An HVAC system that's too small won't keep your home comfortable; too large and it short-cycles, wasting energy and humidity control. This calculator gives a rough BTU and tonnage estimate based on your home's square footage and climate.
Home Details
sq ft
Climate Zone
Hot Climate
Scenario: Your 1,800 sq ft home is in a hot climate (southern states, desert Southwest).
Result: Estimated cooling: 1,800 x 25 = 45,000 BTU, or 3.75 tons. Rounded to the nearest half-ton: 4.0 tons.
Moderate Climate
Scenario: Your 2,400 sq ft home is in a moderate climate (mid-Atlantic, Pacific Northwest).
Result: Estimated cooling: 2,400 x 20 = 48,000 BTU, or 4.0 tons. Rounded to the nearest half-ton: 4.0 tons.
Cold Climate
Scenario: Your 1,600 sq ft home is in a cold climate (upper Midwest, Northeast).
Result: Estimated heating: 1,600 x 35 = 56,000 BTU, or 4.67 tons. Rounded to the nearest half-ton: 4.5 tons.
A rough rule of thumb: hot climate = 25 BTU/sq ft, moderate = 20 BTU/sq ft, cold = 30-35 BTU/sq ft for heating. A 2,000 sq ft home in a moderate climate needs about 40,000 BTU of cooling capacity, or 3.5 tons.
In a moderate climate: 1,500 x 20 = 30,000 BTU, or 2.5 tons. In a hot climate: 1,500 x 25 = 37,500 BTU, or about 3 tons. These are rough estimates -- actual sizing depends on insulation, windows, ceiling height, and sun exposure.
One ton of cooling equals 12,000 BTU per hour. It has nothing to do with weight -- it's a legacy term from the ice-cooling era. Residential systems range from 1.5 to 5 tons, with each ton handling roughly 400-600 sq ft depending on climate and home efficiency.
Oversized units cool the air fast but shut off before removing humidity, leaving the house feeling clammy. Undersized units run constantly and can't maintain temperature on extreme days. Right-sizing gives you comfort, efficiency, and equipment longevity.
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