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# Air conditioner tonnage calculator

Size an air conditioner in tons and BTU/h from room dimensions, sun, occupants, insulation, and heat sources, with the load breakdown shown.

Enter the room dimensions to size the unit.

One ton of cooling is 12,000 BTU/h, about 3.52 kW; the ton is a marketing size, so the estimate also shows the standard unit size it snaps up to. The chart underneath is the ENERGY STAR room table with published rule adjustments: 10 percent either way for sun, 600 BTU/h per person past two, 4,000 BTU/h for a kitchen, height over 8 ft scaling the load, 3.412 BTU/h per watt of appliances, and 15 percent extra for poor insulation. A real ducted or mini-split install needs a proper load calculation, so treat this as a starting point before you talk to an installer. Oversizing cools fast but short cycles, which leaves a clammy room and a shorter-lived compressor.
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## More unit & math tools

- [Unit converter](/converters/units)
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