CRAC Unit Sizing Calculator
Precision cooling capacity and redundancy.
Enter your values
Enter the it load in kW.
Enter the room area in sq ft.
Enter the people you are working with.
Choose one of: N (no spare), N+1, 2N.
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.
- Total heat load
- 85.3 kW
- In tons
- 24.3
- Units required
- 2 (N1)
- Capacity per unit
- 85.3 kW
- Airflow at 20°F rise
- 13,477 CFM
Quick answer
CRAC sizing totals IT load plus lighting, people and envelope gains, then adds redundancy.
total kW = IT + lighting + people + envelope
At a glance
| What it does | Precision cooling capacity and redundancy. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | IT load, Room area, People, Redundancy |
| Main output | Total heat load |
| Formula | total kW = IT + lighting + people + envelope |
| Cost | Free — no sign-up, no download |
How to use the CRAC Unit Sizing Calculator
- 1Enter measured IT load from the PDUs, not nameplate ratings.
- 2Add room area so lighting and envelope gains are included.
- 3Choose the redundancy level your uptime target requires.
Inputs explained
- IT load(kW)
- Enter the it load in kW.
- Room area(sq ft)
- Enter the room area in sq ft.
- People
- Enter the people you are working with.
- Redundancy
- Choose one of: N (no spare), N+1, 2N.
Worked example
Using the values the calculator loads with:
Inputs
- IT load40 kW
- Room area1200 sq ft
- People2
- RedundancyN+1
Results
- Total heat load85.3 kW
- In tons24.3
- Units required2 (N1)
- Capacity per unit85.3 kW
- Airflow at 20°F rise13,477 CFM
Frequently asked questions
Why not use nameplate?
Servers typically draw 40-60% of nameplate, so nameplate sizing wildly oversizes the plant.
N+1 vs 2N?
N+1 covers a single failure or maintenance; 2N gives fully independent paths for tier 3/4 designs.
What do I need to enter into the CRAC Unit Sizing Calculator?
Just 4 values: it load, room area, people, redundancy. 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 CRAC Unit Sizing Calculator work out the answer?
CRAC sizing totals IT load plus lighting, people and envelope gains, then adds redundancy. It applies the formula total kW = IT + lighting + people + envelope and shows the working so you can check each step by hand.
Is the CRAC Unit Sizing 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.