Updated
Using Window air conditioner size calculator
Look up room cooling capacity from the ENERGY STAR area table, then adjust for sun, people and kitchen use.
The ENERGY STAR room-AC guide assumes an 8-foot ceiling. Shade reduces the table value by 10%; strong sun increases it by 10%. Add 600 BTU/h per person above two and 4,000 BTU/h for a kitchen. This is a preliminary room-unit estimate, not a whole-building HVAC load calculation. At a shared table boundary this tool uses the next larger band.
A worked example
For room area (square feet) = 200, sun exposure = Ordinary, regular occupants = 2, kitchen? = No, estimated cooling capacity (btu per hour) = 6000.
Before you use the result
The ENERGY STAR room-AC guide assumes an 8-foot ceiling. Shade reduces the table value by 10%; strong sun increases it by 10%. Add 600 BTU/h per person above two and 4,000 BTU/h for a kitchen. This is a preliminary room-unit estimate, not a whole-building HVAC load calculation. At a shared table boundary this tool uses the next larger band.
Example results for room area (square feet)
These examples use Sun exposure: Ordinary; Regular occupants: 2; Kitchen?: No. They are reference calculations, not recommended settings.
| Room area (square feet) | Estimated cooling capacity (BTU per hour) |
|---|---|
| 100 | 5000 |
| 200 | 6000 |
| 400 | 10000 |
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ToolOctopus. “Window air conditioner size calculator.” Updated 2026-09-29. https://tooloctopus.com/window-air-conditioner-size-calculator.
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