Thermal Conduction Calculator

How it works

1. 1Enter the material’s thermal conductivity k in W/(m·K), the cross-sectional area A, the temperature difference ΔT, and the thickness L.
2. 2The calculator applies Fourier’s law Q/t = k·A·ΔT ÷ L for the steady-state heat-flow rate in watts.
3. 3Switch metric/imperial — area in m²/ft², ΔT in Δ°C/Δ°F, and thickness in cm/inches are converted to SI first.

Use cases

• Estimating heat loss through a wall, window, or insulation panel in energy audits.
• Comparing insulation materials by varying k for a fixed geometry.
• Sizing heating or cooling systems from the required thermal power.

Frequently asked questions

What is Fourier’s law of conduction?

The steady-state heat-flow rate through a slab equals Q/t = k·A·ΔT ÷ L, where k is thermal conductivity, A is area, ΔT is the temperature difference, and L is thickness. The result is in watts with SI inputs.

What are typical thermal conductivity values?

Still air ≈ 0.025, mineral wool ≈ 0.04, timber ≈ 0.12, brick ≈ 0.7, glass ≈ 1, concrete ≈ 1.7, aluminium ≈ 200, copper ≈ 400 W/(m·K). Metals conduct far better than insulation.

Can you show a worked example?

A brick wall (k = 0.7), 3 m², 0.2 m thick, 15 °C warmer inside: Q/t = 0.7 × 3 × 15 ÷ 0.2 = 157.5 W. Over an hour that is ≈ 567 kJ conducted through the wall.