basic

U-Value Window Heat Loss Calculator

Q = U · A · ΔT for a glazed opening.

Compute the heat-loss rate through a window from its U-value (BTU/h/ft²/°F), area, and inside-to-outside temperature difference: Q = U · A · ΔT.

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 = U · A · ΔT; equivalent R = 1 / U.

In depth

Compute the heat-loss rate through a window from its U-value (BTU/h/ft²/°F), area, and inside-to-outside temperature difference: Q = U · A · ΔT.