Should I use motor speed or measured pulley speed?

Use motor-shaft RPM with the actual reduction ratio. If you know pulley RPM instead, enter it in the motor-shaft-speed field and set the ratio to 1. Belt slip is a separate correction; keep it at 0 unless known.

What belt slip value should I use?

There is no reliable universal slip percentage. Leave it at 0 for theoretical speed, or enter a measured value. Motor nameplate RPM already reflects the motor’s operating speed and is not this slip input.

Does this account for belt thickness?

Only through the diameter you enter. The running or pitch diameter can differ from the bare pulley diameter depending on belt construction and lagging. Verify the effective diameter or measure belt speed if precision matters.

Can I use this for a multi-pulley drive?

The formula gives the speed at the drive pulley. On a multi-pulley drive, speed is the same everywhere on the belt unless there is measurable slip at a specific pulley, so the result still holds — but local slip differs and this tool cannot resolve that.

Why does the output show three units?

Because the units people use depend on the trade: m/s in engineering documents, ft/min on conveyor specification sheets in North America, ft/s in some bulk-handling contexts. Showing all three avoids a conversion mistake downstream.

Free tool

Belt Speed Calculator

Work out conveyor belt speed from pulley diameter and motor RPM, in m/s, ft/min and ft/s — with the formula, the slip correction and a worked example shown alongside the result.

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Formula shown
updated 2026-09

Calculate

Enter your values

Results update as you type. Everything is computed in the browser.

Drive-pulley diameter (mm)

Effective running diameter, including lagging.

Motor shaft speed (rpm)

Use actual motor-shaft RPM if available; nameplate RPM is an estimate.

Gear ratio (:1)

Enter 1 if the pulley is directly driven.

Belt-to-pulley slip (%)

Leave at 0 unless measured or specified; this is not motor slip.

Result

Belt speed (m/s): 0.949
Belt speed (ft/min): 186.8
Belt speed (ft/s): 3.11
Pulley speed (rpm): 72.5

Computed in your browser. Inputs are not sent to a server.

Method

The formula, and every assumption behind it

A number you cannot check is not usable in engineering or finance work. This is the whole calculation.

v = (π × D × n) / 60

With gearbox and measured belt slip: n_pulley = n_motor / ratio; v = π × D × n_pulley / 60 × (1 − slip/100).

Variables

Variables used by the Belt Speed Calculator
Symbol	Meaning	Unit
v	Belt speed	m/s
D	Pulley diameter (converted to metres)	m
n	Pulley rotational speed	rpm
n_motor	Motor-shaft speed	rpm
ratio	Gearbox reduction ratio	:1
slip	Belt-to-pulley slip	%

Assumptions and limits

Steady-state running; acceleration and starting torque are out of scope.
The entered diameter is the effective running diameter. Belt thickness and lagging can change it; check the relevant pitch line for your belt.
Belt-to-pulley slip is optional and applied once at the drive. Do not confuse it with motor slip already reflected in actual motor RPM.
This estimates speed at one drive pulley, not local speed or slip in a multi-pulley drive.

Further reference:Forbo conveyor calculation methods

How to use it

Five steps

01
Enter the effective running diameter of the drive pulley, including lagging.
02
Enter motor-shaft RPM before the gearbox. Measured RPM is best; nameplate RPM is an estimate.
03
Enter the gearbox ratio. For a direct drive, enter 1.
04
Keep belt-to-pulley slip at 0 unless a measured or specified value is available.
05
Read the result in m/s for engineering work or ft/min for a specification sheet.

Worked example

Worked example — 250 mm pulley, 1450 rpm motor, 20:1 gearbox, 1% slip

The example shows the inputs and main steps so you can check the result.

Inputs

Pulley diameter: 250 mm
Motor speed: 1450 rpm
Gear ratio: 20:1
Slip: 1%

Worked example, step by step
Step	Value
Pulley speed	1450 / 20 = 72.5 rpm
Pulley circumference	π × 0.250 m = 0.7854 m
Theoretical belt speed	0.7854 × 72.5 / 60 = 0.949 m/s
Slip correction	× (1 − 0.01) = 0.9395 m/s
Belt speed (m/s)	0.94 m/s
Belt speed (ft/min)	0.9395 × 196.8504 = 184.9 ft/min

Units

Useful unit conversions

Shown so you can reconcile the output with the units in your own data.

Unit conversions
Metric	Equivalent
1 m/s	196.85 ft/min
1 m/s	3.281 ft/s
1 ft/min	0.00508 m/s
1 mm diameter	0.03937 in
1 rpm	1 rpm (no conversion)

Questions

Common questions

Should I use motor speed or measured pulley speed?: Use motor-shaft RPM with the actual reduction ratio. If you know pulley RPM instead, enter it in the motor-shaft-speed field and set the ratio to 1. Belt slip is a separate correction; keep it at 0 unless known.
What belt slip value should I use?: There is no reliable universal slip percentage. Leave it at 0 for theoretical speed, or enter a measured value. Motor nameplate RPM already reflects the motor’s operating speed and is not this slip input.
Does this account for belt thickness?: Only through the diameter you enter. The running or pitch diameter can differ from the bare pulley diameter depending on belt construction and lagging. Verify the effective diameter or measure belt speed if precision matters.
Can I use this for a multi-pulley drive?: The formula gives the speed at the drive pulley. On a multi-pulley drive, speed is the same everywhere on the belt unless there is measurable slip at a specific pulley, so the result still holds — but local slip differs and this tool cannot resolve that.
Why does the output show three units?: Because the units people use depend on the trade: m/s in engineering documents, ft/min on conveyor specification sheets in North America, ft/s in some bulk-handling contexts. Showing all three avoids a conversion mistake downstream.

Understand the method

Check the calculation before you use the result

The guide explains which diameter and RPM belong in the formula, how a gearbox changes the input and when field measurement matters.

9 min guide

How to Calculate Conveyor Belt Speed

Calculate theoretical conveyor belt speed from drive-pulley diameter and pulley RPM, then account for gearbox ratio, effective diameter and measured slip.

Understand the method

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