Convert an HVAC cooling-capacity rating from BTU per hour into tons of refrigeration, the unit central air systems are usually sized in.
How it works
One ton of refrigeration is defined as 12,000 BTU/hr — the rate of heat absorption needed to melt one short ton of ice in 24 hours. So tons = BTU/hr ÷ 12,000.
What this does not include
This converts a rated capacity between units — it doesn’t calculate the cooling load a specific room or building actually needs, which depends on square footage, insulation, climate and more.
How to use this calculator
- Enter the cooling capacity in BTU per hour.
- Read off the equivalent in tons.
A worked example
24,000 BTU/hr converts to 2 tons of cooling capacity — one ton equals 12,000 BTU/hr by definition.
30,000 BTU/hr converts to 2.5 tons.
What the variables mean
| Variable | Meaning |
|---|---|
| BTU | British thermal units per hour, a measure of cooling or heating capacity |
| Tons | The HVAC industry’s standard unit — 1 ton = 12,000 BTU/hr |
Edge cases worth knowing
A “ton” of air conditioning has nothing to do with weight. It originally referred to the cooling power of melting one ton of ice in 24 hours — a historical unit that’s stuck around in HVAC sizing conventions.
Zero BTU makes the tonnage zero, a degenerate but valid case — the calculator declines to show a result only when BTU is genuinely missing.
Why “tons” for a cooling rating?
The unit dates back to when ice was the standard cooling method — a “one-ton” air conditioner cools at the same rate that melting one ton of ice per day would.
What size AC unit does a typical home need?
Residential central air systems commonly range from 1.5 to 5 tons depending on home size and climate, though a proper load calculation (not covered here) is the accurate way to size one.
Is a bigger ton rating always better?
No — an oversized unit cycles on and off too quickly, cooling the air without adequately removing humidity, which can leave a room feeling clammy despite a low temperature.
