Belt Length Calculator

Enter two pulley diameters and center distance to find belt length, speed ratio, and wrap angle.

Pulley 1 Diameter D1 (mm)

Pulley 2 Diameter D2 (mm)

Center Distance C (mm)

Driver Pulley RPM (Pulley 1)

Open Belt Length

Crossed Belt Length

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Speed Ratio

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Wrap Angle (small pulley)

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Driven RPM (Pulley 2)

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Belt Length Formulas

Open: L = 2C + π(D1+D2)/2 + (D1−D2)²/(4C)

Crossed: L = 2C + π(D1+D2)/2 + (D1+D2)²/(4C)

Speed Ratio = D1/D2

Wrap Angle = 180° − 2×sin⁻¹((D2−D1)/(2C))

Gear ratio.

Motor steps.

Rotational inertia.

Material stress.

Flow rate.

Convert units.