Sizing Tools

The most common motor-sizing calculations — results update as you type.

Power · Torque · Speed

P (kW) = T (N·m) × n (rpm) / 9550

Solve for:

Power P

Torque T

N·m

Speed n

rpm

KV · Kt · Ke conversion

Kt = 9.549 / KV; Ke (V/krpm) = Kt × 104.72 = 1000 / KV

Torque constant Kt

N·m/A

Back-EMF constant Ke

V/krpm

Speed constant KV

rpm/V

Type in any field and the other two are converted. Applies to permanent-magnet DC, BLDC and servo motors.

Gearbox output

T₂ = T₁ × i × η; n₂ = n₁ / i

Motor torque

N·m

Motor speed

rpm

Ratio i

Efficiency

Output torque5.4N·m

Output speed300rpm

Output power170W

Stepper resolution & pulse rate

Pulses/rev = 360 / step angle × microsteps; f = v / lead × pulses/rev

Step angle

Microsteps

Screw lead

mm/rev

Target linear speed

mm/s

Pulses per revolution3,200pulse/rev

Resolution2.5µm/pulse

Required pulse frequency20,000Hz

Motor speed375rpm

Inertia matching

Reflected J' = J_L / i²; ratio = J' / J_M

Load inertia J_L

kg·cm²

Ratio i

Motor inertia J_M

kg·cm²

Load inertia reflected to motor shaft15kg·cm²

Inertia ratio14.3 : 1

High — lower the gains; response will be slower