By Zencalcy Editorial TeamLast reviewed About us
A screw converts a small torque applied over many turns into a large linear force. Its ideal mechanical advantage is the distance the effort travels in one turn, 2πR, divided by the pitch — the distance the screw advances in that turn.
Force multiplication from handle radius and thread pitch.
MA = 2π R / p F_load = F_effort × MA
R is the effort radius in metres and p is the pitch in metres per revolution. Real screws lose much of this advantage to thread friction, so actual MA is far lower.
| Symbol | Meaning |
|---|---|
| MA | Ideal mechanical advantage, dimensionless. |
| R | Effort radius, in metres. |
| p | Thread pitch, in metres per turn. |
MA = 2π × 0.02 / 0.002 = 62.8, so 100 N of effort could in theory generate 6,283 N. Friction typically cuts the real figure to a small fraction of that.
Continue with the Wedge Mechanical Advantage Calculator, Wheel and Axle Calculator, or the Gear Ratio Calculator — or browse more simple machines tools and all physics calculators.
Thread friction consumes most of the input work, especially in shallow threads. Lubrication and thread form matter more than the geometric ratio.
Results are computed from the standard equations of classical mechanics. Unit conversions use the SI definitions published by NIST. Air resistance is ignored unless the calculator names a drag model.
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Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026