How to use this calculator
- Enter transmitted power. Use the power carried by the chain after drivetrain efficiency or upstream losses are considered.
- Enter sprocket geometry. Enter driver sprocket teeth and chain pitch so speed and pitch diameter are derived from the chain layout.
- Enter driver speed. Use the RPM of the driver sprocket being checked.
- Apply service factor. Increase steady effective tension for starts, shock, duty cycle and uncertain loading.
- Compare the allowable. Enter the manufacturer allowable working tension per strand and the number of strands sharing the load.
How it works
A roller-chain sprocket advances one chain pitch for every tooth on each
revolution, so the average chain speed is:
v = p x z x n / 60000
with p in millimetres, z as driver teeth and
n in rpm.
Effective chain tension comes from steady power divided by chain speed: F = P / v The service-factor design tension is: Fd = F x SF The calculator then compares design tension with the allowable tension you enter for the selected chain and strand count.
The theoretical sprocket pitch diameter is also shown: PD = p / sin(pi / z) Use that geometry when you continue into the overhung load calculator or shaft checks. For sprocket ratio and driven RPM, use the sprocket calculator. For whole-link center-distance layout, use the chain length calculator.
Worked example
Verified against the live calculator
A single-strand ANSI #40-style chain has 12.7 mm pitch and a
15 tooth driver sprocket running at 1000 rpm.
Chain speed is 12.7 x 15 x 1000 / 60000 = 3.175 m/s.
At 5 kW, effective tension is
5000 / 3.175 = 1575 N. With service factor
1.5, design tension is 2362 N. If the entered
allowable tension is 8000 N per strand, utilization is
2362 / 8000 = 0.295. Average driver sprocket torque is
47.7 N*m.
Reference data
This calculator intentionally does not embed roller-chain rating tables. Chain ratings depend on chain series, strand arrangement, speed, lubrication, sprocket tooth count, duty cycle and manufacturer data.
| Quantity | Formula | Role |
|---|---|---|
| Average chain speed | v = p x z x n / 60000 | Pitch times teeth per revolution, converted to m/s. |
| Effective tension | F = P / v | Steady power-transfer chain pull. |
| Design tension | Fd = F x SF | Service-factor tension for sizing comparison. |
| Pitch diameter | PD = p / sin(pi / z) | Theoretical roller pitch circle for layout and shaft-load context. |
| Average torque | T = P / omega | Shaft torque at the driver sprocket. |
| Utilization | U = Fd / (Fallow x strands) | Design tension compared with entered allowable tension. |
Source: Standard roller-chain drive geometry and steady power-transfer relations. Use manufacturer horsepower and working-load ratings for final chain selection.
Frequently asked questions
How do you calculate roller chain tension from horsepower?
Convert horsepower or kW to transmitted power, calculate average chain speed from pitch, teeth and RPM, then divide power by chain speed: F = P / v.
How do you calculate roller chain speed?
Average chain speed is v = p x z x n / 60000 when pitch p is in millimetres, z is driver sprocket teeth and n is RPM. In one revolution, the sprocket advances one chain pitch per tooth.
Is design tension the same as effective tension?
No. Effective tension is the steady power-transfer force. Design tension multiplies it by the service factor for shock, starts, duty cycle and uncertainty.
Can this pick the correct roller chain size?
No. It compares against the allowable tension you enter. Final chain selection still depends on manufacturer horsepower tables, speed limits, lubrication, sprocket tooth count, wear life and duty.
Why is sprocket pitch diameter included?
Pitch diameter is useful for shaft and overhung-load checks. This page derives the theoretical pitch diameter with PD = p/sin(pi/z), but tension is calculated from average chain speed.
Method & assumptions
- Steady average power-transfer tension only; starting shock and impact are represented only by the entered service factor.
- Average chain speed uses pitch times teeth per revolution; real chain motion has polygonal speed variation on the sprocket.
- Allowable tension must come from the selected chain manufacturer and application basis.
- Centrifugal tension, chain sag, installation tension, lubrication, wear, temperature, sprocket tooth capacity and shaft/bearing reactions are not included.
- Final selection needs manufacturer horsepower tables, speed limits, chain wrap, alignment, tensioner guidance and maintenance requirements.