Mechanical horsepower.
Horsepowers to Milliwatts Converter — hp to mW
Convert Horsepower (hp) to Milliwatt (mW) using the exact conversion factor (1 horsepower = 745,699.8716 milliwatt). See the formula, worked examples, conversion table, history, and common uses.
Horsepowers to Milliwatts converter
Converter
Power Converter
Convert watts, horsepower, refrigeration tons, BTU per hour, and engineering power units.
Context values
Some unit families need one extra value for a physically accurate result.
Milliwatt is 0.001 watt units.
Result = input x 745.6998716 / 0.001.
Power uses the watt as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Horsepowers to Milliwatts
Horsepower and Milliwatt both describe power output, and the conversion is a routine part of comparing an engine or motor's spec sheet across countries that use different power units. Horsepower is most often used for us and uk vehicle engine power ratings.
Formula
milliwatts = horsepowers × 745699.871582
This factor comes from each unit's defined relationship to the category's base unit: 1 horsepower equals 745.699871582 base units, and 1 milliwatt equals 0.001 base units, so dividing one by the other gives the direct horsepower-to-milliwatt factor of 745699.871582.
Simple example
1 hp × 745699.8716 = 745,699.8716 mW
1 horsepower = 745,699.8716 milliwatts.
Real-world example
100 hp × 745699.8716 = 74,569,987.16 mW
100 horsepowers = 74,569,987.16 milliwatts.
Conversion table
| Horsepower (hp) | Milliwatt (mW) |
|---|---|
| 1 hp | 745,699.8716 mW |
| 10 hp | 7,456,998.716 mW |
| 100 hp | 74,569,987.16 mW |
| 500 hp | 372,849,935.8 mW |
| 1,000 hp | 745,699,871.6 mW |
| 5,000 hp | 3,728,499,358 mW |
Reverse conversion: Milliwatt to Horsepower
1 mW × 0.00000134102209 = 0.000001341 hp
1 milliwatt = 0.000001341 horsepowers.
horsepowers = milliwatts × 0.0000013410220896
For a page dedicated to this direction, see Milliwatt to Horsepower.
Understanding the Horsepower
Horsepower (hp) measures power. Mechanical horsepower is defined as exactly 745.6998715822702 watts. It is classified as a US/imperial customary unit.
Where it's used: United States and United Kingdom (vehicle and engine specifications)
Mechanical horsepower vs. metric horsepower. Mechanical horsepower (745.7 W) and metric horsepower/PS (735.5 W) differ by about 1.4% — a US car spec sheet in 'hp' and a European one in 'PS' are not directly comparable numbers without conversion.
Uses of the Horsepower today
- US and UK vehicle engine power ratings
- Motor and engine specifications in English-speaking markets
History of the Horsepower
James Watt popularized horsepower in the 1780s as a marketing figure, comparing his steam engines' output to the working capacity of a horse (based on his estimate of a horse turning a mill), so buyers could grasp engine capability in familiar terms. The unit stuck long after its origin as a sales tool, eventually being formally defined at exactly 550 foot-pounds per second.
Historical origin. Horsepower was not the invention of a single named person; it developed through the process described above.
Understanding the Milliwatt (mW)
Milliwatt is 0.001 watt units.
Horsepower — sources
- NIST Special Publication 811 — Documents the exact watt-equivalence of mechanical horsepower.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many milliwatts are in 1 horsepower?
1 horsepower equals 745,699.8716 milliwatts, using the exact defined conversion factor rather than an estimate.
How do I convert horsepower to milliwatt?
Multiply the horsepower value by 745699.8716. The converter above does this instantly to whatever precision you set.
How do I convert milliwatt back to horsepower?
Use the reverse factor: 1 milliwatt equals 0.000001341 horsepowers. You can also use the swap control in the converter above to flip the direction instantly.
What is a horsepower?
Horsepower (hp) measures power. Mechanical horsepower is defined as exactly 745.6998715822702 watts. It is classified as a US/imperial customary unit.
What is a milliwatt?
Milliwatt (mW) is a unit of power.
Is the horsepower to milliwatt conversion exact?
Yes. Mechanical horsepower is defined as exactly 745.6998715822702 watts. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
What is the difference between mechanical horsepower vs. metric horsepower?
Mechanical horsepower (745.7 W) and metric horsepower/PS (735.5 W) differ by about 1.4% — a US car spec sheet in 'hp' and a European one in 'PS' are not directly comparable numbers without conversion.
Where is the horsepower still used today?
United States and United Kingdom (vehicle and engine specifications)