This converter moves between the units engineers use to describe cooling capacity, heating capacity, and airflow. Enter a value in any field — tons, BTU/hr, kW, or MBH — and the others update instantly. It is the fastest way to translate a chiller or rooftop rating into the units a schedule, a load report, or a manufacturer’s data sheet happens to use.
The airflow row estimates supply CFM from cooling tons at a chosen CFM-per-ton ratio (defaulting to 400 CFM/ton). Change the ratio and the airflow updates for the same capacity; type an airflow instead and the capacity follows at that ratio. That airflow figure is a rule-of-thumb starting point for comfort cooling, not a substitute for an actual coil selection, which depends on the entering and leaving air conditions and the sensible heat ratio.
Formula & Method
Cooling capacity
1 ton = 12,000 BTU/hr = 3.51685 kW = 12 MBH
Power
1 kW = 3,412.14 BTU/hr · 1 MBH = 1,000 BTU/hr
Airflow estimate
CFM = tons × (CFM/ton), default 400 CFM/ton
Sensible relation
Q (BTU/hr) = 1.08 × CFM × ΔT (°F), at sea level
The ton of refrigeration is defined as 12,000 BTU/hr; the kW relation uses the International Table Btu (1 Btu = 1,055.056 J, NIST SP 811), so 1 kW = 3,412.14 BTU/hr. Every field is computed from the value you typed, never from another rounded field, so conversions don’t drift. The sensible-heat factor of 1.08 = 60 min/hr × 0.075 lb/ft³ × 0.24 Btu/lb·°F applies at standard sea-level air density; it drops at altitude. The 400 CFM/ton default is a conservative comfort-cooling rule of thumb — real coils run roughly 350–450 CFM/ton.
Frequently Asked Questions
How many BTU/hr are in a ton of cooling?
One ton of refrigeration equals 12,000 BTU/hr. The unit comes from the heat absorbed by melting one short ton (2,000 lb) of ice over 24 hours. In SI units, one ton equals about 3.517 kW, so 12,000 BTU/hr divided by 3,412 BTU/hr per kW gives 3.517 kW. This converter also expresses capacity in MBH, where 1 MBH equals 1,000 BTU/hr.
Why does this tool use 400 CFM per ton?
About 400 CFM per ton is a common rule of thumb for standard comfort-cooling coils with roughly a 20 degree F supply-to-room temperature difference. The airflow side of this converter defaults to 400 CFM per ton but lets you enter your own ratio, and keeps it when you change the capacity. Real coils run anywhere from about 350 to 450 CFM per ton depending on the sensible heat ratio, so confirm with an actual coil selection.
How do I convert kW to BTU/hr and tons?
Multiply kilowatts by 3,412.14 to get BTU/hr (1 kW = 3,412.14 BTU/hr). To get tons, divide kW by 3.5169, or divide the BTU/hr result by 12,000. This converter performs all of these at once: enter a value in any cooling field and the other cooling-capacity fields and the airflow estimate update together. The heating pair (MBH and kW) converts on its own.
Is CFM the same on the heating and cooling side?
The airflow estimate in this tool is tied to cooling capacity at the assumed CFM-per-ton ratio. Heating capacity is converted separately between MBH and kW because heating airflow depends on the supply-air temperature rise, which differs from cooling. Use the sensible relation Q = 1.08 times CFM times delta-T to relate airflow and heating capacity at a specific temperature rise.
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