Search this site

Try a part name, a rupee figure, or the fault you are chasing.

Free project pack

Wheel speed and RPM calculator for robots

Robot speed is wheel circumference times wheel turns per second. Enter the wheel diameter and either the RPM or the speed you want.

From RPM: – m/s (– km/h)For the target speed, wheel RPM needed: –

Real speed is lower than this under load, and the tyre squashes a little, which changes the effective diameter.

How it is calculated

Circumference = π × diameter. Speed in m/s = circumference in metres × RPM ÷ 60. Needed RPM = speed × 60 ÷ circumference. Multiply m/s by 3.6 for km/h.

A worked example

A 65 mm wheel has a circumference of π × 0.065 = 0.204 m. At 150 RPM it moves 0.204 × 150 ÷ 60 = 0.511 m/s, about 1.84 km/h. To drive at 0.5 m/s you need 0.5 × 60 ÷ 0.204 = 147 RPM.

Common mistakes

  • Typing the radius where the diameter is asked for.
  • Using motor RPM instead of wheel RPM. Divide by the gear ratio first.
  • Ignoring that two-wheel robots turn by running the wheels at different speeds.

gear train calculator, battery runtime calculator, robot under ₹2,000.

Last reviewed: November 2026. The calculator runs in your browser and sends nothing anywhere. Results are ideal-case figures; add margin before you order parts.

Another worked example

A 100 mm wheel has a circumference of π × 0.1 = 0.3142 m. At 60 RPM it moves 0.3142 × 60 ÷ 60 = 0.314 m/s, which is 0.314 × 3.6 = 1.13 km/h. To drive at 0.3 m/s you need 0.3 × 60 ÷ 0.3142 = 57.3 RPM.

Turning with two driven wheels

A differential-drive robot turns because its two wheels run at different speeds. If the distance between the wheel contact points (the track width) is b, the turning rate is (right speed − left speed) ÷ b in radians per second. With a track of 150 mm, a right wheel at 0.4 m/s and a left wheel at 0.2 m/s: 0.2 ÷ 0.15 = 1.333 rad/s, which is about 76 degrees per second. The robot’s forward speed is the average of the two wheels, 0.3 m/s.

From motor to wheel

Motor datasheets list shaft RPM. If a gearbox sits between the motor and the wheel, divide the motor RPM by the gear ratio first. A motor at 3,000 RPM through a 30:1 gearbox gives a wheel at 100 RPM.

Assumptions and limits

  • No-load RPM is a maximum. Under load and at battery voltage that sags, the real speed is lower.
  • Wheels slip, especially while accelerating. Use encoders if you need distance that is more accurate than a calculation.
  • Soft tyres squash and change the effective rolling diameter. Measure it by rolling the wheel over a marked distance if it matters.

Common mistakes

  • Entering the diameter in centimetres into a millimetre field.
  • Forgetting that a different wheel size changes both top speed and the torque available at the ground.