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Air-Conditioner BTU Sizing from Room Size Calculator

BTU ≈ 20 · sqft, with adjustments for ceiling height and occupancy.

Estimate the cooling capacity (BTU/h) needed for a room from its area, ceiling height (relative to 8 ft baseline) and number of regular occupants. Default factor 20 BTU/sqft is appropriate for a typical insulated room; sun-drenched south-facing rooms may need 10 % more.

Marcus Laurent By Marcus Laurent
Published Last reviewed 1 min read

Inputs

sq ft
ft

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

BTU ≈ 20 · sqft · (ceiling_ft / 8) + 600 · (occupants − 2)

In depth

Estimate the cooling capacity (BTU/h) needed for a room from its area, ceiling height (relative to 8 ft baseline) and number of regular occupants. Default factor 20 BTU/sqft is appropriate for a typical insulated room; sun-drenched south-facing rooms may need 10 % more.