How It Works
This calculator converts square footage into a recommended AC tonnage using the standard HVAC rule of thumb: 20 BTU per square foot, then dividing by 12,000 (1 ton = 12,000 BTU). Sun exposure, occupants, and kitchens adjust the base load.
Calculation Explanation
Tonnage = (Area × 20 × sun factor + people bonus + kitchen bonus) ÷ 12,000.
Example: a 1,000 sq ft house with normal sun and 2 people needs 1,000 × 20 = 20,000 BTU. 20,000 ÷ 12,000 = 1.67 tons, so you'd round up to a 2-ton system.
Not sure about your room dimensions? Start with the BTU Calculator to compute by room size, or use the HVAC Load Calculator for a heating-and-cooling load estimate.
AC Size by Square Footage (Quick Reference)
| Area (sq ft) | BTU | AC Tonnage |
|---|---|---|
| 300–450 | 9,000–12,000 | 1 ton |
| 450–600 | 12,000–18,000 | 1.5 ton |
| 600–900 | 18,000–24,000 | 2 ton |
| 900–1,200 | 24,000–30,000 | 2.5 ton |
| 1,200–1,600 | 30,000–36,000 | 3 ton |
| 1,600–2,200 | 36,000–48,000 | 3.5–4 ton |
Table assumes average insulation and 8-ft ceilings. Hot climates and poor insulation increase the load.