Conduction Heat Transfer Calculator
Heat conduction is the transfer of thermal energy through a material from a region of higher temperature to lower temperature without bulk motion. Fourier's law quantifies this: the heat flow rate Q (in Watts) equals the material's thermal conductivity k times the cross-sectional area A times the temperature difference dT, all divided by the thickness L. This formula is used in engineering to design insulation, heat exchangers, building envelopes, and electronic cooling systems. Enter the material properties and geometry below to calculate the steady-state heat transfer rate.
Fourier's conduction formula
Q = k × A × dT / L
Q is the heat flow rate in Watts; k is thermal conductivity in W/(m K); A is cross-sectional area in m^2; dT is the temperature difference in Kelvin (or degrees C); L is thickness in meters. Heat flux (power per unit area) is q = k dT / L.
Common thermal conductivities
- Copper: 401 W/(m K) (excellent heat conductor, used in heat sinks)
- Aluminum: 205 W/(m K) (common in heat exchangers)
- Stainless steel: 15 W/(m K)
- Glass: 1.0 W/(m K)
- Brick: 0.6-1.0 W/(m K)
- Wood (pine): 0.11-0.17 W/(m K)
- Fiberglass insulation: 0.04 W/(m K)
- Still air: 0.026 W/(m K)
Frequently asked questions
What is Fourier's law of heat conduction?
Fourier's law states that the rate of heat transfer by conduction equals the thermal conductivity of the material (k) times the cross-sectional area (A) times the temperature difference (dT) divided by the thickness (L): Q = k A dT / L.
What are the units?
Heat flow rate Q is in Watts (W). Thermal conductivity k is in W/(m K). Area A is in square meters (m^2). Temperature difference dT is in Kelvin or Celsius (same difference). Thickness L is in meters (m).
What is thermal conductivity k?
Thermal conductivity is a material property measuring how well it conducts heat. Typical values: copper 401 W/(m K), aluminum 205 W/(m K), glass 1.0 W/(m K), wood 0.12-0.17 W/(m K), air 0.026 W/(m K). Values sourced from NIST.
How does conduction differ from convection and radiation?
Conduction transfers heat through direct molecular contact without bulk movement. Convection transfers heat via fluid movement (liquid or gas). Radiation transfers heat via electromagnetic waves and requires no medium.
How is this used in building insulation?
In building construction, Fourier's law underlies R-value calculations. A higher R-value material has lower thermal conductivity or greater thickness, reducing heat flow per unit area. The ASHRAE Fundamentals handbook tabulates R-values for building materials.
Official sources
- NIST: NIST Thermal Conductivity Data.
- ASHRAE: ASHRAE Handbook of Fundamentals.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.