Friction Calculator
0.50
Type
Friction Force50.000 N
Friction is the resistive force that opposes sliding between two surfaces, and its magnitude is set by how hard the surfaces are pressed together and how rough they are. This calculator multiplies the normal force by a coefficient of friction to give the friction force, letting you switch between static friction (the maximum before motion starts) and kinetic friction (the steadier force once an object is already sliding).
Formula
F_friction = μ × N
- F_friction
- Friction force in newtons (N)
- μ
- Coefficient of friction (static or kinetic), dimensionless
- N
- Normal force pressing the surfaces together, in newtons
How it works
- Enter the normal force in newtons — the force pressing the surfaces together, often equal to the object weight on a level surface.
- Enter the coefficient of friction (a dimensionless value the calculator accepts between 0 and 1) and choose static or kinetic.
- The friction force is the coefficient times the normal force, returned in newtons and rounded to three decimal places, labelled with the friction type you selected.
Worked example
A box pressed onto a surface with a normal force of 500 N, with a static coefficient of friction of 0.6.
- Select static friction and enter μ = 0.6, N = 500.
- Apply F = μ × N: 0.6 × 500.
Static friction force = 300 N — the maximum horizontal push the box resists before it starts to slide.
Frequently asked questions
- What is the difference between static and kinetic friction?
- Static friction is the force resisting the start of motion and reaches a maximum just before sliding begins. Kinetic friction acts once the object is already moving and is usually a bit smaller, which is why it takes more effort to get something moving than to keep it moving.
- What is the normal force?
- The normal force is the perpendicular force pressing the two surfaces together. On a flat, level surface it equals the object weight (mass × gravity), but on an incline or with extra downward pressure it differs and should be computed separately.
- Why must the coefficient be between 0 and 1?
- This calculator restricts the coefficient to the 0-to-1 range, which covers most everyday surface pairs (for example rubber on dry concrete is near the top end). Some special materials exceed 1, but those are outside the inputs accepted here.
- Does surface area affect the friction force?
- No. In this model friction depends only on the coefficient and the normal force, not on the contact area. Spreading the same weight over a larger area does not change the friction force.