Thermal Expansion Calculator
Enter an expansion coefficient, a length, and a temperature change to get the change in length and the new final length — and see why heating stretches a solid and cooling shrinks it.
Change and final length at once
Enter the coefficient, original length, and temperature change and the calculator returns the change in length (α·L₀·ΔT) and the final length (L₀ + ΔL) together.
Keep units consistent
Use metres for length and 1/K for the coefficient — a change of 1 K equals a change of 1 °C, so the temperature change is the same in either scale.
What is thermal expansion?
Why solids grow when heated
This thermal expansion calculator works out how much a solid object changes in length when its temperature rises or falls. Heating makes the particles in a material vibrate more and sit slightly farther apart, so most solids expand when warmed and contract when cooled. The effect is small but real, and it adds up over long spans: it is why bridges have expansion joints, why railway tracks can buckle in a heatwave, and why a tight metal lid loosens under hot water. Enter the linear coefficient of expansion, the original length, and the temperature change, and the calculator returns both the change in length and the resulting final length.
Enter the expansion coefficient, the original length in metres, and the temperature change to get the change in length and the final length instantly.
The change in length is the expansion coefficient multiplied by the original length and the temperature change. The final length is simply the original length plus that change.
ΔL = α × L₀ × ΔTTake a 10 m steel beam (coefficient α ≈ 0.000012 per kelvin) that warms by 50 °C. Multiply the coefficient by the length and the temperature change: 0.000012 × 10 × 50 = 0.006 m, a growth of 6 mm. Add that to the original length and the beam ends up 10 + 0.006 = 10.006 m long. Because the coefficient and the temperature change both enter as simple multipliers, doubling either one doubles the change in length. Different materials expand by different amounts — aluminium (≈ 0.000023) stretches roughly twice as far as steel for the same heating, while concrete and copper sit in between.
The formula is a clean linear approximation, but a few practical points are worth keeping in mind.
Linear model, consistent units, one dimension
This calculator gives the linear expansion along one dimension and assumes the coefficient stays constant over the temperature range — true for everyday swings but less accurate across hundreds of degrees, where the coefficient itself shifts. It does not cover area or volume expansion (which use roughly 2α and 3α) or phase changes such as melting. Keep your units consistent — metres for length and 1/K for the coefficient — and remember a negative temperature change means cooling, which contracts the material and returns a negative change in length.