Heat Load CFM Calculator
Ventilation needed to remove a watt or BTU heat load.
Enter your values
Choose one of: Watts, BTU/h.
Enter the heat load in W or BTU/h.
Enter the allowed temperature rise 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.
- Airflow required
- 632 CFM
- Heat load
- 10,236 BTU/h
- In kW
- 3
- Equivalent tons
- 0.85
- In m³/h
- 1,074
Working
- 110,236 / (1.08 x 15) = 632 CFM
Quick answer
Airflow to remove heat equals the load in BTU/h divided by 1.08 times the allowable temperature rise.
CFM = BTU/h / (1.08 x ΔT)
At a glance
| What it does | Ventilation needed to remove a watt or BTU heat load. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Load unit, Heat load, Allowed temperature rise |
| Main output | Airflow required |
| Formula | CFM = BTU/h / (1.08 x ΔT) |
| Cost | Free — no sign-up, no download |
How to use the Heat Load CFM Calculator
- 1Choose watts or BTU/h and enter the total heat load.
- 2Set the temperature rise you can tolerate between intake and exhaust.
- 3Size fans for that airflow with headroom for filters and grilles.
Inputs explained
- Load unit
- Choose one of: Watts, BTU/h.
- Heat load(W or BTU/h)
- Enter the heat load in W or BTU/h.
- Allowed temperature rise(°F)
- Enter the allowed temperature rise in °F.
Worked example
Using the values the calculator loads with:
Inputs
- Load unitWatts
- Heat load3000 W or BTU/h
- Allowed temperature rise15 °F
Results
- Airflow required632 CFM
- Heat load10,236 BTU/h
- In kW3
- Equivalent tons0.85
- In m³/h1,074
- 10,236 / (1.08 x 15) = 632 CFM
Frequently asked questions
Why does a smaller ΔT need more air?
The air can only carry so much heat per degree, so a tighter temperature target demands proportionally more airflow.
Is ventilation enough for a server room?
Only if outdoor air is reliably cooler than your target; otherwise you need mechanical cooling.
What do I need to enter into the Heat Load CFM Calculator?
Just 3 values: load unit, heat load, allowed temperature rise. 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 Heat Load CFM Calculator work out the answer?
Airflow to remove heat equals the load in BTU/h divided by 1.08 times the allowable temperature rise. 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 Heat Load 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.