Estimate the air conditioner cooling capacity (BTU) a room needs from its size, sun and occupants.
Understanding the btu calculation
This BTU calculator estimates the cooling power an air conditioner needs for a room. Enter the floor area and adjust for sun exposure, extra occupants and whether it’s a kitchen.
It uses the common rule of about 20 BTU per square foot, with standard adjustments.
Try it with these numbers
The calculator opens with a room area of 300. On those figures the cooling needed is 6,000. Underneath, Base comes out at 6,000 BTU and Occupant load at 0 BTU. Change any field and every figure updates as you type.
How to use it
- Enter the room area in square feet.
- Set the number of occupants and sun exposure.
- Read the recommended BTU rating.
Formula reference
base = area × 20 BTU
+600 per extra person, +4,000 for a kitchen, × sun factor
Frequently asked questions
How many BTU do I need per square foot?
About 20 BTU per square foot is the standard starting point, adjusted for sun, occupancy and heat sources.
Does room use matter?
Yes — kitchens need more (about +4,000 BTU), and rooms with lots of sun or many people need extra capacity.
Can an AC be too big?
Yes — an oversized unit cools fast but cycles off before removing humidity, leaving the room clammy. Sizing matters.