What size air conditioner for 1200 sq ft? BTU answer and adjustments
1200 sq ft of floor area needs roughly 24,000 BTU/h of cooling at the standard 20 BTU/sq ft — 2.00 tons, 7.0 kW. Sunny exposure pushes that to 26,400, heavy shade trims it to 21,600, a kitchen adds 4,000 (→ 28,000), and a crowd adds 600 per extra person.
| Scenario | Rule | BTU/h |
|---|---|---|
| Baseline room | 1200 × 20 | 24,000 |
| Very sunny | +10% | 26,400 |
| Heavily shaded | −10% | 21,600 |
| Kitchen | +4,000 | 28,000 |
| Four regular occupants | +600 × 2 | 25,200 |
Conversions: 12,000 BTU/h = 1 ton = 3.517 kW. 24,000 BTU/h ≈ 2.00 tons ≈ 7.0 kW. Figures are cooling capacity to look for on the spec sheet, not electrical input.
From BTU to a product
Translated to the shelf, 1200 sq ft means an 18,000–24,000 BTU mini-split, or central/ducted equipment for enclosed layouts. Take the next size up from your adjusted figure and stop there; inverter units absorb a 10–20% margin gracefully, a doubling never.
Method and the Manual J threshold in our BTU sizing guide; equipment options on window units, mini-splits and portables (read SACC, not marketing BTU).
Frequently asked questions
How many BTU for 1200 square feet?
24,000 BTU/h as a baseline (20 BTU/sq ft), 26,400 for a very sunny room, 21,600 for a shaded one, plus 4,000 for a kitchen and 600 per occupant beyond two. That is about 2.00 tons or 7.0 kW.
What size AC unit is that?
An 18,000–24,000 BTU mini-split, or central/ducted equipment for enclosed layouts. For whole-house systems serving several enclosed rooms, a Manual J load calculation replaces this room-level rule.
Is 20 BTU per square foot always right?
It is the room-unit baseline ENERGY STAR and the DOE use; ceiling height above 8 ft, poor insulation and big west glazing push it higher, while a well-insulated shaded room can sit lower. The adjustments above capture the common cases.