Thermal Expansion Calculator
Linear, area and volume — with the right multiple of α.
Work out Thermal Expansion. Linear, area and volume — with the right multiple of α. Names the counter-intuitive bit rather than hiding it.
Length, area or volume — whatever matches the mode below.
Steel 12e-6, aluminium 23e-6, concrete 12e-6, glass 9e-6, Pyrex 3.3e-6.
Change in length
0.048
Linear — coefficient α · 0.0480% of the original
Always use the LINEAR coefficient α here — the page applies the right multiple for you. Area expands as 2α and volume as 3α, and reaching for α in all three cases is the standard trap. The numbers look small and matter enormously. 100 m of steel bridge grows 48 mm over a 40 °C swing, which is why bridges have expansion joints and why rails buckle in heatwaves. A hole in a plate expands too, and by the same fraction as the plate — the material does not close in on it. That is why heating a stuck jar lid works, and how interference fits are assembled.
How the Thermal Expansion Calculator works
Enter an original size, the linear coefficient α and a temperature change. The page applies 2α for area and 3α for volume itself, which is the step most often skipped when people reach for α in all three cases.
Also known as: linear expansion calculator · coefficient of thermal expansion calculator · volume expansion calculator · how much does steel expand
Frequently asked questions
How do I calculate thermal expansion?
ΔL = αL₀ΔT for length. For area use 2α and for volume 3α, applied to the original area or volume.
Why is the volume coefficient three times the linear one?
Because the object expands in all three dimensions at once. To first order the fractional volume change is three times the fractional length change, and the second-order terms are negligible.
Does a hole in a plate get bigger or smaller when heated?
Bigger, by the same fraction as the plate. The material does not close in on it, which is why heating a stuck jar lid loosens it and how interference fits are assembled.
Why do bridges have expansion joints?
Because 100 m of steel grows about 48 mm over a 40 °C swing. Without somewhere to go, that expansion turns into enormous compressive stress — which is why rails buckle in heatwaves.
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