Room AC BTU Calculator (ENERGY STAR Sizing)

Room air-conditioner capacity using the ENERGY STAR sizing chart and its adjustments for sun, occupants and kitchens.

Formula

Base BTU from the ENERGY STAR area chart; −10% heavily shaded, +10% very sunny, +600 BTU per person above 2, +4,000 BTU for a kitchen.

Worked example

Inputs: Room area = 350 sq ft; Sun exposure = normal; Regular occupants = 2; Used as kitchen = 0.

Btu	8,000
Tons	0.67

FAQ

Can I use this for central AC?

No. Whole-house systems should be sized with an ACCA Manual J load calculation.

What is a ton?

12,000 BTU per hour.

Sources

ENERGY STAR room air conditioner sizing chart

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Last reviewed 2026-10-11.