Coefficient of Friction Calculator
Use our coefficient of friction calculator to find the coefficient of friction between objects given the friction force and normal force acting on it.
Coefficient of Friction:
Coefficient of Friction Formula
Friction Force Formula
Normal Force Formula
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How to Find the Coefficient of Friction
The coefficient of friction (μ) is a dimensionless scalar value that quantifies the amount of frictional resistance one surface exerts on another when they are in contact. The coefficient of friction depends not only on the materials making up the two surfaces but also on their condition—whether they are smooth, rough, lubricated, or contaminated.
You can calculate the coefficient of friction using a variation of the friction force equation.
Coefficient of Friction Equation
You can find the coefficient of friction using the formula:
μ = 𝑓 / N
Where:
μ = coefficient of friction
𝑓 = force of friction
N = normal force
You can find the forces exerted on an object using our friction force and normal force calculators.
For example, let’s calculate the force of friction resisting a wooden block with a coefficient of friction of 0.4 between it and the surface it sits on and a normal force action on it of 100 Newtons.
𝑓 = 0.4 × 100 N
𝑓 = 40 N
Thus, the frictional force that acts to resist the sliding of the wooden block is 40 Newtons.
What Factors Affect the Coefficient of Friction
Material Properties: Different materials exhibit varying levels of roughness and adhesion characteristics, significantly influencing the coefficient of friction. For example, rubber on concrete has a high coefficient due to high grip, whereas ice on metal has a very low coefficient due to minimal interaction at the contact surface.
Surface Condition: The presence of lubricants, contaminants, or wear can alter the coefficient of friction. Lubrication generally reduces friction, making the surfaces smoother and less adhesive, while contaminants such as dust or grime can either increase or decrease friction depending on their nature.
Normal Force: While the coefficient itself does not depend on the normal force, the actual frictional force does. In most common scenarios, the coefficient of friction remains constant over a range of normal forces. However, at very high pressures or loads, the surfaces might deform, altering the real area of contact, which can affect the coefficient.