Rack Cooling Airflow Calculator
Per-rack CFM for a server cabinet.
Enter your values
Enter the rack power draw in W.
Enter the delta t 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.
- Rack airflow needed
- 790 CFM
- Heat output
- 17,060 BTU/hr
- Tiles at 400 CFM each
- 2
- Watts per CFM
- 6.33
Quick answer
A typical server rack needs roughly 160 CFM per kW at a 20F rise, so a 5kW rack needs about 800 CFM.
CFM = (W x 3.412) / (1.08 x dT)
At a glance
| What it does | Per-rack CFM for a server cabinet. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Rack power draw, Delta T |
| Main output | Rack airflow needed |
| Formula | CFM = (W x 3.412) / (1.08 x dT) |
| Cost | Free — no sign-up, no download |
How to use the Rack Cooling Airflow Calculator
- 1Enter the rack's total power draw in watts.
- 2Choose the allowable delta-T across the rack, commonly 20F.
- 3Match perforated tile or in-row airflow to the result.
Inputs explained
- Rack power draw(W)
- Enter the rack power draw in W.
- Delta T(F)
- Enter the delta t in F.
Worked example
Using the values the calculator loads with:
Inputs
- Rack power draw5000 W
- Delta T20 F
Results
- Rack airflow needed790 CFM
- Heat output17,060 BTU/hr
- Tiles at 400 CFM each2
- Watts per CFM6.33
Frequently asked questions
What if racks vary a lot?
Calculate each rack separately, then balance tiles or dampers to match hot spots.
High density racks?
Above 10kW/rack, in-row or rear-door cooling usually beats raised-floor tiles.
What do I need to enter into the Rack Cooling Airflow Calculator?
Just 2 values: rack power draw, delta t. 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 Rack Cooling Airflow Calculator work out the answer?
A typical server rack needs roughly 160 CFM per kW at a 20F rise, so a 5kW rack needs about 800 CFM. It applies the formula CFM = (W x 3.412) / (1.08 x dT) and shows the working so you can check each step by hand.
Is the Rack Cooling Airflow 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.