Room AC Size Calculator (BTU)
Find the window or room air conditioner size in BTU for a room, using ENERGY STAR's sizing chart and adjustments.
Cooling capacity to look for
6,000 BTU/h
- Room area
- 240 ft²
- Chart size for that area
- 6,000 BTU/h
- Adjustments
- None
- In tons and kilowatts
- 0.5 tons · 1.76 kW
The chart assumes 8-foot ceilings — go a little bigger for higher ceilings. Oversizing doesn't cool better: the unit short-cycles and leaves the room clammy.
Show the work
Room area
A = length × width
12 × 20 = 240 ft²
ENERGY STAR chart size
chart row: under 250 ft²
6,000 BTU/h
How it works
Capacity from the ENERGY STAR chart for the room's square feet (e.g. 150 up to 250 ft² → 6,000 BTU/h); −10% if heavily shaded, +10% if very sunny, +600 BTU/h per regular occupant over two, +4,000 BTU/h in a kitchen
Questions
- How does the room AC size calculator (BTU) work?
- Capacity from the ENERGY STAR chart for the room's square feet (e.g. 150 up to 250 ft² → 6,000 BTU/h); −10% if heavily shaded, +10% if very sunny, +600 BTU/h per regular occupant over two, +4,000 BTU/h in a kitchen.
- What do I need to enter?
- Room length, Room width, Sunlight, People regularly in the room, Is it a kitchen?. Optional fields can be left blank.
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