Thermal Expansion Calculator

How it works

1. 1Enter the coefficient of linear thermal expansion α (e.g. 12×10⁻⁶ /K for steel, 23×10⁻⁶ /K for aluminium).
2. 2Enter the original length L and the temperature change ΔT. Toggle metric (m, Δ°C) or imperial (ft, Δ°F).
3. 3The calculator applies ΔL = α·L·ΔT and shows the change in length, the equivalent in mm, and the new length.

Use cases

• Engineers sizing expansion joints in steel or concrete bridges and buildings.
• Mechanical clearance changes in shafts, bearings, and pipework over temperature.
• Electronics — solder-joint stress from mismatched expansion between materials.

Frequently asked questions

What is the formula for linear thermal expansion?

ΔL = α·L·ΔT, where α is the coefficient in 1/K, L is the original length, and ΔT is the temperature change in kelvin (= Δ°C). A 10 m steel beam (α ≈ 12×10⁻⁶ /K) warming 50 °C expands 12×10⁻⁶ × 10 × 50 = 0.006 m = 6 mm.

What are typical α values?

Steel ≈ 12×10⁻⁶, aluminium ≈ 23×10⁻⁶, copper ≈ 17×10⁻⁶, concrete ≈ 10–12×10⁻⁶, borosilicate glass ≈ 3.3×10⁻⁶, Invar ≈ 1.2×10⁻⁶ /K. Check a datasheet for precision work.

Does it matter whether ΔT is in °C or °F?

A 1 °C difference equals 1 K, so α values per kelvin apply directly to Celsius differences. In imperial mode the Δ°F input is converted to kelvin (÷ 1.8) before the formula, so the result is always correct.