Friction Coefficient Calculator
Use our friction coefficient calculator to calculate the coefficient of friction (μ) from normal force and friction force. Includes the friction coefficient formula, units, and FAQs like can friction coefficient be greater than 1 or negative.
What Is the Coefficient of Friction?
The coefficient of friction (μ) describes how strongly two surfaces resist sliding against each other. It is the ratio of friction force to the normal force pressing the surfaces together.
Because it’s a ratio of forces, μ has no units. A larger value means more resistance to sliding for the same normal force.
This calculator uses friction force (F) and normal force (N), both in lbf, to return the friction coefficient μ.
Friction Coefficient Formula
Coefficient of friction is friction force divided by normal force.
F is friction force and N is normal force. Both must be in the same force units.
Useful if you know μ and want to calculate friction force.
A μ of 0.30 means friction force is 30% of the normal force.
How to Find Friction Coefficient
- 1
Enter the normal force (N) in lbf.
- 2
Enter the friction force (F) in lbf.
- 3
The calculator computes μ = F ÷ N.
Frequently Asked Questions
It’s calculated by dividing friction force by normal force: μ = F ÷ N.
The coefficient of friction is unitless because it’s a ratio of two forces.
Yes. Some material pairs (especially with strong adhesion or very high grip) can have μ values above 1.
In standard contact friction models, μ is not negative. A negative result typically means a sign convention issue (for example, using a friction force direction opposite your chosen positive direction).
On an incline, the normal force is N = W × cos(angle) (for weight W). If you can measure or compute friction force along the surface, you still use μ = F ÷ N.