Fareed Mohmed · Engineering
Motor & Gearbox Output Calculator
Motor · Reduction · Output
Set up a standard AC induction motor on the left — poles, frequency and power — and see its rated speed and torque. Pick a gearbox type and ratio on the right and see what comes out the other end.
Drivetrain Calculator
Motor speed and slip are typical figures for a standard 3-phase induction motor at rated load — actual nameplate values vary by manufacturer and frame size. Gearbox efficiencies are typical for a well-lubricated unit at rated load; confirm against the gearbox manufacturer's curve for a critical design.
AC Induction Motor
Gearbox Output
Explanatory Notes
Where rated motor speed comes from
An induction motor never quite reaches its synchronous speed (120 × frequency ÷ poles) under load — it "slips" behind the rotating magnetic field, and that slip is what produces torque. Smaller motors run at proportionally higher slip than larger ones; the typical full-load slip used here (5% under 5 kW, 3.5% from 5–37 kW, 2% above) is a rule-of-thumb, not a nameplate guarantee — always check the actual nameplate RPM for a real motor.
Torque scales with the ratio, minus losses
A gearbox trades speed for torque: output speed is motor speed divided by the ratio, and output torque is motor torque multiplied by the ratio — then reduced by the gearbox's mechanical efficiency, since some of that power is lost to friction and heat in the mesh.
Why worm gearboxes lose so much more than helical
Helical and planetary gears roll against each other with mostly rolling contact, so losses stay low (~2–4% per stage) regardless of ratio. A worm gear set meshes by sliding contact between the worm and wheel, and that sliding loss grows with the lead angle — which shrinks as the ratio increases. The result: a 5:1 worm box can be ~90% efficient, but a 100:1 worm box can drop to ~50%, wasting half the input power as heat. This is a real, well-documented trade-off, not a rounding error — it's why high-ratio drives are rarely built as a single worm stage in practice.
Use the output power check as a sanity test
Output power (from output torque and output speed) should come out to roughly input power × efficiency. If you're spec'ing a gearbox against a load, work backward from the required output torque and speed, then check the input power demand against the motor's rated power with some margin.
Related tools
For fastener sizing on motor or gearbox foot/flange bolts, see Bolt Grades — Axial, Shear & Torque. For choosing the mounting arrangement itself, see Motor & Gearbox Mount Selector.