CFM / Tons / BTU Converter

Bidirectional HVAC capacity and airflow unit converter
Cooling Capacity

Airflow (at standard conditions, 55°F supply, 75°F room)

Heating
1 ton = 12,000 BTU/hr 1 ton = 3.517 kW 1 ton ≈ 400 CFM (rule of thumb) 1 kW = 3,412 BTU/hr
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About This Calculator

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). 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 capacity1 ton = 12,000 BTU/hr = 3.517 kW = 12 MBH
Power1 kW = 3,412 BTU/hr  ·  1 MBH = 1,000 BTU/hr
Airflow estimateCFM = tons × (CFM/ton), default 400 CFM/ton
Sensible relationQ (BTU/hr) = 1.08 × CFM × ΔT (°F), at sea level

The ton-of-refrigeration definition (12,000 BTU/hr) and the 3.412 BTU/hr per watt energy equivalence follow standard ASHRAE Fundamentals unit relations. 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. 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 to get BTU/hr (1 kW = 3,412 BTU/hr). To get tons, divide kW by 3.517, or divide the BTU/hr result by 12,000. This converter performs all of these at once: enter a value in any field and the cooling-capacity, airflow, and heating fields update together.
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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