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Tons, BTU/h and kW Conversion Chart

Conversions between tons of refrigeration, BTU per hour and kilowatts of cooling capacity, with a quick lookup table for common equipment sizes.

Ref HV-0053NIST SP 811

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

Cooling capacity is stated in three common units:

Ton of refrigeration (TR): 12,000 BTU/h. It comes from the heat needed to melt one short ton of ice in 24 hours.
BTU/h: British thermal units per hour. MBH means 1,000 BTU/h.
kW (thermal): the SI unit, used on metric and export equipment. This is kW of cooling, not electrical input.

How to use it

Tons to BTU/h: multiply by 12,000.
BTU/h to tons: divide by 12,000.
Tons to kW: multiply by 3.517.
kW to BTU/h: multiply by 3,412.
BTU/h to W: multiply by 0.2931.
EER to COP: divide EER by 3.412.

Conversion chart

Tons	BTU/h	MBH	kW (approx.)
1	12,000	12	3.52
1.5	18,000	18	5.28
2	24,000	24	7.03
2.5	30,000	30	8.79
3	36,000	36	10.55
3.5	42,000	42	12.31
4	48,000	48	14.07
5	60,000	60	17.58
7.5	90,000	90	26.38
10	120,000	120	35.17
20	240,000	240	70.34

Key points

Nominal tons are not rated capacity. A "3-ton" unit is a size class. Its actual capacity at given conditions comes from the AHRI certificate or the manufacturer's expanded performance data.
In model numbers, the size often appears as thousands of BTU/h (for example 024, 036, 048 for 2, 3 and 4 tons). This is a convention, not a rule.
Heating capacity uses the same units. Furnace input and output are both in BTU/h; they differ by efficiency.
Electrical input (kW) and cooling output (kW) are different numbers. Their ratio is the COP.

Common mistakes

Treating kW on a metric nameplate as electrical draw when it is cooling output.
Assuming a nominal 3-ton unit delivers 36,000 BTU/h at every condition.
Confusing MBH (thousand BTU/h) with MMBH (million BTU/h).

Governing standards: NIST SP 811 (unit conversion factors); AHRI certified ratings and manufacturer performance data for actual capacity.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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