Calculator
AC Size Calculator
Estimate the tonnage your home needs. Use this to sanity-check a contractor's proposal, not to replace a Manual J load calculation.
Model reviewed August 2026
Recommended size
5 tons
Round to the nearest half ton
- Cooling load
- 61,000 BTU/hr
- Typical equipment costInstalled, 14-17 SEER2
- $8,500 – $16,000
- Rule-of-thumb check
- 400 sq ft per ton
Estimates only. Local pricing, site conditions and code requirements change the real number.
The formula
BTU = square footage x climate factor x insulation factor x ceiling adjustment; Tons = BTU / 12,000
One ton equals 12,000 BTU per hour. Hot-humid climates run roughly 25-30 BTU per square foot and mild climates closer to 18-22, but oversizing hurts humidity control in any climate.
Worked example
A 2,000 sq ft home in a hot-humid climate with average insulation and 9 ft ceilings needs roughly 54,000 BTU, or about a 4.5 ton system.
Frequently asked questions
What size AC do I need for 2,000 square feet?
In a hot-humid climate, roughly 4 to 4.5 tons for an average 2,000 sq ft home. In a mild or cold climate the same house often needs only 3 to 3.5 tons. A Manual J load calculation settles it.
Is a bigger AC better?
No. An oversized system cools quickly and shuts off before removing humidity, leaving a house clammy and shortening compressor life through short cycling.
Sources
Sources & verification
- ENERGY STAR sizing and efficiency guidance
- ACCA Manual J / Manual S sizing standards
- AHRI equipment performance directory
- International Code Council (IRC/IBC)
Model vintage August 2026. The links above are the issuing agencies' own pages — we publish them so you can confirm the current rule yourself, not as evidence that each fact on this page was re-checked with them today. Cost figures are modeled estimates based on national baselines adjusted for local labor and material pricing, not quotes. Permit rules change; confirm with the building department before starting work.