Btu Calculator
Size your air conditioner properly: enter room area, ceiling height, insulation, sun exposure and climate to get the cooling BTU per hour you need, converted to tons and watts. Undersized units never catch up; oversized ones cool fast but leave the air clammy.
TheCalculators — Btu Calculator
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Cooling Required
6,000 BTU/h
≈ 0.5 ton AC · 1758 W cooling power
- Room Area
- 300 sq ft
- Ceiling Factor
- ×1
- Recommended AC
- 0.5 ton (1 ton unit)
- Cooling Watts
- 1,758 W
- Electrical Draw (~EER 10)
- 600 W
- BTU per sq ft
- 20 BTU/h·sq ft
How the estimate builds up
Estimates assume 8 ft ceiling baseline (20 BTU/h per sq ft). Real loads depend on windows, ducts and usage.
Oversizing cools quickly but shuts off before dehumidifying, leaving rooms clammy. When between sizes, rounding up by one half-ton is usually fine for kitchens and sunny rooms.
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Formula
BTU/h = 20 × area(sq ft) × (ceiling ÷ 8) × insulation × sun × climate + 600 × extra occupants + kitchen 4,000
- • Start from 20 BTU/h per square foot of floor area.
- • Scale for ceiling height, insulation quality, sun and climate with the multipliers.
- • Add 600 BTU/h for each person beyond two, and 4,000 BTU/h for kitchens.
Pro tips
- • A 20×20 ft room (400 sq ft) typically needs ~8,000 BTU/h; a 500 sq ft living room ~12,000 (1 ton).
- • Shade trees, curtains and low-E windows can meaningfully cut the required capacity.
- • 1 ton of cooling = 12,000 BTU/h = 3.517 kW.
FAQ
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