AC Size for Room: Ton by Square Footage Table
Quick Answer: For 500 sq ft in moderate climate: 1 ton (12,000 BTU). In hot climate: 1.5 ton (18,000 BTU). Assumes 8-ft ceiling and standard insulation....
AC Size by Room Square Footage
| Room Size | Tonnage | BTU/h | System Type |
|---|---|---|---|
| 100–150 sq ft | 0.5 ton | 6,000 | Window / Mini-split |
| 150–250 sq ft | 0.5–0.75 ton | 6,000–9,000 | Window / Mini-split |
| 250–400 sq ft | 0.75–1 ton | 9,000–12,000 | Window / Mini-split |
| 400–600 sq ft | 1–1.5 ton | 12,000–18,000 | Mini-split / PTAC |
| 600–1,000 sq ft | 1.5–2 ton | 18,000–24,000 | Mini-split / Central |
| 1,000–1,500 sq ft | 2–2.5 ton | 24,000–30,000 | Central AC |
| 1,500–2,000 sq ft | 2.5–3.5 ton | 30,000–42,000 | Central AC |
| 2,000–3,000 sq ft | 3.5–5 ton | 42,000–60,000 | Central AC |
Based on ASHRAE Climate Zone 3–4, 8-ft ceilings, standard insulation. For hot climates (Zone 1–2), increase by 25%. For cold climates (Zone 5+), decrease by 15%.
Adjustment Factors
- Ceiling height > 8 ft: Multiply tonnage by (height ÷ 8)
- Poor insulation (pre-1980): Add 25–30%
- Large south/west windows (>25% wall area): Add 15%
- Hot climate (Zone 1-2): Add 25–40%
- Kitchen: Add 4,000 BTU (0.33 ton) for cooking heat
- Each person above 2: Add 600 BTU
Common Mistakes
- Oversizing "just in case": Leads to short-cycling, poor humidity control, and higher bills
- Ignoring insulation upgrades: If you've improved insulation, you may need a smaller unit
- Not considering duct condition: Leaky ducts can reduce effective capacity by 20–30%
Frequently Asked Questions
What AC size do I need for a 500 sq ft room?
For 500 sq ft in moderate climate: 1 ton (12,000 BTU). In hot climate: 1.5 ton (18,000 BTU). Assumes 8-ft ceiling and standard insulation.
How many sq ft does a 2 ton AC cool?
A 2-ton AC cools 800–1,200 sq ft in moderate climates and 600–900 sq ft in hot climates.
What AC size for a 20×20 room?
A 20×20 room is 400 sq ft. Needs 0.75–1 ton (9,000–12,000 BTU) in moderate climate. In hot climate: 1–1.5 ton.
Disclaimer: Sizing estimates are preliminary. Final equipment selection should use ACCA Manual J load calculation by a licensed HVAC contractor.