Heat Transfer Calculator

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Conduction, convection and radiation give a rate in watts. Q = mcΔT gives a total energy.
Material property. Fiberglass insulation ~ 0.04, glass ~ 0.8, concrete ~ 1.7, steel ~ 50, aluminum ~ 237, copper ~ 401.
W/(m·K)
Area through which heat flows, perpendicular to the flow direction.
Hot-side temperature minus cold-side temperature. A 1 K difference equals a 1 °C difference.
K (= °C)
Distance the heat travels through the material.
For the rate modes: turns a steady heat loss in watts into an energy and money cost over a period.
Currency
Heat transfer rate
80W
Heat flux (per m²)8W/m²
Thermal resistance (R = d/k)2.5m²·K/W
80 W
Trickle<20Modest20-100Notable100-250High250+

Heat flows through at 80 watts.

  • Fourier law: the rate rises with conductivity, area, and temperature difference, and falls as the material gets thicker.
  • The thermal resistance R = d/k is 2.5 m²·K/W; doubling the thickness halves the heat flow.
  • A higher k (metals) conducts heat fast; a low k (insulation, air) slows it down.

Next stepTo cut heat loss, increase thickness or pick a lower-conductivity material, both raise the thermal resistance.

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