BALKE WORKBENCH / MAKER & MOTION

Pulley & belt calculator.

Calculate pulley ratios, belt speed, pitch length, and center distance for an open two-pulley drive.

Local calculations · live results

Pitch geometry

Solve forPulley dimensionsLength unitsCommon belt pitchBelt pitch (mm)Driver pulley teethDriven pulley teethCenter distance (mm)Driver RPM · optionalLeave blank to omit speed calculations. 0 means stationary.

Use pitch diameters and pitch length. Outside pulley diameter and outside belt circumference are not interchangeable with pitch dimensions. Pitch alone does not establish matching tooth profiles.

BELT PITCH LENGTH

240 mm

Driver Ø 12.7324 mm · driven Ø 12.7324 mm
C = 100 mm · L = 240 mm
20T → 20T · pitch 2 mm · same rotation direction

Schematic · not to scale

Driver pitch diameter: 12.7324 mm
Driven pitch diameter: 12.7324 mm
Reduction · driver RPM / driven RPM: 1:1
Pitch length: 240 mm
Center distance: 100 mm
Wrap on smaller pulley: 180 °
Driven speed: 300 RPM
Belt speed: 200 mm/s
Theoretical belt tooth count: 120

Choose a whole-tooth belt

A fractional tooth count is theoretical, not a purchasable belt. Choose an integer count to recalculate center distance. Integer counts do not establish catalog availability.

Selected belt teeth

Selected 120 teeth: 240 mm pitch length → 100 mm center distance.

Formulas & assumptions

Timing pitch diameter = teeth × pitch / π Driven RPM = driver RPM × driver diameter / driven diameter Belt speed = π × driver pitch diameter × RPM / 60 Δ = |D₂ − D₁| / 2; α = asin(Δ / C) L = 2√(C² − Δ²) + π(D₁ + D₂)/2 + 2Δα Small-pulley wrap = π − 2α (radians)

The exact tangent-and-arc geometry is applied at the belt pitch line. Center distance is solved by 100 bounded bisection steps. The model requires C > (D₁ + D₂)/2, so pitch circles neither overlap nor touch. Real outside dimensions and installation clearances still need checking.

Open, two-pulley drive only: no crossed belts, idlers, tensioners, stretch, or slip. Geometric fit does not establish suitable belt width, tension, load capacity, or minimum tooth engagement.

Engineering references:

Calculation summary

Pulley & Belt Calculator
Mode: timing; solve: belt pitch length; units: mm
Belt pitch: 2 mm; driver: 20 teeth; driven: 20 teeth
Driver speed: 300 RPM
Driver pitch diameter: 12.7324 mm
Driven pitch diameter: 12.7324 mm
Reduction · driver RPM / driven RPM: 1:1
Pitch length: 240 mm
Center distance: 100 mm
Wrap on smaller pulley: 180 °
Driven speed: 300 RPM
Belt speed: 200 mm/s
Theoretical belt tooth count: 120
Exact ideal open-belt geometry on pitch circles. No crossed belts, idlers, tensioners, stretch, or slip. Fractional teeth are theoretical only; integer teeth do not establish catalog availability. Fit does not establish width, tension, load capacity, or minimum tooth engagement.