What is mechanical horsepower?
A unit of power equal to 745.7 watts, often used for engines and shafts.
Horsepower Calculator
Find mechanical or electrical horsepower, or convert between horsepower and watts.
Calculate horsepower
Pick a mode, then enter torque & RPM, electrical inputs, or a power value to convert.
About this calculator
How to use Horsepower Calculator, plus the formulas and logic behind the results.
Tool description
The Horsepower Calculator covers mechanical shaft power, approximate electrical input-to-HP conversion, and simple HP↔watt conversions.
How to use
- Select mechanical, electrical, or convert mode.
- Enter the values described by that mode.
- Select Calculate to view HP and watt equivalents.
Formulas & reference
HP_mech = (τ × RPM) ÷ 5252P_W_single = V × I × PF × (η ÷ 100)P_W_three = √3 × V × I × PF × (η ÷ 100)HP = P_W ÷ 745.7
Power identities
- Mechanical HP = (τ_lbft × RPM) ÷ 5252
- 1 mechanical HP = 745.7 W
- Single-phase W ≈ V × I × PF × η
- Three-phase W ≈ √3 × V × I × PF × η
Calculation logic
Mechanical mode uses the 5252 constant for lb·ft and RPM. Electrical mode builds watts from V/I/PF/efficiency (with √3 for three-phase), then divides by 745.7. Convert mode applies the same HP↔watt factor.
Electrical mode uses line voltage and assumes the efficiency/PF you enter. Motor nameplates may define HP differently for intermittent duty.
Horsepower Calculator FAQ
Common questions about this calculator and how to use the results.
What torque units are required?
Use pound-feet (lb·ft) in mechanical mode.
Why include efficiency and PF?
They reduce ideal VI power to a more realistic electrical input estimate.
Is metric PS the same as HP?
Metric horsepower (PS) is about 735.5 W—close but not identical to 745.7 W mechanical HP.
Can RPM be zero?
No. Mechanical mode needs RPM greater than zero.
Does this size a motor?
It estimates power. Always confirm with manufacturer data and duty cycle.