BTU to CFM Calculator
Airflow from heating or cooling load.
Enter your values
Enter the sensible load in BTU/h.
Enter the temperature difference in °F.
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
- 1,667 CFM
- Equivalent tons
- 3
- At 400 CFM/ton
- 1,200 CFM
- In m³/h
- 2,832
Working
- 136,000 / (1.08 x 20) = 1,667 CFM
Quick answer
For air, sensible BTU/h equals 1.08 times CFM times the temperature difference, so CFM = BTU/h / (1.08 x ΔT).
CFM = BTU/h / (1.08 x ΔT)
At a glance
| What it does | Airflow from heating or cooling load. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Sensible load, Temperature difference |
| Main output | Required airflow |
| Formula | CFM = BTU/h / (1.08 x ΔT) |
| Cost | Free — no sign-up, no download |
How to use the BTU to CFM Calculator
- 1Enter the sensible load in BTU per hour (not total load with latent heat).
- 2Enter the design temperature split — 20 °F cooling, 40–70 °F for furnaces.
- 3Use the airflow to size ducts and blower speed.
Inputs explained
- Sensible load(BTU/h)
- Enter the sensible load in BTU/h.
- Temperature difference(°F)
- Enter the temperature difference in °F.
Worked example
Using the values the calculator loads with:
Inputs
- Sensible load36000 BTU/h
- Temperature difference20 °F
Results
- Required airflow1,667 CFM
- Equivalent tons3
- At 400 CFM/ton1,200 CFM
- In m³/h2,832
- 36,000 / (1.08 x 20) = 1,667 CFM
Frequently asked questions
Where does 1.08 come from?
It bundles air density, specific heat and the 60 minutes per hour into one constant at standard conditions.
Do I use total or sensible BTU?
Sensible only — latent load removes moisture and does not change air temperature.
What do I need to enter into the BTU to CFM Calculator?
Just 2 values: sensible load, temperature difference. 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 BTU to CFM Calculator work out the answer?
For air, sensible BTU/h equals 1.08 times CFM times the temperature difference, so CFM = BTU/h / (1.08 x ΔT). It applies the formula CFM = BTU/h / (1.08 x ΔT) and shows the working so you can check each step by hand.
Is the BTU 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.