Belt Calculator
Belt calculations depend on the job: open two-pulley length, V-belt center distance, timing-belt teeth, pulley speed ratio or belt tension. Start with the matching working calculator below.
Open belt length
For two parallel pulleys, the open-belt length is the two straight spans plus the wrap arcs, with a correction for different pulley diameters.
L = 2C + (pi/2)(D1 + D2) + (D2 - D1)^2 / (4C)
Choose the right belt tool
- Known center distance: use the belt length calculator.
- Known standard V-belt: use the V-belt calculator to solve center distance.
- Toothed belt: use the timing belt calculator for pitch length and teeth.
Grip and speed checks
After length is chosen, check small-pulley wrap, pulley ratio, belt speed and tension. A short belt that fits geometrically may still slip if wrap or tension is poor.
Frequently asked questions
Which belt calculator should I use?
Use belt length for two-pulley geometry, V-belt length when fitting a standard V-belt, and timing belt when tooth pitch and pulley tooth counts matter.
Should I use pulley outside diameter?
Use pitch or datum diameter for belt length. Outside diameter can overstate the pitch line, especially for V-belts.
Related pages
- Belt length calculator - open two-pulley belt length and wrap angle.
- V-belt length calculator - solve belt length from center distance or center distance from belt length.
- Timing belt calculator - pitch length, tooth count and pulley pitch diameters.
- Pulley calculator - pulley ratio, driven RPM and belt speed.
- Belt tension calculator - tight-side and slack-side tension from the capstan equation.