BTU Calculator (Air Conditioning)
Estimate the cooling power (BTU/h) needed for a room from its floor area.
Result
Cooling power (BTU/h)
5,375
Power (kW)
1.58
How it works
Air-conditioning capacity is quoted in BTU per hour, and a common rule of thumb allows roughly 215 BTU/h per square metre of floor area. A 25 m² room therefore needs about 5,400 BTU/h, or a little over 1.5 kW of cooling. Floor area is only the starting point. Large windows, west-facing walls, poor insulation, a top floor under a hot roof, a busy kitchen or several occupants all raise the requirement — sometimes by half again. High ceilings matter too, since what you actually cool is a volume, not a surface. BTU per hour is a rate of heat removal, which is why it converts to kilowatts: 1 kW ≈ 3,412 BTU/h. Treat the result as a sizing estimate for comparing units, and let an installer confirm it against your actual room before you buy.
Advertisement
Frequently asked questions
How many BTU do I need?
About 215 BTU/h per m² as a baseline — a 25 m² room needs roughly 5,400 BTU/h.
What raises the BTU needed?
Strong sun, high ceilings, many people, kitchens and poor insulation all increase it.
Is an oversized air conditioner a problem?
Yes. Too much capacity cools the air fast, then shuts off before it has removed much humidity, leaving a room that feels cold and clammy. The short cycling also wears the compressor and wastes energy — correct sizing beats extra power.
Advertisement