Worm Gear Calculator

Inputs

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Number of starts (threads) on the worm. 1 gives the highest reduction.
Number of teeth on the worm wheel.
Axial module of the worm.
mm
Pitch diameter of the worm.
mm

Results

Default result
Edit inputs
Gear ratio(i)
40
Pass

40:1 reduction.

Z₂ ÷ Z₁ (n:1).

Also computed

Wheel pitch diameter(d₂)80mm

Center distance(a)50mm

Lead(L)6.283mm

Axial advance per worm revolution.

Lead angle(λ)Caution5.711°

Likely self-locking — cannot be back-driven.

Method notes 3 notes
  • Ratio i = wheel teeth ÷ worm starts; a single-start worm gives a ratio equal to the wheel tooth count.
  • Lead L = Z₁ · π · m is the axial advance per worm revolution; lead angle λ = atan(L / (π · d₁)).
  • A worm set is likely self-locking when λ ≲ 5–6° (below the friction angle) — a guide, not a guarantee. Efficiency falls as the lead angle drops.

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