Belt length calculator
Lost the old belt, or the code has worn off? Enter your pulleys and the distance between the shafts. We'll work out the belt size, then show you the closest belts we stock and exactly how much longer or shorter each one is.
Checking our stock…
Nearest sizes
| Belt | Length | vs your drive | Shaft centres |
|---|
Getting the measurements right
- Count the teethOn timing pulleys, the tooth count is more accurate than a diameter. Mark a tooth with a pen and count round.
- Measure the pitchMeasure from the centre of one tooth to the centre of the next. 8mm is the most common. Our how to measure guide shows you how.
- Check the shaft centresMeasure centre to centre with the motor in its normal running position, not slid all the way in or out.
Belt calculator questions
How do I work out the length of a timing belt?
Count the teeth on both pulleys, measure the shaft centres and choose the belt pitch. The calculator above converts the pulleys to pitch diameters and works out the belt length. Timing belts are made in whole numbers of teeth, so it then rounds to the nearest size and shows how far the shafts need to move to suit it.
What if the exact belt size isn't available?
Choose the nearest size your drive can take up. Most motors sit on slotted mounts or have a tensioner, so a belt a few millimetres longer or shorter will usually fit. The calculator shows how much the shaft centres would need to move for each size we stock. If that's more than your adjustment allows, call us and we'll source the exact length.
How do I measure the pitch of a timing belt?
Measure from the centre of one tooth to the centre of the next. For a more accurate reading, measure across ten teeth and divide by ten. 3mm, 5mm, 8mm and 14mm are the common metric pitches, and 8M is the one we sell most of. Our how to measure guide has diagrams.
Do V-belts and wedge belts use the same calculation?
The idea is the same, but V-belts are sized from the datum (pitch) diameter of the pulley, not the outside diameter. Wedge belts such as SPZ and SPA are sold by datum length. Classical belts such as A and B are usually sold by inside length, often in inches. The calculator handles both for you.
Still not sure?
Send us a photo of the drive with your measurements and we'll find the right belt for you.