Motor Torque Calculator
Find a motor's output torque from its rated power and shaft speed — in N·m from kW and RPM, or lb-ft from HP and RPM.
Enter your values
Motor rated power and shaft speed.
How this calculator works
Motor output torque relates to power and rotational speed through the basic power-torque relationship, P = T·ω, rearranged for torque:
For horsepower input, the equivalent constant is 5252 for torque in lb-ft: T (lb-ft) = 5252 × P (HP) / N (rpm). Both forms come from converting power and angular speed into consistent units.
Common motor speeds (4-pole, 50/60 Hz)
| Supply frequency | Synchronous speed | Typical full-load speed |
|---|---|---|
| 50 Hz | 1500 rpm | ~1440–1470 rpm |
| 60 Hz | 1800 rpm | ~1740–1770 rpm |
Full-load speed is slightly below synchronous speed due to slip in induction motors — use the nameplate rated speed for accurate torque figures.
Frequently asked questions
Should I use nameplate power or actual load power?
For rated (full-load) torque, use the nameplate rated power and rated speed. For torque at a specific operating point, use the actual power draw and speed at that point instead.
How is this different from the Motor Power Calculator?
The Motor Power Calculator sizes the power needed for a known torque and speed demand; this calculator works the other way — from a motor's rated power, back to its output torque.