This mechanical advantage of a screw calculator finds the ideal mechanical advantage (IMA) — how much a screw multiplies your effort. Enter the effort arm length and the thread pitch above to get the IMA.
How is it calculated?
IMA = (2 × π × L) ÷ P
- L — length of the effort arm (handle or wrench radius)
- P — pitch (lead): distance advanced per full turn
The numerator is the circular distance your hand travels in one turn; the pitch is how far the screw moves in that same turn.
Example calculation
For an effort arm L = 10 in and pitch P = 0.1 in:
- IMA = (2 × π × 10) ÷ 0.1 = 628
So the screw ideally multiplies your force about 628 times, before friction losses.
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Frequently Asked Questions
How do you calculate the mechanical advantage of a screw?
Divide the circumference of the effort (2 times pi times the handle length) by the screw’s pitch, or lead. A longer handle and finer pitch give more advantage.
What is the pitch of a screw?
The pitch is the distance the screw advances in one full turn. A smaller pitch means finer threads and a higher mechanical advantage.
Is this ideal or actual mechanical advantage?
It is the ideal mechanical advantage, which ignores friction. Real screws lose much of it to friction, but IMA is the standard design figure.