What Size AC Do I Need for 400 Square Feet?

Answer
9,000 BTU/h for 400 sq ft

By the Energy Star room AC sizing chart, a 400 ft² room needs about 9,000 BTU/h (2.64 kW, 0.75 ton). Make it 10,000 BTU if the room is very sunny or 9,000 BTU if it is heavily shaded; add 600 BTU per person above two and 4,000 BTU for a kitchen.

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Recommended AC capacity
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How we calculated this

    For estimating and educational purposes only. Results are approximate and are not a substitute for a licensed professional, the manufacturer's instructions or your local code. Disclaimer

    More questions like this

    BTU Chart by Room Size150 sq ft250 sq ft300 sq ft500 sq ft1,000 sq ftAll quick answers

    AC size for a 400 sq ft room

    SituationBTU/h
    Average room, 2 people9,000
    Very sunny (+10%)10,000
    Heavily shaded (−10%)9,000
    4 people11,000
    Kitchen (+4,000 BTU)13,000
    Poor insulation / top floor11,000

    Rule-of-thumb sizing for single rooms with 8 ft ceilings. Window units come in 5,000–24,000 BTU; mini-splits in 9,000–36,000 BTU.

    Frequently asked questions

    Is 9,000 BTU enough for 400 sq ft with a kitchen?

    Not quite: add 4,000 BTU for the kitchen, so about 13,000 BTU.

    How many tons is 9,000 BTU?

    0.75 ton. One ton of cooling is 12,000 BTU/h.

    Open the full calculator: AC BTU Calculator: What Size Air Conditioner Do I Need? →