Tons, BTU and square feet — the conversions
One ton of cooling = 12,000 BTU/hr. Equipment is sold in half-ton steps, and the amount of floor area one ton can handle depends on climate: roughly 400–500 sq ft per ton in hot southern climates, 500–600 in mixed climates, and 600–700 in northern states with mild summers.
| Tonnage | BTU/hr | Hot climate | Mixed | Cool |
|---|---|---|---|---|
| 1.5 tons | 18,000 | ~700 sq ft | ~850 sq ft | ~1,000 sq ft |
| 2 tons | 24,000 | ~900 | ~1,100 | ~1,300 |
| 2.5 tons | 30,000 | ~1,150 | ~1,400 | ~1,650 |
| 3 tons | 36,000 | ~1,350 | ~1,650 | ~1,950 |
| 3.5 tons | 42,000 | ~1,600 | ~1,950 | ~2,300 |
| 4 tons | 48,000 | ~1,800 | ~2,200 | ~2,600 |
| 5 tons | 60,000 | ~2,250 | ~2,750 | ~3,250 |
How to find the tonnage of your current unit
Look at the model number on the outdoor condenser's data plate. Most manufacturers encode BTU in thousands: 24 = 2 tons, 30 = 2.5, 36 = 3, 42 = 3.5, 48 = 4, 60 = 5 tons. For example, a model like XR14036 is a 3-ton unit. This is the fastest way to check what you have before replacing it — but do not blindly replace like-for-like if the old unit short-cycled or never kept up.
Frequently asked questions
How many square feet does a 3-ton unit cover?
Roughly 1,350 sq ft in hot climates, 1,650 in mixed climates and up to 1,950 sq ft in cool northern climates with average insulation.
How do I convert BTU to tons?
Divide BTU per hour by 12,000. A 36,000 BTU unit is 3 tons; a 48,000 BTU unit is 4 tons.
What tonnage do I need per square foot?
Plan on one ton per 400–500 sq ft in hot climates, 500–600 in mixed climates and 600–700 in cool climates — then confirm with a full load calculation.
Can I install a bigger tonnage than I need?
You can, but you should not: oversized ACs short-cycle, leave humidity behind and cost more upfront and monthly. Match tonnage to the load.