BTU to kW / kW to BTU / Tons of Refrigeration Converter (+ Airflow for a Heat Load)
HVAC and refrigeration quote capacity in five different units. Type any one of them and see all the others — plus the airflow that would carry that heat at your chosen temperature difference, which is the number a fan engineer needs.
No signup · Works on mobile · Formulas shown below · Updated 2026-08-23
Engineering estimate for preliminary sizing. Verify against the fan curve, local codes and your system measurements before purchase. Ask a Longwell engineer to check your duty point free of charge.
BTU/h and tons: North American HVAC equipment, window and split ACs, chillers.
kW: Europe, Asia, engineering data sheets, heat pumps (and the only SI unit).
kcal/h: boilers and burners in Europe/Japan; Chinese split ACs historically (2,500 kcal/h = 1 匹).
HP: compressor and fan motor sizes; a "3 HP" condensing unit means the compressor motor, not the cooling capacity.
MBH: thousands of BTU/h, used for furnaces and commercial RTUs.
For fan selection what matters is the airflow at the design ΔT: a 5-ton (17.6 kW) rooftop unit at 400 CFM/ton needs ≈ 2,000 CFM (3,400 m³/h) of supply air; its condenser rejects ≈ 22 kW and needs 2–3× that airflow at a 10–12 K rise — the duty point for the condenser fans.
Frequently Asked Questions
How many BTU is 1 kW?
1 kW = 3,412 BTU/h. So a 3.5 kW split air conditioner is a 12,000 BTU/h (1-ton) unit, and an 18,000 BTU/h unit is about 5.3 kW.
How many kW is a ton of refrigeration?
1 ton of refrigeration = 3.517 kW = 12,000 BTU/h = 3,024 kcal/h. A 5-ton unit is 17.6 kW of cooling.
How much airflow per ton of cooling?
The classic rule is 400 CFM per ton (≈ 680 m³/h per ton, or about 190 m³/h per kW) for comfort cooling with a 20 °F (11 K) supply temperature drop. Dry climates use 450 CFM/ton; humid climates 350 CFM/ton.
What is 1 匹 (HP) in BTU or kW?
In Chinese air-conditioner ratings 1 匹 is nominally 2,500 kcal/h ≈ 2.9 kW ≈ 9,900 BTU/h of cooling (derived from a 1 HP compressor input). 1.5 匹 ≈ 3.5 kW ≈ 12,000 BTU/h.
How do I convert a heat load in BTU/h to CFM?
CFM = BTU/h ÷ (1.08 × ΔT °F) for sensible heat at sea level. 10,000 BTU/h with a 20 °F temperature rise needs 463 CFM. In metric: m³/h ≈ 3 × W ÷ ΔT (K).
Link to or Cite This Tool
This calculator is free to reference in articles, forums, specifications and course material. Please credit it with a link:
<a href="https://www.longwellfans.com/resources/btu-kw-ton-converter/">BTU to kW, Tons & kcal/h Converter</a> by LONGWELL Fans
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