AC Tonnage Calculator

Inputs

Results update as you type.

Space
ft²
ft
Conditions
Cooling load, thousand BTU/hCooling load, thousand BTU/hFloor area × climate30kAfter ceiling and sun30kPeople over two+1.2kTotal, 2.5 ton31.2kmyconstructioncalculator.com
Diagram updates as you type.

Results

Check the working before you order.

Recommended AC size
2.5ton
Cooling load31,200 BTU/h
Cooling load in kW9.14 kW
Exact tonnage2.60 tons
Area per ton461.5 ft² per ton
Or 1.5 ton units2 units

This is a rule-of-thumb size for choosing a unit. For a central system or a new house, ask for a room-by-room heat-gain calculation (ACCA Manual J or similar).

Price This optional: add your own prices

Your prices are remembered on this device only.

Working
  1. Base load = 1,200 ft² × 25 BTU/h per ft² = 30,000 BTU/h
  2. Ceiling 8 ft or lower: no height adjustment
  3. Sun: × 1; people over two: + 1,200 BTU/h; kitchen: + 0 BTU/h
  4. Cooling load = 31,200 BTU/h ÷ 12,000 = 2.60 tons (9.14 kW)
  5. Size: smallest standard unit covering 95% of the load (2.47 t) = 2.5 ton

Results are estimates for planning and material ordering only. They are not a substitute for structural design or approval by a qualified engineer. Read the full disclaimer.

AC Tonnage Calculator byMy Construction Calculator: free construction calculators with the working shown.