short ton (2,000 lb) over 24 hours with an assumed 144 BTU per pound. The electricity drawn depends on efficiency; cooling output alone does not determine electrical input.
How many BTU/h is 1 kW?
3,412.14 BTU/h. One watt is 3.41214 BTU/h, so a 2 kW electric heater gives out 6,824 BTU/h, and a 12,000 BTU/h air conditioner is rated at 3.517 kW of cooling. The factor is the same as between kWh and BTU because both sides are divided by one hour.
About this calculator
Sources
Checked against references
This calculator includes 5 worked examples with independently sourced answers. They run in the test suite, and you can run them here too.