# Friction Calculator

URL: https://speedycalculator.com/calculators/physics/friction/
Last updated: 2026-10-30

> The friction calculator finds the friction force from the coefficient of friction and the normal force – or from the mass on a flat or inclined surface – using F = μN.

## Inputs

- Friction coefficient μ
- Normal force from…
- Normal force N (N, kN, MN, mN, lbf, kgf, dyn)
- Mass (kg, g, mg, t, lb, oz)
- Surface angle (°, rad, arcmin, arcsec, mrad)
- Gravitational acceleration g (m/s², ft/s², g, cm/s²)

## Results

- Normal force
- Friction force
- Angle at which an object starts sliding (static)

## Formula

```
F = μ × N,  N = m·g·cos θ on an incline
```

## Explanation

Friction resists sliding between surfaces. Static friction holds things in place up to a limit; kinetic friction acts once they slide. Tyres, brakes, shoes and screws all rely on it.

### How to use the Friction Calculator

- **Friction coefficient μ**
- **Normal force from…**
- **Normal force N**
- **Mass**
- **Surface angle**
- **Gravitational acceleration g**

Results update as you type, every field has its own unit menu, and everything is calculated in your browser.

### How it works

Enter the friction coefficient and either the normal force or the mass and slope angle. Typical values: rubber on dry asphalt 0.7–0.9, steel on steel 0.6 (dry) or 0.1 (lubricated), ice on ice 0.03.

### Inputs explained

FieldWhat to enterFriction coefficient μA numberNormal force from…Choose one: Enter the normal force, Mass on a surfaceNormal force NUnits: N, kN, MN, mN, lbf, kgf …MassUnits: kg, g, mg, t, lb, ozSurface angleUnits: °, rad, arcmin, arcsec, mradGravitational acceleration gUnits: m/s², ft/s², g, cm/s²

### What each result means

- **Friction force** = [Friction coefficient μ]×[Normal force]
- **Angle at which an object starts sliding (static)** = deg(atan([Friction coefficient μ]))

### Example values

How the main result changes when **Friction coefficient μ** changes and everything else stays at the example values above:

Friction coefficient μFriction force (N)0.31500.452250.63000.753750.94501.2600

## Worked example

Inputs — Friction coefficient μ: 0.6; Normal force from…: Enter the normal force; Normal force N: 500 N; Gravitational acceleration g: 9.80665 m/s².

Results — Normal force = 500 N; **Friction force = 300 N**; Angle at which an object starts sliding (static) = 30.96 °.

## Key terms

- **Normal force**: The force perpendicular to the contact surface.

## FAQ

**What is the difference between static and kinetic friction?**
Static friction prevents sliding up to a maximum; kinetic friction acts while sliding and is usually smaller.

**Does friction depend on contact area?**
For dry solid surfaces, approximately not.

**Can μ be greater than 1?**
Yes – racing tyres and rubber on rough surfaces can exceed 1.

**What is the angle of repose?**
arctan(μs), the steepest slope on which an object stays put.


## Sources

- [OpenStax – University Physics Volume 1](https://openstax.org/details/books/university-physics-volume-1)
- [HyperPhysics (Georgia State University)](http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html)