When you're sizing a linear actuator for a hatch lift, panel flip, or any pivoting load, the lever geometry between your actuator mounting point, the hinge, and the load's centre of gravity determines exactly how much force you need — get it wrong and your actuator is undersized before you even start. Use this Fulcrum Calculator to calculate output force, effort required, mechanical advantage, and ideal fulcrum position using lever class, arm lengths, and applied forces. That matters for actuator selection, mechanical design, and any application where force multiplication or reduction is part of the engineering brief — robotics, industrial automation, and structural mechanisms. This page includes the governing lever formula, a worked example, full theory for Class 1, 2, and 3 levers, and an FAQ.
What is a fulcrum?
A fulcrum is the fixed pivot point that a lever rotates around. Where you place it relative to the effort force and the load controls how much the lever multiplies — or reduces — the force you apply.
Simple Explanation
Think of a seesaw: the middle support is the fulcrum. Push down on one end and the other end rises. Slide the support closer to one side and a small push becomes a much bigger lift on the other side — that's mechanical advantage at work. Every lever, from a crowbar to a hinge on a truck tailgate, follows exactly the same principle.
⚖️ Fulcrum Calculator
Calculate lever output force, effort required, mechanical advantage, and ideal fulcrum position for Class 1, 2, and 3 lever systems — with animated diagram.
📹 Video Walkthrough — How to Use This Calculator
Fulcrum interactive visualizer
Visualize how lever class, fulcrum position, and arm lengths affect mechanical advantage and force requirements. Adjust parameters to see real-time calculations for output force, effort required, and mechanical advantage.
OUTPUT FORCE
133 N
MECH. ADVANTAGE
1.33
EQUILIBRIUM
BALANCED
FIRGELLI Automations — Interactive Engineering Calculators
How to Use This Calculator
- Select your lever class — Class 1, 2, or 3 — using the buttons at the top to match your physical setup.
- Choose what you want to solve for: Output Force, Effort Required, Fulcrum Position, or Mechanical Advantage.
- Enter your known force and arm length values in the input fields. Switch between metric (N, mm) and imperial (lbf, in) using the toggle.
- Click Calculate to see your result.
Simple Example
Class 1 lever, finding output force:
- Effort Force: 100 N
- Effort Arm (L1): 500 mm
- Load Arm (L2): 250 mm
- MA = 500 ÷ 250 = 2.0 — the lever doubles your input force.
- Output Force = 100 × 2.0 = 200 N
Understanding Fulcrum Mechanics — Engineering Guide
A lever is one of the six classical simple machines, and the fulcrum is its defining element. In any lever system, the fulcrum is the fixed pivot point around which the beam rotates. The relationship between where the fulcrum sits relative to the applied effort and the load determines the lever class, the mechanical advantage, and the force trade-offs in your design.
Use the formula below to calculate lever equilibrium and mechanical advantage.
The governing equation for all lever classes is the same: Effort Force × Effort Arm = Load Force × Load Arm. This is the principle of moments — the clockwise torque around the fulcrum must equal the counter-clockwise torque for the system to be in equilibrium. All four calculation modes in this calculator are derived directly from rearranging that single equation.
Class 1 Lever
In a Class 1 lever, the fulcrum sits between the effort and the load. Examples include seesaws, crowbars, scissors, and balance scales. The mechanical advantage depends entirely on the ratio of the two arm lengths.
Place the fulcrum close to the load and you get high mechanical advantage — less effort required, but the effort must travel further. Place it close to the effort and you get speed and range of motion at the cost of increased effort.
Class 2 Lever
In a Class 2 lever, the load sits between the fulcrum and the effort application point. The fulcrum is always at one end, and the effort at the other end. Examples include wheelbarrows, bottle openers, and nutcrackers. Class 2 levers always produce a mechanical advantage greater than 1 — they always multiply force. The trade-off is that the effort must move further than the load.
Class 3 Lever
In a Class 3 lever, the effort is applied between the fulcrum and the load. Examples include tweezers, the human forearm (bicep applying effort between elbow fulcrum and hand load), and a fishing rod. Class 3 levers always have a mechanical advantage below 1 — they reduce force but amplify speed and range of motion. The load moves further and faster than the effort input.
Lever Mechanics in Linear Actuator Applications
Understanding lever geometry is critical when sizing a linear actuator for any hinged or pivoting application. When an actuator drives a lid, hatch, panel, or door, it is acting as the effort force in a lever system. The hinge is the fulcrum, and the load's centre of gravity determines the effective load arm.
A short actuator bracket arm creates significant mechanical disadvantage — the actuator must produce substantially more force than the raw weight of the load. FIRGELLI's full calculator suite handles these more complex geometries for lid lifts, panel flips, scissor lifts, and push-pull linear motion applications.
