Lever Calculator

A lever balances about its fulcrum when the effort force times its arm equals the load force times its arm: effort force times effort arm equals load force times load arm. Each arm is the distance from the fulcrum to where that force acts.

Mechanical advantage equals the load force divided by the effort force, which also equals the effort arm divided by the load arm. A value of 4 means the lever lets you lift a load four times your effort.

The effort arm (de) is the distance from the fulcrum to the point where you push. The load arm (dl) is the distance from the fulcrum to the load. Both are measured along the lever, perpendicular to the force.

Exactly three. Choose the fourth in the Solve for menu and its input box disappears, so you only ever fill in the three you know. The tool rearranges the balance equation for the remaining one.

Use newtons for both forces and one consistent length unit for both arms, such as metres or centimetres. Because mechanical advantage is a ratio, its units cancel out and it stays the same whatever length unit you pick.

Yes. Every entry must be a finite number greater than zero, since a lever arm or force of zero or below has no physical meaning here. A blank or non-numeric box shows a prompt instead of a result.

Yes. The balance law holds regardless of class, so the same equation covers a seesaw (first class), a wheelbarrow (second class), and tweezers (third class). Third class levers give a mechanical advantage below one, trading force for speed or range.

No. The calculation assumes a rigid, weightless beam and ignores friction at the fulcrum. For a heavy bar you would add its weight as an extra load at its centre of mass.

No. The solve runs in your browser as you type. A JSON API exposes the same law of the lever if you want to call it from a script.