BTU Calculator for Room Air Conditioners
Find the air conditioner size a room needs, using ENERGY STAR’s chart and adjustments.
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BTU per Hour
- Room area
- Chart capacity
- Adjustments
- Tons
- Kilowatts
- Buy
Rooms
Items you add are saved in this browser.
| Room | Sq. Ft. | BTU/hr | Notes | Remove |
|---|
How Many BTUs Do I Need?
ENERGY STAR sizes room air conditioners by floor area, then adjusts for sun, people and cooking heat. Too small and the room never cools; too big and the unit cycles off before it pulls the humidity out, leaving the room cold and clammy.
Area = length × width → capacity from the table below
Heavily shaded: −10% Very sunny: +10% Each person over two: +600 BTU/hr Kitchen: +4,000 BTU/hr
Worked Example
ENERGY STAR Room AC Sizing
| Area to Cool (Sq. Ft.) | Capacity (BTU/hr) |
|---|
From ENERGY STAR's room air conditioner sizing sheet, including its adjustments for shade, sun, occupants and kitchens.
Tips
Round up to the next size you can buy. For more than about 1,000 square feet, or for a whole house, a central system or mini-split sized with a Manual J load calculation is the right tool. Ceilings over 8 feet, poor insulation and west-facing windows all add load.