Belt Linear Speed CalculatorFree online other calculator — instant results, no sign-up
Calculate belt speed from pulley diameter and rotational speed.
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About the Belt Linear Speed Calculator
The Belt Linear Speed Calculator calculates the linear speed of a belt from a pulley's diameter in millimetres and rotational speed in revolutions per minute. It converts the distance travelled around the pulley each revolution into belt speed in metres per second, assuming no slip. With a pulley diameter of 100 mm and a pulley speed of 1000 rpm, the result is 5.235988 m/s.
- Pulley diameter (mm)
- The effective diameter of the pulley where the belt travels, measured in millimetres, with a default of 100 mm.
- Pulley speed (rpm)
- The pulley's rotational speed in revolutions per minute, with a default of 1000 rpm.
Formula and method
v = π × D × n / 60000; with the default inputs, v = π × 100 × 1000 / 60000 = 5.235988 m/s, rounded to six decimal places.
- vBelt linear speed in metres per second (m/s).
- DEffective pulley diameter in millimetres (mm).
- nPulley rotational speed in revolutions per minute (rpm).
- πPi, the ratio of a circle's circumference to its diameter.
Multiply the pulley diameter by π to obtain the circumference in millimetres per revolution. Multiply that circumference by the pulley speed to obtain millimetres per minute, then divide by 1000 to convert millimetres to metres and by 60 to convert minutes to seconds. The combined conversion divisor is 60000.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Pulley diameter100 mm
- Pulley speed1000 rpm
Results
- Result5.235988 m/s
How to use the Belt Linear Speed Calculator
- 1Identify the pulley's effective belt-running diameter, using the pitch diameter where specified by the belt or pulley manufacturer.
- 2Enter that value in Pulley diameter (mm); keep 100 for the default example.
- 3Enter the pulley's actual rotational speed in Pulley speed (rpm); keep 1000 for the default example.
- 4Run the calculation to convert pulley circumference and rotational speed into belt linear speed.
- 5Read the result in m/s; the default inputs produce 5.235988 m/s.
Reading your result
The Result row reports belt linear speed in metres per second, not pulley rotational speed. A result of 5.235988 m/s means the belt travels approximately 5.235988 metres along its path each second under the no-slip assumption. The six displayed decimal places represent numerical rounding, not guaranteed measurement accuracy.
Limitations
The calculation assumes a circular pulley, steady rotational speed, and no slip between the belt and pulley. Use the effective or pitch diameter appropriate to the belt system; the pulley outside diameter may not be the correct running diameter. Slip, belt stretch, loading, and speed fluctuations can cause actual belt speed to differ. This tool does not calculate belt tension, power capacity, or safe operating speed. Use a positive diameter and a nonnegative rotational speed when calculating speed magnitude.
Common questions
Should I enter the pulley's radius or diameter?+
Enter the diameter in millimetres, not the radius. For the default example, the diameter is 100 mm. Entering a radius in this field would underestimate belt speed by a factor of two.
Should I use outside diameter or pitch diameter?+
Use the effective diameter at which the belt travels. For toothed belts and many other belt-drive calculations, this is the manufacturer's pitch diameter rather than the outside diameter.
Can I use motor rpm as the pulley speed?+
Only if the pulley rotates at the same speed as the motor, such as when it is mounted directly on the motor shaft. If a gearbox or another drive stage lies between them, enter the pulley rpm after that speed change.
Does the result account for belt slip?+
No. The calculator equates belt speed with the pulley's circumferential speed. If the belt slips on the driving pulley, its actual speed can be lower than the calculated value.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
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Results are estimates for informational purposes and are not financial, medical or legal advice.