Belt Length Calculator (Fan Drives)
V-belt length from center distance and sheave sizes.
Enter your values
Enter the center distance in in.
Enter the small sheave diameter in in.
Enter the large sheave diameter 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 (pitch)
- 70.2 in
- Nearest standard (round to 0.1)
- 70.2 in
- Wrap angle small sheave
- 170.4 deg
Quick answer
Belt length is approximately twice the center distance plus the average sheave circumference correction plus a diameter-difference term.
L = 2C + pi(D1+D2)/2 + (D2-D1)^2/(4C)
At a glance
| What it does | V-belt length from center distance and sheave sizes. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Center distance, Small sheave diameter, Large sheave diameter |
| Main output | Belt length (pitch) |
| Formula | L = 2C + pi(D1+D2)/2 + (D2-D1)^2/(4C) |
| Cost | Free — no sign-up, no download |
How to use the Belt Length Calculator (Fan Drives)
- 1Measure or set the center distance between shafts.
- 2Enter the small and large sheave diameters.
- 3Order the nearest standard belt length to the calculated pitch length.
Inputs explained
- Center distance(in)
- Enter the center distance in in.
- Small sheave diameter(in)
- Enter the small sheave diameter in in.
- Large sheave diameter(in)
- Enter the large sheave diameter in in.
Worked example
Using the values the calculator loads with:
Inputs
- Center distance24 in
- Small sheave diameter5 in
- Large sheave diameter9 in
Results
- Belt length (pitch)70.2 in
- Nearest standard (round to 0.1)70.2 in
- Wrap angle small sheave170.4 deg
Frequently asked questions
Why is wrap angle shown?
Wrap angle below about 120 degrees on the small sheave reduces torque capacity and belt life.
What if sheaves are the same size?
The diameter-difference term drops out and length is simply 2C + pi x D.
What do I need to enter into the Belt Length Calculator (Fan Drives)?
Just 3 values: center distance, small sheave diameter, large sheave diameter. 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 (Fan Drives) work out the answer?
Belt length is approximately twice the center distance plus the average sheave circumference correction plus a diameter-difference term. It applies the formula L = 2C + pi(D1+D2)/2 + (D2-D1)^2/(4C) and shows the working so you can check each step by hand.
Is the Belt Length Calculator (Fan Drives) 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.