Belt Drive Calculator — Pulley Speed, Torque & Belt Length | Engineering Calc Pro

⚙ Belt Drive Calculator

Speed ratio, RPM, torque, belt length & center distance

Driver Pulley Diameter (in)

Driven Pulley Diameter (in)

Driver Speed (RPM)

Center Distance (in)

Driver Torque (ft·lbf)

Drive Efficiency (%)

Speed Ratio

—

D₂/D₁

Driven Speed

—

RPM

Driven Torque

—

ft·lbf

Belt Length

—

Belt Speed

—

ft/min

Wrap Angle (driver)

—

Speed Ratio = D₂/D₁ | N₂ = N₁ × D₁/D₂

L = 2C + π(D₂+D₁)/2 + (D₂−D₁)²/(4C)

Wrap angle: θ = 180 − 60(D₂−D₁)/C

4 in driver at 1750 RPM drives a 10 in pulley, center distance 18 in, 30 ft·lbf input torque.

Ratio = 10/4 = 2.5 | N₂ = 1750/2.5 = 700 RPM

T₂ = 30 × 2.5 × 0.96 = 72 ft·lbf

Result: 700 RPM | 72 ft·lbf output torque