AC Tonnage Calculator
Turn a cooling load into air conditioner tons and a standard unit size, or get a rough estimate from floor area.
- Cooling load
- Kilowatts
- Standard size
- Airflow at 400 CFM/ton
- Unit Size
Saved Sizes
Items you add are saved in this browser.
| Name | BTU/hr | Tons | Unit | Remove |
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How to Calculate AC Tonnage
A ton of cooling is 12,000 BTU per hour: the heat it takes to melt a ton of ice in 24 hours. Divide the cooling load by 12,000 to get tons, then choose the nearest standard size that covers it.
Residential central air conditioners come in half-ton steps from 1½ to 5 tons.
Worked Example
Why Square Feet per Ton Is Only a Rough Guide
Contractors often quote 400 to 600 or more square feet per ton, but the real load depends on climate, insulation, windows, shading, air leakage and duct location. A new, tight house can need half the tonnage of an old one the same size. The ACCA Manual J load calculation is the accepted method (and many codes require it), and Manual S is used to pick equipment that matches it. Oversized systems short-cycle and leave the house clammy.
Tons to BTU
| Tons | BTU/hr | kW |
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