Calculating Belt Speed on Your 2x72 Grinder

Belt speed depends on drive-wheel diameter and actual motor RPM. Use the wheel diameter—not its radius or bore size.

Calculate Surface Feet per Minute (SFM)

SFM = π × drive-wheel diameter in inches × RPM ÷ 12

π is approximately 3.1416. The wheel travels one circumference (π × diameter) per revolution.

Example: 5-inch wheel at 3,450 RPM

3.1416 × 5 × 3,450 ÷ 12 ≈ 4,516 SFM.

Convert between SFM and MPH

MPH = SFM ÷ 88
SFM = MPH × 88

4,516 SFM is approximately 51.3 MPH. A belt speed of 14 MPH is 1,232 SFM.

Use our Belt Speed Calculator to compare setups. A calculated speed does not establish a safe operating limit: follow the ratings and instructions for the belt, wheels, attachments and motor/VFD.