Belt Length Calculator
V-belt length between two pulleys.
Enter your values
Enter the large pulley diameter in in.
Enter the small pulley diameter in in.
Enter the centre distance in in.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Belt length
- 58.49 in
- In millimetres
- 1486 mm
- Speed ratio
- 2.5:1
- Wrap angle (small)
- 160.8°
Quick answer
Belt length combines the wrap around both pulleys and twice the centre distance.
L = 2C + π(D+d)/2 + (D−d)²/(4C)
At a glance
| What it does | V-belt length between two pulleys. |
|---|---|
| Category | Engineering |
| Inputs needed | Large pulley diameter, Small pulley diameter, Centre distance |
| Main output | Belt length |
| Formula | L = 2C + π(D+d)/2 + (D−d)²/(4C) |
| Cost | Free — no sign-up, no download |
How to use the Belt Length Calculator
- 1Measure both pulley diameters.
- 2Measure the centre-to-centre distance.
- 3Order the nearest standard belt above the result.
Inputs explained
- Large pulley diameter(in)
- Enter the large pulley diameter in in.
- Small pulley diameter(in)
- Enter the small pulley diameter in in.
- Centre distance(in)
- Enter the centre distance in in.
Worked example
Using the values the calculator loads with:
Inputs
- Large pulley diameter10 in
- Small pulley diameter4 in
- Centre distance18 in
Results
- Belt length58.49 in
- In millimetres1486 mm
- Speed ratio2.5:1
- Wrap angle (small)160.8°
Frequently asked questions
Should I round up or down?
Round to the nearest standard size and use the tensioner for adjustment.
Does wrap angle matter?
Below 120° on the small pulley, belts start slipping.
What do I need to enter into the Belt Length Calculator?
Just 3 values: large pulley diameter, small pulley diameter, centre distance. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Belt Length Calculator work out the answer?
Belt length combines the wrap around both pulleys and twice the centre distance. It applies the formula L = 2C + π(D+d)/2 + (D−d)²/(4C) and shows the working so you can check each step by hand.
Is the Belt Length Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.