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Coefficient of Friction Calculator

Compute a dimensionless friction coefficient from measured friction and normal-force magnitudes, plus the corresponding angle whose tangent equals that coefficient.

Enter every field, including explicit zeros when permitted. Decimal and scientific notation are accepted; commas, fractions and blanks are rejected. Each input must be finite and no larger than 1 billion in absolute value. Observe the stated units and domain limits.

Coefficient of friction0.3
Equivalent friction angle (degrees)16.69924423

How to use this calculator

  1. Enter every quantity in the unit printed beside its field.
  2. Select Calculate or press Enter.
  3. Read the labeled results and compare them with the assumptions below.

Formula and method

Coefficient μ = friction force/normal force; equivalent friction angle φ = arctan(μ).

The calculation runs locally in your browser. If any entry is invalid or a mathematical condition is undefined, the prior result is hidden so it cannot be mistaken for a new answer.

Worked example

Using Friction force (N) = 150, Normal force (N) = 500, the formula returns Coefficient of friction = 0.3, Equivalent friction angle (degrees) = 16.69924423. The displayed default result is generated from these same inputs.

Limitations and safety

A friction coefficient depends on materials, surface condition, speed and whether motion is starting or sliding. Do not use a generic result to rate brakes, climbing systems, slopes or lifting safety. Results use floating-point arithmetic and are displayed to about 10 significant digits; measurement uncertainty usually supports fewer. Verify units before relying on a result.

Frequently asked questions

Is static friction the same as kinetic friction?

No. Use measurements from the regime you mean to analyze; the limiting static coefficient often differs from the sliding value.

Why might a measured result differ?

The formula isolates the stated model. Real systems can add uncertainty, losses, changing properties, geometry or forces that are not among the inputs.

How should I handle units?

Convert every value to the unit shown beside its field before calculating. A numerically valid value in the wrong unit will still produce a wrong result.

Review notes and reference

Reviewed October 3, 2026. The default example and an independent edge or scaling case were checked against expected values. The live script was also checked for blank, text, comma-formatted, non-finite and out-of-range entries. Method reference. Constants use the values stated in the formula. This page’s explanation and example are original.

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