Friction force
F_f = mu x N
Material property lookup
Friction Coefficients of Common Materials
Compare approximate static and kinetic friction coefficients for dry, lubricated, polymer, rubber, wood, and ice contact pairs.
Instant friction lookup
Select a material or case
Select a material pair to view approximate static and kinetic friction coefficients.
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Reference table
Friction coefficient table
| Material Pair | Group | Static Coefficient | Kinetic Coefficient | Notes |
|---|---|---|---|---|
| Steel on Steel, dry | Metal pair | 0.60 | 0.40 | Clean dry surfaces |
| Steel on Steel, lubricated | Metal pair | 0.15 | 0.05 | Lubricant and finish dependent |
| Aluminum on Steel | Metal pair | 0.45 | 0.30 | Approximate dry value |
| Copper on Steel | Metal pair | 0.53 | 0.36 | Approximate dry value |
| Brass on Steel | Metal pair | 0.51 | 0.35 | Approximate dry value |
| PTFE on Steel | Polymer pair | 0.04 | 0.04 | Low-friction polymer |
| Nylon on Steel | Polymer pair | 0.25 | 0.20 | Moisture and finish dependent |
| Rubber on Dry Concrete | Tire/contact | 0.90 | 0.70 | Approximate dry traction |
| Rubber on Wet Concrete | Tire/contact | 0.60 | 0.45 | Condition dependent |
| Wood on Wood | Wood pair | 0.40 | 0.30 | Grain and moisture dependent |
| Ice on Ice | Ice pair | 0.10 | 0.03 | Temperature dependent |
Formulas
Friction formulas
Incline limit
tan(theta) = mu_s
At impending slip
Friction coefficients are approximate and highly sensitive to surface finish, lubrication, contamination, speed, temperature, and contact pressure.
Reference
How engineers use friction coefficients
Sliding resistance
Kinetic friction estimates force while surfaces slide.
Slip prevention
Static friction estimates whether a contact will begin to move.
Machine design
Friction affects brakes, clutches, guides, bearings, fasteners, and wear.
Testing
Critical designs should use measured friction values for the actual surface condition.
FAQ
Friction coefficient questions
What is coefficient of friction?
It is the ratio of friction force to normal force between two contacting surfaces.
Is static friction higher than kinetic friction?
For many material pairs, static friction is higher than kinetic friction.
Why do friction values vary so much?
Surface finish, lubrication, contamination, wear, speed, load, and temperature all affect friction.
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