Mechanical calculator
Belt Length Calculator
Estimate the belt length for a two pulley open belt drive and check the resulting speed ratio.
What this calculation assumes
This is the standard approximate formula for an open belt connecting two pulleys on parallel shafts. It does not account for belt thickness, pulley groove geometry, tensioning travel, slip, or manufacturer specific pitch diameters.
Use the result as a selection starting point
- Choose a standard belt length that leaves room for tension adjustment.
- Use pitch diameter when the belt manufacturer provides it.
- Small pulleys may violate the belt’s minimum bend radius.
- Guards and alignment still matter after the math is correct.