Simple machines — the lever, pulley, inclined plane, wheel-and-axle, and screw — all do the same basic job: they let you trade distance for force, so a smaller effort can move a larger load. This calculator computes the mechanical advantage (MA) for each of the five classic simple machines, the ideal effort force a given load requires, and how friction reduces that advantage in a real machine.
How the Mechanical Advantage Calculator works
Each simple machine has its own formula for ideal mechanical advantage (IMA), all derived from the same underlying principle: the ratio of two lengths (or a count, for pulleys). A lever compares effort-arm length to load-arm length; an inclined plane compares ramp length to height; a wheel-and-axle compares wheel radius to axle radius; a screw compares the circumference traced by the turning handle to the thread's pitch; and a pulley system's MA is simply the number of rope segments supporting the load.
Once the calculator knows the MA, it applies the universal relationship between load, effort, and mechanical advantage — Load = Effort × MA — to compute the effort force needed to move any given load, assuming an ideal, frictionless machine.
Inputs and what they mean
Machine-specific dimensions: each machine type asks for the lengths (or count) that determine its MA — see the Formula section above for exactly which ones. Getting these measurements right matters more than the load value, since MA is a pure ratio of dimensions.
Load (N): the force you're trying to overcome — the weight of an object, the resistance of a stuck bolt, or similar. If you only know a mass in kilograms, multiply by 9.8 m/s² to get newtons.
Efficiency (%): on the Efficiency tab, this represents how much of your input effort is lost to friction. Well-lubricated, well-built machines can exceed 90% efficiency; rough, high-friction setups (a rusty pulley, a dry-fit ramp) can drop well below 70%.
Limits and edge cases
This calculator computes ideal mechanical advantage from geometry alone; it does not model the physical mass or shape of the machine itself, only the ratios that determine leverage. For pulleys, it assumes the standard convention that MA equals the number of rope segments supporting the load — some pulley diagrams count differently depending on which segment you pull, so double-check against the diagram you're working from.
On the Efficiency tab, an efficiency of 0% has no meaningful actual mechanical advantage (the calculator will show no result) since a fully lossy machine wouldn't move the load at all in practice. Real machines with multiple simultaneous simple machines (e.g. a gear train combined with a lever) require multiplying each stage's MA together — this calculator handles one machine at a time.