Science & Engineering
Lever mechanical advantage.
Ideal mechanical advantage MA = effort distance ÷ load distance from the fulcrum, and the load you can move or the effort you need, for first, second and third class levers. Runs in your browser.
Lever
Result
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Worked example
A 1.5 m bar pivots on a rock with you pushing 1.2 m from the fulcrum and the load 0.3 m from it on the other side (a first class lever). MA = 1.2 ÷ 0.3 = 4 : 1. Pushing with 150 N lifts a load of 150 × 4 = 600 N (about 61.2 kgf). Your end moves 4 times as far as the load does.
How it works
The law of the lever says the ratio of output force to input force equals the ratio of the distances from the fulcrum: MA = Fload ÷ Feffort = a ÷ b, with a the distance from the fulcrum to the effort and b the distance from the fulcrum to the load. Enter the two distances and one force and the other force follows. Because work in equals work out for an ideal lever, the effort end must travel a ÷ b times as far as the load.
Levers are grouped by what sits between the other two: first class has the fulcrum in the middle (seesaw, scissors), second class has the load in the middle (wheelbarrow, nutcracker), third class has the effort in the middle (tweezers, a hammer). Second class always gives MA above 1; third class always below 1, trading force for speed and range. Real levers lose a little to friction and bending.
Not for safety-critical design
Planning and learning aid only. It is not for structural, lifting, pressure-system or other safety-critical design, and it is not professional engineering advice. Have a qualified engineer check anything that carries people or could fail dangerously.
Sources and basis: Wikipedia: Lever; Wikipedia: Mechanical advantage. Checked 2026-10-16. Planning aid only; see the note above.
FAQ
What is the mechanical advantage of a lever?
MA = effort distance ÷ load distance, both measured from the fulcrum. A value of 4 means the load force is four times the effort force in an ideal lever.
How do I find the force needed to lift a load with a lever?
Divide the load by the mechanical advantage: effort = load × (load distance ÷ effort distance). Enter the load and the two distances.
Does the lever class change the answer?
No. The formula only uses the two distances from the fulcrum. Class describes the arrangement: first class has the fulcrum between effort and load, second the load between, third the effort between.
Why does a longer lever make lifting easier?
A longer effort distance raises MA, so less force is needed. You pay for it by moving your end a proportionally longer distance.
Is the answer exact?
It is the ideal value. Friction at the pivot, the weight of the lever and any bending are ignored, so real effort is slightly higher.