Friction Calculator
Calculate the force of friction using the coefficient of friction and normal force. Supports static and kinetic friction.
On flat surface: N = m × g
Enter the coefficient of friction and normal force.
Friction Formula
f = μ × N
Where f is the friction force, μ is the coefficient of friction, and N is the normal force (perpendicular to the surface).
Example: A 10 kg block on a surface with μ = 0.4
Normal force = 10 × 9.81 = 98.1 N
Friction = 0.4 × 98.1 = 39.24 N
Normal force = 10 × 9.81 = 98.1 N
Friction = 0.4 × 98.1 = 39.24 N
Static vs Kinetic Friction
- Static friction (μₛ): Prevents an object from starting to move. Maximum static friction = μₛ × N.
- Kinetic friction (μₖ): Acts on a moving object. Always μₖ ≤ μₛ.
Common Coefficients of Friction
| Surface Pair | μₛ (static) | μₖ (kinetic) |
|---|---|---|
| Rubber on concrete | 1.0 | 0.8 |
| Wood on wood | 0.5 | 0.3 |
| Steel on steel | 0.6 | 0.4 |
| Ice on ice | 0.1 | 0.03 |
FAQ
Can the coefficient of friction be greater than 1?
Yes. Rubber on rough surfaces can have μ > 1. The coefficient is not limited to values less than 1.
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Last updated: 2026-08-08