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R-Value Heat Loss Calculator

Steady-state Q = ΔT · A / R for a wall section.

Compute the steady-state heat-loss rate through a wall, ceiling, or floor section from its R-value, surface area, and temperature difference: Q = ΔT · A / R (in Imperial: BTU/h).

Marcus Laurent By Marcus Laurent
Published Last reviewed 1 min read

Inputs

ft²
°F

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

Q (BTU/h) = ΔT °F · A ft² / R

In depth

Compute the steady-state heat-loss rate through a wall, ceiling, or floor section from its R-value, surface area, and temperature difference: Q = ΔT · A / R (in Imperial: BTU/h).