Conveyor Motor & Gearbox Sizing Calculator — Torque, HP, Gear Ratio

A conveyor drive is sized from the belt pull, not guessed from the belt width. Enter the running pull, the startup pull, and the belt speed — or send them straight from the belt pull calculator — and this card turns them into what the drive has to deliver: torque at the sprocket or drum, shaft speed, power at the belt, the motor size at your drive efficiency, and the gear ratio for the motor speed you plan to use. Give it the sprocket teeth and belt pitch, or a drum diameter, and it does the geometry.

Worked example: 500 lbf of sizing pull at 100 ft/min is 500 × 100 / 33,000 = 1.52 hp at the belt. At 85% drive efficiency the motor needs 1.78 hp, so the next standard size is 2 hp. On a 6 in pitch diameter the shaft turns 100 × 12 / (π × 6) = 63.7 rpm and carries 500 × 3 = 1,500 lb·in (169 N·m); a 1750 rpm motor needs a 27.5:1 reduction. The OneMotion auto-pick then lists every drum motor series at your belt width against the continuous and peak floors, and the manual entry checks a sprocket-driven shaft motor or a drum you already own, scenario by scenario, with an optional cool-ambient allowance.

Send to Drive Shaft carries the pull, torque, belt width, and pitch diameter into the shaft deflection and twist check.

How it works
  • Power at the belt (hp) = belt pull (lbf) × belt speed (ft/min) / 33,000; kW = hp × 0.746. The motor requirement is that power divided by the drive efficiency, rounded up to a catalog size.
  • Torque = belt pull × pitch radius; chordal pitch diameter = belt pitch / sin(180° / teeth). N·m = lb·in × 0.113.
  • Shaft rpm = belt speed × 12 / (π × pitch diameter); gear ratio = motor rpm / shaft rpm.
  • Drum motors are verdicted on the vendor belt-pull rating at the belt width, with the peak-to-continuous torque ratio for startup, because drum motors are derated below torque ÷ radius.
  • Worked example: 500 lbf at 100 ft/min → 1.52 hp at the belt, 1.78 hp at the motor, 2 hp standard; 6 in PD → 63.7 rpm, 1,500 lb·in, 27.5:1 from 1750 rpm.

Free, no login. Your inputs are saved in this browser. Values are engineering references — verify against manufacturer data and applicable codes before a final design.

Built by the engineers behind Sanitary belt conveyors.

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Questions engineers ask

How do I calculate conveyor motor horsepower?
Multiply the belt pull in pounds by the belt speed in feet per minute and divide by 33,000 for the power at the belt, then divide by the drive efficiency (about 0.85 for a gearmotor) and round up to a standard motor size. 500 lbf at 100 ft/min is 1.52 hp at the belt and a 2 hp motor.
How do I find the gear ratio for a conveyor?
Shaft rpm = belt speed × 12 / (π × sprocket pitch diameter). The ratio is the motor speed divided by that shaft speed: a 1750 rpm motor driving a 6 in pitch diameter at 100 ft/min needs 1750 / 63.7 ≈ 27.5:1.
Why is a drum motor rated in belt pull rather than torque?
A drum motor is a gearmotor inside a shell, and its usable pull is limited by heat and gearing rather than by torque ÷ radius. Vendors publish the belt pull at each tube length, so the auto-pick compares your sizing floors with that rating and applies the peak-to-continuous torque ratio for startup.
What is the difference between running pull, startup pull, and the sizing floor?
Running pull is the steady tension at the drive. Startup pull adds the static-friction ratio and the acceleration of the moving mass. The sizing floors are the running pull scaled by the wear scenario and the service factor, and the drive is verdicted on those, not on the bare running number.

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