How to use this calculator
- Enter transmitted power. Use the mechanical power carried by the chain.
- Enter sprocket pitch diameter. Use pitch diameter, not outside diameter.
- Enter RPM. Use the speed of the sprocket being checked.
- Apply service factor. Increase pull for shock, starts, duty cycle and uncertain loading.
- Compare allowable load. Use the selected chain manufacturer rating for the utilization check.
How it works
Chain speed at the sprocket pitch line is:
v = pi x D x n / 60
with D in metres and n in rpm.
Effective chain pull is F = P / v. The design pull multiplies this
by the service factor. Sprocket torque follows from the pitch radius:
T = F x D / 2. To see how that sprocket force loads the shaft
bearings, use the overhung load calculator.
Worked example
Verified against the live calculator
A chain transmitting 5 kW on a 100 mm pitch-diameter
sprocket at 300 rpm has speed 1.571 m/s.
Effective pull is 5000 / 1.571 = 3183 N. With service factor
1.5, design pull is 4775 N. The sprocket torque is
159.2 N*m.
Frequently asked questions
How do you calculate chain pull from power?
Effective chain pull is transmitted power divided by chain pitch-line speed: F = P / v. The pitch-line speed is v = pi*D*n/60 using sprocket pitch diameter D and RPM n.
How do you calculate sprocket torque from chain pull?
Torque is chain pull times pitch radius: T = F * D / 2, where D is the sprocket pitch diameter.
What is design chain pull?
Design chain pull is effective pull multiplied by a service factor for shock, duty cycle and uncertain loading. Compare it with the manufacturer allowable working load.
Does this include chain sag or centrifugal force?
No. It is a steady power-transfer check. Sag, installation tension, centrifugal pull, impact, lubrication and wear need separate manufacturer guidance.
Can I use this for timing belts?
The power-over-speed relation is the same, but belt tooth capacity and pretension are different. Use it only as a pitch-line force estimate.
Does it work in imperial units?
Yes. Toggle units to display horsepower, inches, lbf, ft/min and lbf*ft while the internal calculation remains unit safe.
Method & assumptions
- Steady power-transfer calculation:
F = P / v. - Sprocket speed uses pitch diameter, not outside diameter.
- Design pull is a simple service-factor multiplication.
- Starting shock, impact, sag, centrifugal pull, lubrication, wear, sprocket tooth capacity and chain selection tables are not included.