Calculate how much a bar, pipe, rail or beam changes in length when the temperature changes. Pick the material, enter the length and the temperature change. Free, private, and runs entirely in your browser.
A solid changes length in proportion to its original length, its temperature change and a material constant called the coefficient of linear thermal expansion. The calculator multiplies the three together.
How much does a steel rail expand? Carbon steel grows about 0.012 mm per meter per degree Celsius, so a 10 m rail warming by 40 °C grows about 4.8 mm.
Which material expands most? Plastics such as PVC expand several times more than metals, and aluminum expands about twice as much as steel.
A 10 m steel beam is heated by 40 °C. With α = 12 × 10⁻⁶ per °C, ΔL = 12 × 10⁻⁶ × 10 × 40 = 0.0048 m, which is 4.8 mm, so the new length is 10.0048 m.
Why do bridges have expansion joints? They allow the deck to grow and shrink with temperature without cracking or buckling.
Do materials shrink when cooled? Yes. Enter a negative temperature change to see the reduction in length.
Engineers noticed thermal expansion long before it was measured, since railways, bridges and pipes cracked or buckled with temperature changes. In 1896 Charles Édouard Guillaume developed Invar, a nickel and iron alloy with a very low expansion coefficient, which earned him a Nobel Prize in Physics in 1920 and is still used for precision instruments.
Use this calculator when planning pipe runs, fences, decking, rails, solar mounting and any long assembly that sees temperature swings. For a 6 m aluminum rail heated by 30 °C, the change is about 4.1 mm. Check the manufacturer data for exact coefficients.
What is the coefficient of linear expansion? The fractional change in length for each degree of temperature change, often given in 10⁻⁶ per kelvin.
Does volume also change? Yes. For small changes, the volume coefficient is about three times the linear one.