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Drive Ratio, Speed & Torque Calculator

Pulley and gearbox ratio, output speed, shaft torque and drum surface speed.

Metric · IS practiceFormula shown with your numbersNothing stored

How this calculator works

Total reduction is the pulley ratio multiplied by the gearbox ratio. Output speed is motor speed divided by that total. Torque at the output shaft comes from power and speed directly. For a conveyor, the drum surface speed follows from the output rpm and the drum diameter, which is the number you actually check against the belt speed you wanted.

Formulas used

Pulley ratioi_p = D_driven ÷ D_driver
Total reductioni = i_p × i_gearbox
Output speedn_out = n_motor ÷ i (rpm)
Shaft torqueT = 9550 × kW ÷ rpm (N·m)
Drum surface speedv = π × D_drum × n_out ÷ 60000 (m/s)

Checked against

3.7 kW through a 50:1 reduction from 1440 rpm gives 28.8 rpm and 1104 N·m at the output shaft.

Worth knowing

Torque shown is the steady running value. Size couplings, keys and shafts on the starting torque, which for a direct-on-line motor can be two to three times the running figure.

Drive Ratio, Speed & Torque Calculator — common questions

How do I calculate torque from kW and rpm?
T = 9550 × kW ÷ rpm, giving newton-metres. 3.7 kW at 28.8 rpm is 9550 × 3.7 ÷ 28.8 = 1227 N·m before gearbox losses.
How do I set conveyor belt speed with a gearbox?
Work backwards. Belt speed and drum diameter give you the drum rpm you need, motor speed divided by that rpm gives the total reduction, and you split it between the gearbox and the pulley pair.

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Contact

Chennai, Tamil Nadu

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+91 91763 23669

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Eshwar C S

Works & office

T-231 A, Sidco Women's Industrial Park
Kattur, Avadi, Chennai – 600 062
Tamil Nadu, India

GSTIN

33DENPP4793D1Z5

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Sidco Women’s Industrial Park, Kattur · Avadi, Chennai

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