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Tons to BTU Calculator

Convert cooling tons to BTU per hour and kilowatts.

Your measurementsEvery assumption editable01
CapacityCalculated live02

Result

36000BTU/hr

3 tons = 36000 BTU/hr

Tons of refrigeration
3
BTU per hour12,000 BTU/hr per ton, by definition
36000
In kilowattsthermal, not electrical input
10.551 kW
Nominal sizehow equipment is usually labelled
36k

A ton of refrigeration is the rate of cooling produced by melting one short ton of ice over 24 hours. It has nothing to do with the weight of the equipment, which is the assumption most people arrive with.

The kilowatt figure here is thermal output, not electrical consumption. How much power the system draws to produce it depends on its efficiency — divide the BTU/hr by the SEER to get watts.

Nominal sizes are labels, not measurements. A unit sold as 3 tons may be rated at 34,000 or 36,600 BTU/hr depending on the model, and the nameplate is the authority.

Twelve thousand BTU per hour per ton, by definition. This converts in both directions and gives the kilowatt equivalent — and explains why a unit of cooling is measured in a unit of weight at all.

Why use this tool?What it does differently03

Why use this tool?

All three units

Tons, BTU per hour and kilowatts, plus the nominal label equipment is sold under.

Explains the unit

A ton of refrigeration comes from melting ice, not from equipment weight — the assumption most people arrive with.

Thermal, not electrical

The kilowatt figure is heat moved, not power consumed. Those differ by the system's efficiency.

Nominal versus rated

Flags that a unit sold as 3 tons may be rated at 34,000 or 36,600 BTU/hr.

How this worksThe method04

How this tons to btu calculator works

One ton of refrigeration equals 12,000 BTU per hour by definition, so the conversion is a straight multiplication. The kilowatt figure divides BTU per hour by 3,412.14.

The definition comes from ice: a ton of refrigeration is the rate of cooling produced by melting one short ton of ice over twenty-four hours. It dates from when cooling was literally delivered as ice, and it survives because the industry standardised on it.

The kilowatt figure is thermal output — heat moved — rather than electrical input. How much power the system draws to move it depends on efficiency, which is what SEER measures.

How to use itStep by step05

How to use it

  1. Step 1: Enter the tonnage

    From the nameplate or the model number, which usually encodes it.

  2. Step 2: Read the BTU figure

    12,000 per ton, which is the number most equipment is labelled with.

  3. Step 3: Check against the nameplate

    Nominal sizes are labels. The rated capacity on the plate is the authority.

  4. Step 4: Do not confuse thermal with electrical

    The kilowatt figure is heat moved, not electricity consumed.

Example usageWorked figures06

Example usage

A 3 ton system
36,000 BTU per hour, or 10.551 kilowatts of heat moved. Labelled as 36k.
A 2.5 ton system
30,000 BTU per hour, 8.79 kW. Half-ton steps are standard in residential equipment.
A 12,000 BTU window unit
Exactly one ton — which is why a 12k mini split head and a one-ton system are the same capacity.
Frequently asked questionsCommon questions07

Frequently asked questions

How many BTU is one ton of cooling?

12,000 BTU per hour, by definition. A 3 ton system is nominally 36,000 BTU/hr.

Why is cooling measured in tons?

Because it originally was ice. One ton of refrigeration is the cooling produced by melting a short ton of ice over 24 hours, from the era when cooling was delivered by the block.

Does tonnage relate to the weight of the unit?

No. It is a rate of heat removal, not a mass. This is the single most common misunderstanding about the unit.

Is a 3 ton unit exactly 36,000 BTU?

Nominally. Actual rated capacity varies by model — a unit sold as 3 tons may be rated anywhere from about 34,000 to 36,600 BTU/hr. The nameplate governs.

How do I read tonnage from a model number?

Most manufacturers encode BTU in thousands or tonnage in twelfths within the model number, so 036 usually means 36,000 BTU or 3 tons. Conventions vary by brand.

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