How to calculate motor power, RPM and torque for a conveyor belt

thijs · September 2, 2026, 12:15am

Based on contributions by Okay.

Before you can choose a motor for a conveyor (or any similar drive application), you need to know the power, speed (RPM) and torque it must deliver. This walks through the three calculations with worked examples.

What you need

The conveyor’s belt speed target, or the length of the conveyor and how long an object should take to cross it
The mass of the heaviest object the conveyor needs to move
An estimate of the friction coefficient between the object and the belt (or between the belt and its rollers, depending on what’s driving the load)
The diameter of the drive roller

Steps

1. Determine the required belt speed

Divide the conveyor’s length by how many seconds you want an object to take to cross it.

Example: a 5-metre conveyor, with the object crossing it in 15 seconds:

v = 5 m / 15 s = 0.33 m/s

2. Calculate the required power

Power = Force × Velocity

Where Force is the frictional force resisting motion:

Force = μ × N = μ × m × g

m = mass of the object (kg)
g = gravitational acceleration, 9.81 m/s²
μ = friction coefficient (dimensionless)

Typical friction coefficients:

Situation	μ
Standard rubber conveyor belt on metal rollers	0.02 – 0.05
High-friction surfaces (textured or coated belts)	0.1 – 0.3
Low-friction applications (plastic belts, specialized coatings)	0.01 – 0.02

Once you have Force and Velocity, Power = Force × Velocity gives you the required power in watts (1 N·m/s = 1 W). Add a safety margin of 10–20% on top of the calculated value.

Check: the original notes for this calculation stated Power = Force / Velocity, which is dimensionally wrong (that would give N·s/m, not watts). The correct relation, used above, is Power = Force × Velocity.

3. Calculate the required RPM

You need the roller’s diameter and the target belt speed.

First, find the roller’s circumference:

circumference = diameter × π

Example: a roller with a 45 mm diameter:

circumference = 45 mm × π = 141.4 mm = 0.1414 m

Each roller revolution advances the belt by one circumference. So the number of revolutions needed per metre of belt travel is:

revolutions/metre = 1 / 0.1414 m ≈ 7.07 rev/m

Multiply this by the target belt speed (in metres per minute) to get the required RPM.

Example: for a target speed of 20 metres/minute with the 45 mm roller above:

RPM = 20 m/min × 7.07 rev/m ≈ 141.5 RPM

4. Calculate the required torque

Torque = Power (W) / Angular speed (rad/s)

Convert RPM to angular speed by multiplying by 2π/60.

Example: at 141.5 RPM:

Angular speed = 141.5 × 2π/60 ≈ 14.8 rad/s

Divide your calculated power by this angular speed to get the required torque in N·m. Use this torque (and the calculated RPM) to select a motor with matching or better specifications.