Tons to CFM Calculator
Airflow needed for a cooling tonnage.
Enter your values
Enter the cooling capacity in tons.
Enter the design airflow in CFM/ton.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- 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
At a glance
| What it does | Airflow needed for a cooling tonnage. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Cooling capacity, Design airflow |
| Main output | Required airflow |
| Formula | CFM = tons x CFM per ton |
| Cost | Free — no sign-up, no download |
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.
Inputs explained
- Cooling capacity(tons)
- Enter the cooling capacity in tons.
- Design airflow(CFM/ton)
- Enter the design airflow in CFM/ton.
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.
What do I need to enter into the Tons to CFM Calculator?
Just 2 values: cooling capacity, design airflow. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Tons to CFM Calculator work out the answer?
Multiply tons by your design CFM per ton — 400 is the standard default. It applies the formula CFM = tons x CFM per ton and shows the working so you can check each step by hand.
Is the Tons to CFM Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.