How do I calculate the correct timing belt width for my drive?
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- Issue Time
- Oct 16,2026
Short answer: width is sized from the torque (or power) the belt must transmit and the speed of the drive. Start from the design power (transmitted power × service factor), read the belt rating per unit width for your pitch and speed, then divide to get the minimum width — and round up to the nearest standard width. When in doubt between two widths, choose the wider one.
The sizing logic in four steps
1. Design power
Multiply the transmitted power by a service factor (commonly about 1.1–1.6 depending on load type, starting frequency and duty hours).
2. Belt speed
Belt speed = pitch diameter × RPM. Higher speed usually means higher per-width capacity, but check the pitch limit for your profile.
3. Per-width rating
Manufacturer tables give torque or power per 10 mm (or per inch) of width for each pitch and speed. Interpolate if your speed falls between rows.
4. Round up
Required width = design power ÷ per-width rating. Round up to a standard stock width rather than rounding down.
Practical rules of thumb
- Higher shock loads or frequent starts → apply a larger service factor rather than guessing.
- Small pulley diameter reduces tooth engagement — if the small pulley has fewer teeth than recommended for the pitch, step up one width class.
- Idlers on the back or inside of the belt add bending stress; allow extra width margin when they are present.
- For conveyor or positioning duty with constant load, width can often stay at the minimum rating; for reciprocating loads, add margin.
What data we need from you
| Parameter | Why it matters |
|---|---|
| Motor power and RPM | Determines torque and belt speed |
| Pitch and tooth profile | Must match existing or new pulleys |
| Pulley teeth / diameters | Affects tooth engagement and capacity |
| Center distance | Determines belt length |
| Load type and duty hours | Sets the service factor |
Undersized belts wear teeth and jump; oversized belts raise bearing loads and cost. A short check of the drive data usually pays for itself. Values above are industry-general guidance — final sizing depends on your actual drive.
Send us your drive data
Share motor power, RPM, pulley sizes and load type — we will size the pitch and width for you and quote standard or custom belts.
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