Fulcrum Calculator — Lever & Principle of Moments
Solve any lever problem: enter three of the four values (effort force, load force, effort arm, load arm) and the calculator finds the fourth using the principle of moments.
Solve for
N
m
m
Result from the principle of moments: Effort × Effort Arm = Load × Load Arm
- 1
Load moment
Load × Load Arm = 100 × 2 = 200 N·m - 2
Effort force
Moment ÷ Effort Arm = 200 ÷ 4 = 50
How does this calculator work?
The lever principle of moments: Effort × Effort Arm = Load × Load Arm. Mechanical advantage = Effort Arm ÷ Load Arm — a longer effort arm means less force is needed. Enter any three of the four quantities to solve for the fourth. Ideal levers are frictionless; real levers require slightly more effort.
Formula
How this is calculated
A lever is a rigid beam pivoting on a fulcrum. The principle of moments (or torque balance) states that the system is in equilibrium when the turning effect on each side of the fulcrum is equal: Effort × Effort Arm = Load × Load Arm. This can be rearranged to find any one unknown given the other three.
Mechanical advantage (MA) is the ratio of the effort arm to the load arm: MA = d_effort ÷ d_load. An MA greater than 1 means a small effort lifts a larger load — for example, a 4 m effort arm vs a 2 m load arm gives an MA of 2, so you lift a 100 N load with only 50 N of effort. An MA less than 1 trades force for speed or distance. Forces are in newtons (N); to convert kilograms of weight to newtons, multiply by 9.81 (standard gravity).
This calculator models an ideal frictionless lever with negligible beam weight. Real levers have friction at the fulcrum and the beam itself has mass, so the actual effort required is slightly higher than the theoretical value. The three classes of lever (where the fulcrum, effort and load are positioned) all obey the same moment equation — only the spatial arrangement differs.
Frequently asked questions
Multiply the mass in kilograms by 9.81 (standard gravitational acceleration). A 100 kg object has a weight of 981 N. For rough estimates, use 10 × kg.
Class 1 (fulcrum between effort and load — e.g. a seesaw), Class 2 (load between fulcrum and effort — e.g. a wheelbarrow) and Class 3 (effort between fulcrum and load — e.g. tweezers). All three obey the same moment equation.
Torque equals force times perpendicular distance. A longer arm applies the same moment with less force because the product Effort × d_effort must equal Load × d_load for balance. Doubling the effort arm halves the required effort.
Also known as
TG we-Calculate Editorial Team. (2026). Fulcrum Calculator — Lever & Principle of Moments [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/fulcrum-calculator
TG we-Calculate Editorial Team. "Fulcrum Calculator — Lever & Principle of Moments." TG we-Calculate. 2026. https://we-calculate.com/calculator/fulcrum-calculator.
TG we-Calculate Editorial Team, "Fulcrum Calculator — Lever & Principle of Moments," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/fulcrum-calculator
@misc{wecalculate_fulcrum_calculator, title = {Fulcrum Calculator — Lever & Principle of Moments}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/fulcrum-calculator}}, year = {2026}, note = {TG we-Calculate} }
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