CalcMyHVAC

What size AC do you need?

Find the right central air conditioner for your home, in tons and BTU. Your ZIP code sets the climate adjustment.

Size of your home
sq ft

Count rooms the AC will cool. Leave out the garage and unfinished basement.

Location

Enter a ZIP code and we set the climate zone for you.

Your home
ft

How to size an air conditioner

AC size is measured in tons of cooling. One ton removes 12,000 BTU of heat per hour. To find yours:

  1. Work out the cooling load in BTU. Multiply square footage by 20–30 BTU per square foot for your climate, then adjust for ceiling height, insulation and sun.
  2. Divide by 12,000 to turn BTU into tons.
  3. Pick the nearest standard size: 1.5, 2, 2.5, 3, 3.5, 4 or 5 tons. Size up only when you're more than about 5% over a size.

Tons = cooling BTU ÷ 12,000

AC size chart by square footage

Recommended central AC size for an average home with 8-foot ceilings.

Home sizeHot climateMild climateCold climate
800 sq ft2 ton2 ton1.5 ton
1,000 sq ft2.5 ton2 ton2 ton
1,200 sq ft3 ton2.5 ton2 ton
1,500 sq ft4 ton3 ton2.5 ton
1,800 sq ft5 ton4 ton3 ton
2,000 sq ft5 ton4 ton3.5 ton
2,400 sq ft2 systems5 ton4 ton
2,800 sq ft2 systems2 systems5 ton

Replacing an old unit? Don't just copy its size. Many older systems were oversized, and new windows or insulation may have lowered your load since.

Common questions

What size AC do I need for a 1,500 square foot house?

Usually 3 tons in a mild climate. In a hot southern climate expect 3.5 to 4 tons, and in a cold northern climate about 2.5 tons.

What size AC do I need for a 2,000 square foot house?

Usually 4 tons in a mild climate, 5 tons in a hot climate and 3.5 tons in a cold climate. Good insulation or a shaded lot can bring it down half a ton.

How many square feet does a ton of AC cool?

Roughly 400 to 600 square feet per ton, depending on climate. Hot climates get closer to 400 square feet per ton; cold climates closer to 600.

What happens if my AC is too big?

An oversized AC short-cycles: it cools the air fast and shuts off before removing humidity. The house feels damp, energy use goes up and the compressor wears out sooner.

What happens if my AC is too small?

An undersized AC runs nonstop on hot days and still may not reach the thermostat setting. It also wears out faster from the constant running.