kW to Tons Calculator
Convert kW to tons of refrigeration (RT). 1 ton = 3.51685 kW. Live calculator for chillers and large HVAC.
Common conversions
| Input | Result |
|---|---|
| 3.52 kW | 1.00 RT |
| 7 kW | 1.99 RT |
| 10 kW | 2.84 RT |
| 17.58 kW | 5.00 RT |
| 35 kW | 9.95 RT |
| 70 kW | 19.90 RT |
| 100 kW | 28.43 RT |
| 200 kW | 56.87 RT |
The math behind it
- Tons = 60 / 3.51685
- Tons ≈ 17.06
Everything you need to know
"Tons" in air conditioning has nothing to do with weight. It's a unit of cooling power inherited from the ice industry, and converting it to kW lets you compare cooling equipment on a single, modern scale.
What a ton of refrigeration really means
Before mechanical refrigeration, buildings and railcars were cooled with blocks of ice. A ton of refrigeration was defined as the cooling effect of melting one short ton (2,000 lb) of ice over 24 hours, which works out to exactly 12,000 BTU/hr, or 3.51685 kW. The unit stuck around long after ice cooling disappeared, and it's still the standard way US manufacturers rate chillers and large air conditioners.
Residential AC sizing rules of thumb
Contractors commonly use a rule of thumb of roughly 1 ton per 400 to 600 square feet of conditioned space, though climate, insulation, ceiling height, and window area all shift that number. A well-insulated 2,000 sq ft home in a mild climate might need only 3 tons (10.55 kW), while the same size home in a hot, poorly insulated climate could need 5 tons (17.58 kW) or more. These rules of thumb are useful for a rough estimate only; a proper Manual J load calculation accounts for insulation, orientation, and local climate data.
kW vs tons in commercial and industrial cooling
Large chillers, process cooling, and data center cooling plants are frequently specified in kW rather than tons, especially when the equipment or engineering standard is European or metric. Converting between the two is routine: a 500 kW process chiller is about 142 tons, and a 200-ton commercial chiller is about 703 kW. Getting the conversion right avoids under-sizing, a nuisance for comfort cooling, or over-sizing, which wastes capital on oversized equipment.
Common applications
Process loads are usually engineered in kW. Convert to tons to shop North American chiller catalogues.
IT load in kW × 1.0 (sensible) translates directly into refrigeration tons needed for the CRAH/CRAC units.
European and Asian cooling equipment is rated in kW, while US catalogues use tons. Converting lets buyers compare specs from different manufacturers on the same scale.
When replacing an old tons-rated chiller with a newer kW-rated unit, converting ensures the replacement matches or exceeds the original cooling capacity.
Common mistakes
Always add 10-20% to the calculated tonnage to allow for ambient extremes and equipment aging.
A '5-ton' chiller doesn't weigh 5 tons and has nothing to do with mass. It produces about 17.58 kW of cooling.
Cooling output and electrical input are different numbers. A 10-ton unit produces about 35.2 kW of cooling but might only draw 10-12 kW of electricity.
Using 3.5 instead of 3.51685 introduces a small error that compounds on large systems; a 500-ton plant's error grows to several kW.
Frequently asked questions
Is a 1-ton AC 1 kW?+
No. One ton of refrigeration equals about 3.52 kW of cooling output, not 1 kW. The electrical input to produce that cooling is much lower, typically 1.0 to 1.3 kW.
How many kW is a 3-ton AC unit?+
About 10.55 kW of cooling output, using 3 × 3.51685. Electrical draw is closer to 3-4 kW depending on efficiency.
Is a refrigeration ton the same as a ton of weight?+
No. A ton of refrigeration is a unit of cooling power (3.51685 kW), named after the cooling effect of melting one short ton (2,000 lb) of ice in 24 hours. It has nothing to do with the weight of equipment.
Why is the conversion factor 3.51685 and not a round number?+
It comes from the energy needed to melt one short ton of ice over 24 hours, converted to kW. The original definition used imperial units (BTU and tons), so the metric equivalent isn't round.
How many kW does a 100-ton chiller need?+
A 100-ton chiller produces about 351.7 kW of cooling. Electrical input, driven by the chiller's COP, is typically 70-100 kW.
What's the difference between cooling kW and electrical kW?+
Cooling kW measures the heat removed from a space. Electrical kW measures the energy the compressor actually consumes. Divide cooling kW by the equipment's COP to estimate electrical draw.
Do data centers use tons or kW for cooling?+
Both. IT load is measured in kW, but many CRAC/CRAH units and chiller plants are still rated in tons, so converting between the two is a routine part of cooling design.
Is 1 ton exactly 12,000 BTU/hr?+
Yes. 1 ton of refrigeration is defined as exactly 12,000 BTU/hr, which equals 3.51685 kW.
How much bigger is a 20-ton unit than a 5-ton unit?+
Four times the cooling capacity: 5 tons is about 17.58 kW, and 20 tons is about 70.34 kW.