Mechanical Advantage Calculator
Ideal and actual mechanical advantage of a lever, pulley system, wheel and axle, inclined plane or screw, and the effort needed to move a load.
Result…
How it's calculated
Lever: MA = effort arm ÷ load arm Pulley: MA = number of supporting rope segments Wheel and axle: MA = wheel radius ÷ axle radius Inclined plane: MA = slope length ÷ height Screw: MA = 2π × handle radius ÷ lead Actual MA = ideal MA × efficiency; effort = load ÷ MA
Mechanical advantage is the ratio of the load a machine moves to the effort you apply. For an ideal machine it equals the ratio of distances: how far the effort moves for each unit the load moves. Each simple machine has its own distance ratio, listed in the formula. Real machines lose some effort to friction, so the actual mechanical advantage is the ideal one times the efficiency. Lengths only need to share a unit because the ratio has none; force units are converted with exact factors (1 lbf = 4.4482216152605 N, 1 kgf = 9.80665 N).
Your numbers, step by step
About the Mechanical Advantage calculator
This mechanical advantage calculator works out how much a simple machine multiplies your force. Choose a lever (class 1, 2 or 3), a pulley system, a wheel and axle, an inclined plane or a screw, enter its dimensions, and it gives the ideal mechanical advantage from the distance ratio. Add the load and the machine's efficiency to see the actual mechanical advantage and the effort you really need, in N, kN, lbf or kgf. Lengths can be in mm, cm, m, inches or feet, as long as both share a unit. It is handy for physics and technology lessons, for planning a block and tackle, a ramp for a wheelbarrow or a car jack, and for checking whether a lever is long enough. The working is shown step by step, so you can follow each ratio.
How to use it
- Pick the “Simple machine”, and for a lever choose the “Lever class”.
- Enter its dimensions, such as “Effort arm” and “Load arm”, or the “Rope segments supporting the load”.
- Enter the “Load” and pick the “Force unit”.
- Set “Efficiency” to 100 for an ideal machine, or lower for friction.
- Read the ideal and actual mechanical advantage and the effort needed.
Worked example
A block and tackle has 4 rope segments holding a 1200 N load. The ideal mechanical advantage is 4, so an ideal pull would be 1200 ÷ 4 = 300 N. At 75% efficiency the actual mechanical advantage is 4 × 0.75 = 3, and the real pull is 1200 ÷ 3 = 400 N. You still pull 4 m of rope for every 1 m the load rises.
Updated
Questions people ask
How do I calculate mechanical advantage?
Divide the distance the effort moves by the distance the load moves. For a lever that is the effort arm ÷ the load arm; for a pulley it is the number of rope segments holding the load.
What is the difference between ideal and actual mechanical advantage?
Ideal mechanical advantage comes from the geometry alone. Actual mechanical advantage is load ÷ real effort, which is lower because of friction; it equals the ideal value times the efficiency.
What are the three classes of lever?
A class 1 lever has the pivot between effort and load, like a seesaw. Class 2 has the load in the middle, like a wheelbarrow, so its advantage is always above 1. Class 3 has the effort in the middle, like tweezers, so its advantage is below 1 but the load moves further and faster.
How do I count rope segments in a pulley system?
Count the rope sections that hold up the moving pulley block. A common mistake is to count the free end you pull down on, which adds nothing unless it pulls upward from the moving block.
Is a mechanical advantage calculator safe for rigging and lifting?
It gives the physics, not a safety rating. Real friction, rope stretch and the machine's own weight change the numbers, and lifting gear needs rated equipment and a competent person. For turning forces on a shaft or bolt, see the torque calculator.