Fulcrum Interactive Calculator — Lever Force & Mechanical Advantage

Robbie Dickson
2026-03-05T13:27:49-08:00

Free fulcrum calculator for Class 1, 2 & 3 levers. Solve output force, effort required, mechanical advantage, and fulcrum position. Animated diagram.

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Fulcrum Calculator — Lever Force, Mechanical Advantage & Fulcrum Position | FIRGELLI

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.

Lever Class:
Class 1 Effort – Fulcrum – Load Class 2 Effort – Load – Fulcrum Class 3 Load – Effort – Fulcrum

Metric Imperial

Find Output Force Find Effort Required Find Fulcrum Position Mechanical Advantage

⚙️ Input Parameters

Class 1 Lever (Effort – Fulcrum – Load): Fulcrum sits between effort and load — like a seesaw or crowbar. Both forces act in the same direction. MA can be above or below 1 depending on arm lengths.

Effort Force (Fe)
N

Effort Arm Length (L1)
mm

Load Arm Length (L2)
mm

Load Force (Fl)
N

Effort Arm Length (L1)
mm

Load Arm Length (L2)
mm

Effort Force (Fe)
N

Load Force (Fl)
N

Total Beam Length
mm

Effort Arm Length (L1)
mm

Load Arm Length (L2)
mm

Safety Factor: 1.5×

Calculate

📹 Video Walkthrough — How to Use This Calculator

📊 Results & Diagram

Mechanical Advantage

Result

—

Mech. Advantage

—

× (dimensionless)

Effort Arm (L1)

—

mm

Load Arm (L2)

—

mm

Lever Principle: Fe × L1 = Fr × L2 | MA = L1 ÷ L2

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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.

Lever Class
Class 1: Effort-Fulcrum-Load

Class 2: Fulcrum-Load-Effort

Class 3: Fulcrum-Effort-Load

Effort Force 100 N

Effort Arm 200 mm

Load Arm 150 mm

Load Force 200 N

OUTPUT FORCE

133 N

MECH. ADVANTAGE

1.33

EQUILIBRIUM

BALANCED

FIRGELLI Automations — Interactive Engineering Calculators

How to Use This Calculator

1. Select your lever class — Class 1, 2, or 3 — using the buttons at the top to match your physical setup.

2. Choose what you want to solve for: Output Force, Effort Required, Fulcrum Position, or Mechanical Advantage.

3. Enter your known force and arm length values in the input fields. Switch between metric (N, mm) and imperial (lbf, in) using the toggle.

4. 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.

Frequently Asked Questions

What is a fulcrum and how does it work? +

A fulcrum is the fixed pivot point around which a lever rotates. When effort is applied to one side of the lever, the fulcrum transmits that rotational force to the load on the other side. The ratio of the distances from the fulcrum to the effort and load points — known as the mechanical advantage — determines how much the lever multiplies or reduces the applied force.

How do you calculate mechanical advantage? +

Mechanical Advantage (MA) = Effort Arm Length ÷ Load Arm Length. If MA is greater than 1, you apply less force than the load requires. If MA equals 2, you only need half the force. If MA is less than 1, you apply more force than the load — but the load moves faster and further than your effort point. All lever classes follow the same base equation: Effort Force × Effort Arm = Load Force × Load Arm.

What is the difference between Class 1, 2, and 3 levers? +

Class 1 levers have the fulcrum between effort and load (seesaw, crowbar, scissors) — MA can be above or below 1. Class 2 levers have the load between the fulcrum and effort (wheelbarrow, bottle opener) — MA is always above 1, always multiplying force. Class 3 levers have effort between the fulcrum and load (tweezers, forearm, fishing rod) — MA is always below 1, trading force for speed and range of motion.

How do I find the ideal fulcrum position for a given force ratio? +

For a Class 1 lever: Effort Arm = (Load Force × Beam Length) ÷ (Effort Force + Load Force). Move the fulcrum closer to the load to increase mechanical advantage. For Class 2: Load Arm = (Effort Force × Beam Length) ÷ Load Force, where beam length is the full effort arm from fulcrum to effort. For Class 3: Effort Arm = (Load Force × Beam Length) ÷ Effort Force, where beam length equals the full load arm.

What safety factor should I use for actuator lever applications? +

FIRGELLI recommends a minimum safety factor of 1.5× for most automation applications. For high-cycle duty, outdoor environments, or safety-critical installations, use 2.0× or higher. Note that actuators should not be run continuously above 80% of rated force, which provides an additional built-in margin on top of your design safety factor.

How does a lever relate to selecting a linear actuator? +

In actuator applications such as hatch lifts, panel flips, and door openers, the actuator acts as the effort force in a lever system. The hinge point is the fulcrum. The load's centre of gravity determines the load arm length. A short actuator mounting bracket arm creates mechanical disadvantage — the actuator must produce far more force than the raw load weight. This is why correctly modelling the lever geometry before selecting an actuator is essential, which is exactly what FIRGELLI's calculator suite enables.

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