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Window Energy Loss Calculator

BTU/hr lost through a window from U-value and ΔT.

Compute the heat lost through a window in BTU per hour from its U-value, area, and the indoor-outdoor temperature difference.

Nadia Almasri By Nadia Almasri
Published Last reviewed 1 min read

Inputs

BTU/(hr·ft²·°F)
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 (BTU/hr, with ΔT in °F).

In depth

Compute the heat lost through a window in BTU per hour from its U-value, area, and the indoor-outdoor temperature difference.