How this calculator works
Select the first capacity band that covers the room area. Heavy shade reduces the table load by 10%, strong sun adds 10%, a kitchen adds 4000 Btu/h and each occupant beyond two adds 600 Btu/h. As an estimating assumption, ceiling heights above the table reference of 8 ft scale the base load proportionally. Reverse mode selects the largest complete table band supported by your capacity; the result stops at 2500 ft2.
Formula
adjusted Btu/h = table capacity x sunlight factor x max(1, height / 2.4384 m) + kitchen allowance + 600 x max(people - 2, 0).
Worked example
A 200 ft2 bedroom with an 8 ft ceiling and two occupants falls in the 6000 Btu/h band. A 9000 Btu/h unit supports up to 400 ft2 under the same conditions.
Advertisement
Frequently asked questions
Can I enter a very small room?
The published table begins at 100 ft2. For smaller rooms, obtain product sizing advice rather than extending the table downward.
Does a bigger unit cool better?
Excess capacity can shorten cycles and reduce moisture removal. Match capacity to the room and product guidance.
Are attic and basement multipliers automatic?
No. Those rooms can have very different insulation and moisture loads. This tool applies the published kitchen adjustment only; unusual rooms need an assessed load.