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Room AC BTU calculator

Quick answer: ENERGY STAR sizes room air conditioners by floor area: about 5,000 BTU for 100–150 sq ft, 6,000 for 150–250, 8,000 for 300–350 and 10,000 for 400–450 sq ft. Then reduce 10% for a heavily shaded room, add 10% for a very sunny one, add 600 BTU per person over two and 4,000 BTU for a kitchen.

  • Manufacturer bag yields · published coverage rates
  • Updated
  • Reviewed by Alex · How we calculate

Based on the ENERGY STAR room air conditioner sizing chart.

Area (sq ft)BTU/hr
100–1505,000
150–2506,000
250–3007,000
300–3508,000
350–4009,000
400–45010,000
450–55012,000
550–70014,000
700–100018,000
1000–120021,000
1200–140023,000
1400–150024,000

Adjustments (ENERGY STAR): reduce 10% for a heavily shaded room, add 10% for a very sunny room, add 600 BTU per person over two, add 4,000 BTU for a kitchen.

Frequently asked questions

What happens if the AC is too big?

An oversized unit cycles on and off and removes less humidity.