# Horsepower to kilowatts converter

> Convert horsepower to kilowatts (hp to kW) with the exact factor, a conversion chart and worked steps.

Interactive version: https://www.calcopenly.com/conversion/hp-to-kw
Subject: Unit converters

A horsepower specification may describe an engine or motor. This conversion uses mechanical horsepower, which differs from metric PS. Compare the same kind of rating and test conditions: peak engine output and continuous electrical power are not interchangeable specifications.

One horsepower is about 0.7456998716 kilowatts, so 150 hp is 111.854981 kW. To convert hp to kW, multiply by 0.7456998716; to convert back, multiply by 1.3410220896.

Mechanical horsepower is 550 foot-pounds per second, about 745.7 W; metric horsepower (PS) is 735.49875 W. The factor has no exact decimal form, so results are computed with 50 significant digits and rounded only for display.

## Inputs

- **Horsepower (hp)**

## Results

- Kilowatts (kW) — main result
- Conversion
- 1 kW in horsepower (hp)

## Formula

$$
\text{kilowatts} = \text{horsepower} \times 0.745699871582
$$

## Worked examples

### 150 hp to kW

- Horsepower (hp): 150 hp
- **Kilowatts: 111.854980737 kW**
- Checked against: Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions)

### 400 hp to kW

- Horsepower (hp): 400 hp
- **Kilowatts: 298.279948633 kW**
- Checked against: Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions)

### 50 hp to kW

- Horsepower (hp): 50 hp
- **Kilowatts: 37.2849935791 kW**
- Checked against: Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions)

## Questions

### When would I convert hp to kW?

A horsepower specification may describe an engine or motor. This conversion uses mechanical horsepower, which differs from metric PS. Compare the same kind of rating and test conditions: peak engine output and continuous electrical power are not interchangeable specifications.

### How many kilowatts are in a horsepower?

One horsepower is about 0.7456998716 kilowatts. Mechanical horsepower is 550 foot-pounds per second, about 745.7 W; metric horsepower (PS) is 735.49875 W.

### How do you convert hp to kW?

Multiply the number of horsepower by 0.7456998716. For example, 150 hp × 0.7456998716 = 111.854981 kW. To go the other way, divide by 0.7456998716.

### How can I estimate hp to kW without a calculator?

Multiply by 0.75. That is 0.6% high of the exact factor 0.7456998716, so 150 hp comes out as 112.5 kW instead of 111.855.

### How accurate is the horsepower to kilowatts converter?

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 3 worked examples whose answers come from independent sources; for example, “150 hp to kW” is checked against Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions).

### Where does the method come from?

NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B; NIST Handbook 44, Appendix C: General tables of units of measurement; BIPM, The International System of Units (SI Brochure), 9th edition.

## Sources

- [NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B](https://www.nist.gov/pml/special-publication-811)
- [NIST Handbook 44, Appendix C: General tables of units of measurement](https://www.nist.gov/pml/weights-and-measures/publications/nist-handbooks/handbook-44)
- [BIPM, The International System of Units (SI Brochure), 9th edition](https://www.bipm.org/en/publications/si-brochure)