Friction Force Calculator

Friction opposes sliding with f = μN, where μ is the coefficient of friction and N the normal force pressing the surfaces together. Solve for any of the three quantities.

How to interpret the result

Friction is proportional to how hard the surfaces are pressed together (N), not to the contact area. A larger μ means grippier surfaces — rubber on asphalt (~0.9) versus ice on steel (~0.03).

Assumptions

• Coulomb (dry) friction model: f = μN
• Surfaces are not lubricated
• μ is the static or kinetic coefficient as appropriate to the situation