How to Calculate AC Tonnage from Square Footage and BTU
Air conditioner cooling capacity is measured in tons, where 1 ton of refrigeration = 12,000 BTU/hr (British Thermal Units per hour). The basic formula is: AC Tonnage = Total Cooling BTU / 12,000.
To estimate base cooling load from square footage, multiply your home area by climate zone factors (typically 20 to 30 BTU per sq ft for moderate climates, and up to 35–40 BTU per sq ft in hot southern climates). Ensure your ductwork supports proper airflow with our CFM Calculator (400 CFM per ton).
AC Tonnage Sizing Chart by Square Footage
Use this reference table to match conditioned floor area to nominal AC equipment sizes:
- 600 – 1,000 sq ft: 1.5 Tons (18,000 BTU/hr) | ~600 CFM
- 1,000 – 1,300 sq ft: 2.0 Tons (24,000 BTU/hr) | ~800 CFM
- 1,300 – 1,650 sq ft: 2.5 Tons (30,000 BTU/hr) | ~1,000 CFM
- 1,650 – 2,000 sq ft: 3.0 Tons (36,000 BTU/hr) | ~1,200 CFM
- 2,000 – 2,500 sq ft: 3.5 Tons (42,000 BTU/hr) | ~1,400 CFM
- 2,500 – 3,000 sq ft: 4.0 Tons (48,000 BTU/hr) | ~1,600 CFM
- 3,000 – 3,600 sq ft: 5.0 Tons (60,000 BTU/hr) | ~2,000 CFM
Commercial Cooling per Square Foot and Occupancy Considerations
Commercial office and retail cooling requirements differ from residential sizing because of higher internal heat gains from electronics, lighting density, and customer occupancy. Commercial spaces typically require 1 ton per 250 to 350 square feet. For winter heating balance, verify dual heat pump sizing with our Heating BTU Calculator.
