Friction Force Calculator

About this calculator

Friction force resists the relative motion (or attempted motion) between two surfaces in contact, calculated as F = μ·N, where μ is the coefficient of friction between the two materials and N is the normal force pressing them together (usually equal to weight, m·g, on a flat horizontal surface). A higher coefficient — rubber on dry asphalt, for example — produces more friction than a lower one, like steel on ice, regardless of the contact area between the surfaces.

Physics students and mechanical engineers use this formula to calculate the force needed to start moving an object (static friction) or keep it sliding at constant speed (kinetic friction), to design braking systems and tire compounds, and to determine whether an object on a ramp will stay put or slide. Enter the coefficient of friction and the normal force (or mass) to find the friction force.