HVAC Tonnage Calculator
Work out HVAC tonnage either from floor area (using square feet per ton for your climate) or by converting a known cooling load from BTU per hour to tons.
How to use the HVAC Tonnage Calculator
- Choose whether to calculate from floor area or from BTU.
- Enter the area and climate, or the BTU load.
- Read the tonnage and the nearest standard size.
How it works
One ton of cooling = 12,000 BTU/h (about 3.517 kW). For area-based sizing, a common rule of thumb is one ton per 400 sq ft in hot climates up to one ton per 700 sq ft in cool climates. Equipment is sold in half-ton steps from about 1.5 to 5 tons for homes.
BTU to tons
| BTU/h | Tons | kW |
|---|---|---|
| 12,000 | 1 | 3.52 |
| 18,000 | 1.5 | 5.28 |
| 24,000 | 2 | 7.03 |
| 30,000 | 2.5 | 8.79 |
| 36,000 | 3 | 10.55 |
| 42,000 | 3.5 | 12.31 |
| 48,000 | 4 | 14.07 |
| 60,000 | 5 | 17.58 |
Frequently asked questions
How many square feet does a 3-ton unit cool?
Roughly 1,200 sq ft in a hot climate to about 2,100 sq ft in a cool one.
How many BTU is 2.5 tons?
2.5 tons = 30,000 BTU/h.
How many tons is 36,000 BTU?
36,000 BTU/h is exactly 3 tons.