BTU Requirement
6,360 BTU cooling, 3,840 BTU heating · 0.53 AC tons
Recommended ≥ required × 1.1 (10% headroom). Undersized units (red) won't cool the room.
Round up to the next standard size: AC units come in 0.5-ton steps (6,000, 9,000, 12,000, 18,000, 24,000 BTU). Picking 1,500-3,000 BTU above the calculated need accounts for door-opening losses and ensures the unit doesn't run at 100% on the hottest day. Don't oversize — too-large AC short-cycles, fails to dehumidify, and wastes energy.
Step-by-step calculation
Formula
Cooling BTU = area × base BTU/sq ft × ceiling factor × sun factor × insulation factor × room factor + occupants. AC tons = BTU ÷ 12,000.
- 1Floor area: 16 × 12 = 192.0 sq ft.
- 2Climate (Hot): base cooling = 192 sq ft × 30 BTU/sq ft.
- 3Adjustments: × 1.00 (ceiling height) × 1 (Normal exposure) × 1 (Average (most homes)) × 1 (Living room).
- 4+ 1 extra occupants × 600 BTU each.
- 5= 6,360 BTU/hr cooling.
- 6Heating BTU calculated similarly with climate-specific base; result = 3,840 BTU/hr.
- 71 ton of AC = 12,000 BTU/hr → 0.53 tons.