By Zencalcy Editorial TeamLast reviewed About us
Friction is proportional to the normal force pressing two surfaces together. On a flat surface the normal force is the object's weight; on an incline it drops to mg cosθ. This calculator handles both, using the coefficient you supply.
Static and kinetic friction force on flat and inclined surfaces.
F = μ · N N = m · g · cos θ
The static coefficient applies before sliding starts and is usually larger than the kinetic coefficient. Choose the one that matches the situation.
| Symbol | Meaning |
|---|---|
| μ | Coefficient of friction (dimensionless). |
| N | Normal force, in newtons. |
| m | Object mass, in kilograms. |
| θ | Surface angle above the horizontal. |
The normal force is 98.07 N, so the friction force is 0.3 × 98.07 = 29.42 N.
Continue with the Ground Speed Calculator, Horizontal Projectile Motion Calculator, or the Impulse and Momentum Calculator — or browse more kinematics tools and all physics calculators.
Rubber on dry asphalt is about 0.7 to 0.9, steel on steel about 0.15 to 0.6, and ice on steel around 0.03.
Results are computed from the standard equations of classical mechanics. Unit conversions use the SI definitions published by NIST. Air resistance is ignored unless the calculator names a drag model.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026