Convert Horsepower to Milliwatts
1 horsepower (hp) equals 745699.8716 milliwatts (mW).
1 hp = 745699.8716 mW
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk horsepower to milliwatt converter to paste a column from Excel.
How to Convert Horsepower to Milliwatt
- 1 hp = 745699.8716 mW
- 1 mW = 0.00000134102209 hp
- Example: convert 15 hp to mW: 15 hp = 15 × 745699.8716 mW = 11185498.07 mW
Reference conditions. hp: Mechanical (imperial) horsepower, 550 ft·lbf/s. Metric horsepower (PS) is about 1.4 % smaller.
Formula
mW = hp × 745699.8715823
Derivation from SI units:
- 1 hp = 550 ft·lbf/s = 745.69987158227 W
- 1 mW = 10⁻³ W
- 1 hp = 745.6998715823 W ÷ 0.001 W per mW = 745699.8715823 mW
Both units are defined exactly, so the factor is exact. Horsepower definition: horsepower; Milliwatt definition: milliwatt.
Worked examples
- A reading of 5 hp converts to 3728499.358 mW.
5 hp × 745699.8716 = 3728499.358 mW - A value of 150 hp is 111854980.7 mW.
150 hp × 745699.8716 = 111854980.7 mW
Horsepower to Milliwatt conversion table
| Horsepower (hp) | Milliwatts (mW) |
|---|---|
| 0.25 hp | 186424.9679 mW |
| 0.5 hp | 372849.9358 mW |
| 1 hp | 745699.8716 mW |
| 1.5 hp | 1118549.807 mW |
| 2 hp | 1491399.743 mW |
| 5 hp | 3728499.358 mW |
| 10 hp | 7456998.716 mW |
| 25 hp | 18642496.79 mW |
| 50 hp | 37284993.58 mW |
| 100 hp | 74569987.16 mW |
| 150 hp | 111854980.7 mW |
| 200 hp | 149139974.3 mW |
| 300 hp | 223709961.5 mW |
| 400 hp | 298279948.6 mW |
| 500 hp | 372849935.8 mW |
| 1000 hp | 745699871.6 mW |
Where it's used
Horsepower are used for car and motorcycle engine power in the US and UK, while milliwatts appear in laser pointer and diode output. Both measure power (energy per unit time), so the conversion is a fixed factor.
Horsepower to other power units
| Conversion | 1 hp equals |
|---|---|
| horsepower to watt | 745.6998716 W |
| horsepower to milliwatt | 745699.8716 mW |
| horsepower to kilowatt | 0.7456998716 kW |
| horsepower to megawatt | 0.0007456998716 MW |
| horsepower to metric horsepower | 1.013869665 PS |
| horsepower to BTU per hour | 2544.433578 BTU/h |
| horsepower to refrigeration ton | 0.2120361315 TR |
| horsepower to kilocalorie per hour | 641.186476 kcal/h |
| horsepower to foot-pound per second | 550 ft·lbf/s |
Frequently asked questions
How many milliwatts are in 1 horsepower?
1 hp = 745699.8716 mW.
How do I convert horsepower to milliwatts?
Multiply the value in hp by 745699.8716. For example, 15 hp × 745699.8716 = 11185498.07 mW.
Is the hp to mW conversion exact?
Yes. Both units are defined exactly, so the ratio is exact; its decimal form does not terminate and is shown here to 10 significant figures (more with the precision selector).
Sources
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "horsepower (550 ft·lbf/s)".
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures , Table 7, SI prefixes.
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Convert Horsepower to Milliwatts. Retrieved October 17, 2026, from https://scientificconverters.com/power/horsepower-to-milliwatts/
IEEE
Scientific Converters, "Convert Horsepower to Milliwatts," scientificconverters.com. Accessed: Oct. 17, 2026. [Online]. Available: https://scientificconverters.com/power/horsepower-to-milliwatts/