Friction Force Calculator

Calculate static and kinetic friction from the normal force and coefficient of friction.

About Friction Force Calculator

Friction depends on the normal force, not the contact area, and on an incline the normal force falls with the cosine of the angle while the sliding component rises with the sine. The object slides when the sine term exceeds maximum static friction. Static friction always exceeds kinetic, which is why an object takes more force to start moving than to keep moving — and why anti-lock brakes exist.

Formula

Friction Force

f = μ N, with N = m g cos θ on an incline

μ: Coefficient of friction
N: Normal force perpendicular to the surface

Worked example

With the default values below, Friction Force Calculator returns Kinetic Friction Force of 220.725. Change any input above and every figure here is recalculated in your browser.

Inputs used

Massminimum 0 kg: 50 kg
Static coefficient of frictionaccepts 0–3: 0.6
Kinetic coefficient of frictionaccepts 0–3: 0.45
Surface angle from horizontalaccepts 0–89 degrees: 0 degrees

Results

Kinetic Friction Force: 220.725 N
Maximum Static Friction: 294.300 N
Normal Force: 490.500 N
Force Needed to Start It Moving: 294.300 N
Will It Slide Under Gravity Alone: No — static friction holds it in place

Step by step

1Values used
2Friction Force
3Kinetic Friction Force= 220.725 N
4Maximum Static Friction= 294.300 N
5Normal Force= 490.500 N
6Force Needed to Start It Moving= 294.300 N
7Will It Slide Under Gravity Alone= No — static friction holds it in place

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Friction Force calculated?

f = μ N, with N = m g cos θ on an incline Friction depends on the normal force, not the contact area, and on an incline the normal force falls with the cosine of the angle while the sliding component rises with the sine. The object slides when the sine term exceeds maximum static friction.

Why does Friction Force matter?

Static friction always exceeds kinetic, which is why an object takes more force to start moving than to keep moving — and why anti-lock brakes exist.

What values do I need to enter?

This calculator takes 4 inputs: Mass, Static coefficient of friction, Kinetic coefficient of friction, Surface angle from horizontal. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.