What is BTU in Air Conditioning?
BTU stands for British Thermal Unit. It is the international measure of energy used to define the cooling capacity of air conditioners. Specifically, it measures the amount of heat an AC unit can remove from a room in one hour.
Selecting the right BTU rating is critical. Our AI-enhanced calculator analyzes your room's thermal profile to recommend a unit that cools efficiently without spiking your electricity bill.
How to Calculate AC Size?
A simple "square footage" rule often fails because it ignores heat sources. Our calculation includes:
We apply a standard of ~25 BTU per square foot of floor space.
Human bodies radiate heat. We add ~600 BTU for every person in the room.
Kitchens generate massive heat. We automatically add a 1,200 BTU buffer if you select "Kitchen."
If your room has high ceilings (over 8ft), the standard calculation might be too low. We recommend adding 10% to the final result provided by this tool to account for the extra air volume.
General Room Size vs. BTU Chart
Typical requirements for standard rooms (assuming average ceiling height and shade).
| Room Size (Sq. Ft.) | Recommended BTU |
|---|---|
| 100 - 150 sq. ft. | 5,000 BTU |
| 150 - 250 sq. ft. | 6,000 BTU |
| 300 - 350 sq. ft. | 8,000 BTU |
| 400 - 450 sq. ft. | 10,000 BTU |
| 450 - 550 sq. ft. | 12,000 BTU |
Frequently Asked Questions
Can I buy a bigger AC just to be safe?
No. An oversized unit will cool the air too quickly and shut off before it has time to dehumidify the room. This leads to a cold but "clammy" (damp) feeling and wears out the compressor.
Does insulation matter?
Yes. Poorly insulated rooms (drafty windows, thin walls) require more power. If your insulation is poor, consider sizing up to the next available BTU level.
Disclaimer
This AI AC BTU Calculator provides estimates based on DOE (Department of Energy) guidelines. Real-world cooling needs depend on ceiling height, insulation quality, window direction, and local climate. Consult an HVAC professional for whole-house systems.