Belt Length Calculator
Calculate V-belt length from pulley diameters and center distance.
Enter dimensions for instant belt length calculation.
Enter pulley diameters and center distance — see belt length instantly.
Belt Calculation
V-belt length formula for two pulleys.
Formula: L = 2C + 1.57 x (D + d) + (D - d)squared / (4 x C)
Where:
- L = belt length
- C = center distance between pulleys
- D = large pulley diameter
- d = small pulley diameter
All measurements in the same units (inches or mm).
Speed ratio:
- Speed ratio = D / d
- Large pulley RPM = Small pulley RPM x (d / D)
Common belt cross-sections:
- A/4L: light duty (fans, pumps)
- B/5L: medium duty (HVAC, compressors)
- C: heavy duty (large industrial)
- D: very heavy duty
Tips:
- Measure old belt if possible for best accuracy.
- Belt numbers often include the length in inches (e.g., A68 = A-section, 68 inches).