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Friction Calculator

Calculate friction force from a known normal force or a mass on an incline. Compare static friction with its limit, then estimate kinetic friction and net force if the object slides.

The positive direction is down the slope; on a horizontal surface it is simply the chosen positive axis. Applied force uses the same signed direction. Use coefficients for the actual materials and conditions.

Ideal Coulomb-friction estimate. Static friction varies up to μsN; kinetic friction is μkN. Coefficients depend on materials and conditions. This does not model rolling, deformation, vibration, heat, wear or safety limits and is not engineering advice.

How do I calculate friction force?

Static friction adjusts up to its maximum, μs × normal force. If the object slides, kinetic friction is μk × normal force and acts opposite its motion. On an incline, gravity also acts along the slope.

Frequently asked questions

How do I calculate friction force?

Static friction adjusts up to its maximum, μs × normal force. If the object slides, kinetic friction is μk × normal force and acts opposite its motion. On an incline, gravity also acts along the slope.

Are my measurements uploaded?

No. The calculation runs in this browser. Your mass, force, angle and coefficients are not uploaded or saved by this tool.

What is the difference between static and kinetic friction?

Static friction prevents motion and adjusts only as much as needed, up to μsN. Once sliding starts, kinetic friction is modeled as μkN opposite the direction of motion.

How does an incline affect friction?

For a mass on a straight incline, normal force is mg cos(θ), while gravity along the slope is mg sin(θ). The calculator compares this downslope force plus your applied force with the static-friction limit.

Does the calculator know the coefficient for my materials?

No. Friction coefficients vary with materials, surface condition, temperature and other conditions. Enter a value from a suitable reference or measurement; this estimate does not select safe engineering values.