BTU Calculator

US & Canada

Enter your room size to get the air conditioner capacity in BTU, using the ENERGY STAR chart and its adjustments.

Your room

1. Room size

ft
ft

The ENERGY STAR chart assumes an 8 ft ceiling. Size up for higher ceilings.

2. Adjustments

people

Result

0

How it was worked out

From the ENERGY STAR room air conditioner sizing chart and its adjustments. Whole house systems need a proper load calculation (Manual J in the US).

The ENERGY STAR sizing chart

Room air conditioner capacity by floor area, as published by ENERGY STAR. It assumes an 8 ft ceiling.

Air conditioner BTU needed by room area
Area to be cooled Capacity needed
100 up to 150 sq ft 5,000 BTU/h
150 up to 250 sq ft 6,000 BTU/h
250 up to 300 sq ft 7,000 BTU/h
300 up to 350 sq ft 8,000 BTU/h
350 up to 400 sq ft 9,000 BTU/h
400 up to 450 sq ft 10,000 BTU/h
450 up to 550 sq ft 12,000 BTU/h
550 up to 700 sq ft 14,000 BTU/h
700 up to 1,000 sq ft 18,000 BTU/h
1,000 up to 1,200 sq ft 21,000 BTU/h
1,200 up to 1,400 sq ft 23,000 BTU/h
1,400 up to 1,500 sq ft 24,000 BTU/h
1,500 up to 2,000 sq ft 30,000 BTU/h
2,000 up to 2,500 sq ft 34,000 BTU/h

The adjustments

  • Heavily shaded room: reduce capacity by 10%
  • Very sunny room: increase capacity by 10%
  • More than two people: add 600 BTU for each extra person
  • Kitchen: add 4,000 BTU

In Canada? Room units are sold by BTU here too. Switch the calculator to metres and it converts your room size for you.

Common questions

What size air conditioner do I need for a 12x12 room?
A 12 × 12 room is 144 sq ft, which the ENERGY STAR chart puts at 5,000 BTU. Size up 10% for a very sunny room, or down 10% if it is heavily shaded.
How many BTU do I need for 500 square feet?
The ENERGY STAR chart gives 12,000 BTU for 450 up to 550 sq ft.
How many BTU for 1,000 square feet?
21,000 BTU on the ENERGY STAR chart (1,000 up to 1,200 sq ft). At that size a whole home or ductless system with a proper load calculation is usually the better route.
Is 8,000 BTU enough for 300 square feet?
Yes. The chart gives 8,000 BTU for 300 up to 350 sq ft. Go one size up if the room gets strong afternoon sun or regularly holds more than two people.
What size AC for a kitchen?
Add 4,000 BTU to the chart size, per ENERGY STAR, because of cooking heat. A 200 sq ft kitchen comes to 10,000 BTU.
Is a bigger air conditioner better?
No. ENERGY STAR warns that an oversized unit cools the room before it removes the humidity, leaving it cold and clammy, and it costs more to buy and run.
How many BTU is a ton?
One ton of cooling is 12,000 BTU per hour. A 24,000 BTU unit is a 2 ton unit.