About

Miscalculating cooling capacity leads to undersized HVAC systems, premature compressor failure, and wasted energy budgets. The relationship between BTU/hr and tons of refrigeration is fixed by ASHRAE standards: 1 ton of refrigeration = 12,000 BTU/hr, derived from the energy required to melt 1 short ton (2,000 lb) of ice at 32°F over 24 hours. This converter applies that exact factor with no rounding until the final display. Note: this tool assumes steady-state conditions and does not account for transient thermal loads, duct losses, or altitude derating factors that may apply in field sizing.

Formulas

The conversion between BTU per hour and tons of refrigeration uses a single linear factor defined by ASHRAE and based on the latent heat of fusion of ice.

T = Q12,000

Where T = cooling capacity in tons of refrigeration, Q = heat removal rate in BTU/hr, and 12,000 is the conversion constant (BTU/hr per ton).

The inverse operation recovers BTU/hr from tons:

Q = T × 12,000

The constant 12,000 derives from: 1 short ton of ice = 2,000 lb, latent heat of fusion = 144 BTU/lb, melted over 24 hr. Therefore: 2,000 × 14424 = 12,000 BTU/hr.

Reference Data

Equipment Type	Typical Capacity (Tons)	Equivalent (BTU/hr)	Typical Application
Window AC Unit (Small)	0.42	5,000	Single small room
Window AC Unit (Medium)	0.83	10,000	Bedroom / small office
Portable AC Unit	1.17	14,000	Server closet / studio
Mini-Split (Residential)	1.5	18,000	Living room / master bedroom
Central AC (Small Home)	2.0	24,000	Apartment / small house
Central AC (Medium Home)	3.0	36,000	3-bedroom house
Central AC (Large Home)	5.0	60,000	Large house / duplex
Light Commercial Rooftop	7.5	90,000	Small retail / restaurant
Commercial Rooftop Unit	10.0	120,000	Office floor / clinic
Commercial Packaged Unit	15.0	180,000	Medium commercial space
Commercial Split System	20.0	240,000	Large office / warehouse
Small Chiller	30.0	360,000	Multi-story office building
Medium Chiller	50.0	600,000	Hotel / hospital wing
Large Chiller	100.0	1,200,000	Large hospital / campus
Industrial Chiller	200.0	2,400,000	Manufacturing plant
Central Plant (Small Campus)	500.0	6,000,000	University / data center
Central Plant (Large Campus)	1,000.0	12,000,000	District cooling system
District Cooling Station	2,500.0	30,000,000	City district / airport

Frequently Asked Questions

The value comes from the energy needed to melt 1 short ton (2,000 lb) of ice at 32°F over a 24-hour period. Ice has a latent heat of fusion of 144 BTU/lb. Multiplying 2,000 × 144 gives 288,000 BTU total, and dividing by 24 hours yields exactly 12,000 BTU/hr. This definition was standardized by ASHRAE and has been the industry norm since mechanical refrigeration began.

No. A "ton of refrigeration" (RT) is a unit of cooling power, not mass. It is based on the US short ton (2,000 lb), not the metric tonne (1,000 kg) or the imperial long ton (2,240 lb). Some international standards use the metric ton of refrigeration, which equals approximately 13,898 BTU/hr (3.517 kW), but in North American HVAC practice the short-ton definition (12,000 BTU/hr = 3.517 kW) is universally assumed.

The mathematical conversion factor (12,000 BTU/hr per ton) does not change with altitude. However, HVAC equipment rated at a certain tonnage will deliver reduced actual cooling at high elevations because air density drops roughly 3% per 1,000 ft above sea level. Equipment manufacturers publish altitude derating charts - typically a 5-10% capacity reduction at 5,000 ft. This converter gives the theoretical value; field sizing must apply the derating separately.

Tons of refrigeration is a rate (power), so it maps to BTU/hr, not to BTU (energy). If you have a total BTU value, divide it by the number of hours over which that energy is exchanged to get BTU/hr first, then convert. For example, 48,000 BTU over 2 hours equals 24,000 BTU/hr, which equals 2.0 tons.

1 ton of refrigeration equals approximately 3.51685 kW of cooling (thermal). This is derived from 12,000 BTU/hr × 0.000293071 kW per BTU/hr. Do not confuse this thermal kW with the electrical kW the compressor consumes - a unit rated at 5 tons (17.58 kW thermal) might draw only 5-6 kW electrical, depending on its coefficient of performance (COP).

A common rule of thumb is 20 BTU/hr per square foot of living space in a temperate US climate. A 1,500 sq ft house would need roughly 30,000 BTU/hr, or 2.5 tons. This is a rough guideline only. Actual load calculations (ACCA Manual J) account for insulation R-values, window area, occupant count, kitchen heat gain, duct leakage, and local design temperatures. Over-sizing causes short-cycling and humidity problems.