Tons to CFM Calculator
Airflow needed for a cooling tonnage.
Enter your values
ⓘ Live results
Results
- Required airflow
- 1,200 CFM
- Cooling capacity
- 36,000 BTU/h
- Return duct area needed
- 247 sq in at 700 FPM
- In m³/h
- 2,039
Quick answer
Multiply tons by your design CFM per ton — 400 is the standard default.
CFM = tons x CFM per ton
How to use the Tons to CFM Calculator
- 1Enter the nominal tonnage of the system.
- 2Keep 400 CFM/ton unless your climate calls for 350 or 450.
- 3Size the return and supply duct for that airflow.
Worked example
Using the values the calculator loads with:
Inputs
- Cooling capacity3 tons
- Design airflow400 CFM/ton
Results
- Required airflow1,200 CFM
- Cooling capacity36,000 BTU/h
- Return duct area needed247 sq in at 700 FPM
- In m³/h2,039
Frequently asked questions
How much CFM for a 3 ton unit?
About 1,200 CFM at the standard 400 CFM per ton.
What if my ducts cannot carry it?
Undersized duct raises static pressure and cuts capacity; enlarge the return first, it is usually the bottleneck.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.