Air Conditioner BTU Calculator

Your details

The longest wall of the room.
ft
The shorter wall of the room.
ft
Ceilings taller than 8 ft increase the volume of air that needs cooling.
ft
Kitchens add 4,000 BTU/hr for appliance heat. Attics add 15% for roof heat gain.
Sunny rooms need about 10% more capacity; heavily shaded rooms need about 10% less.
Well-insulated spaces retain conditioned air and require less BTU capacity.
Hotter climates mean higher design temperatures and larger required capacity.
Each person beyond the first two adds about 600 BTU/hr to the cooling load.
people
Each standard window adds roughly 1,000 BTU/hr of solar and conduction gain.
windows
Recommended capacityMid-size room unit
10,000BTU/hr

Total adjusted cooling capacity needed

Tons of cooling0.83tons
Floor area300ft²
BTU per sq ft33.3BTU/ft²
Equivalent watts2,857W
10,000 BTU/hr
Small room<8000Medium room8000-14000Large room14000-24000Whole floor24000-36000Central system36000+

This room needs a 10,000 BTU/hr unit (0.83 tons).

  • Your 300 sq ft space needs about 10,000 BTU/hr (0.8 tons) of cooling capacity.

Next stepA portable or window air conditioner in this size range is widely available. Look for an Energy Star model to minimise running costs.

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