Hot/Cold Aisle Calculator

Design hot/cold aisle containment layout from rack count, power density, and aisle dimensions.

Racks per row

Number of rows

Avg power per rack (kW)

Rack width (inches)

Cold aisle width (ft)

Hot aisle width (ft)

Supply air temp (°F)

Tab to move between fields

Total racks

Total IT load (kW)280

Required airflow (CFM)35,385

Floor area (ft²)560

Cold aisle velocity (FPM)553

Return air temp (°F)89

Power density (W/ft²)500

Containment efficiency (%)85

How to Use This Calculator

Enter the number of racks and average kW per rack.
Set aisle width in feet and containment type (cold aisle vs. hot aisle).
Input CRAC/CRAH unit CFM per ton rating.
Review the CFM required per rack and number of cooling units needed.
Verify cold aisle supply air temperature meets ASHRAE A1-A4 envelope for your equipment.

How the result changes with Racks per row

Racks per row: Number of rack cabinets in each row.
Number of rows: Total rows of racks (pairs face each other across cold aisles).
Avg power per rack (kW): Average IT power draw per rack. Low: 3-5kW, Medium: 7-10kW, High: 15-30kW.
Rack width (inches): Rack cabinet width. Standard 19" rack is typically 24" wide with frame.
Cold aisle width (ft): Width of cold (intake) aisles. ASHRAE recommends minimum 4ft.
Hot aisle width (ft): Width of hot (exhaust) aisles. Can be narrower than cold aisles.
Supply air temp (°F): Chilled supply air temperature entering cold aisles. ASHRAE A1: 64-80°F.

Total racks: Total number of rack positions in the layout.
Total IT load (kW): Combined IT power draw of all racks.
Required airflow (CFM): Total cubic feet per minute of conditioned air needed.
Floor area (ft²): Total raised floor area including racks and aisles.
Cold aisle velocity (FPM): Air velocity in cold aisle. Target: <500 FPM for good containment.
Return air temp (°F): Estimated hot aisle return air temperature.
Power density (W/ft²): IT power per square foot of total floor area.
Containment efficiency (%): Estimated cooling efficiency with containment at this velocity.

Identify Input Parameters
4 parameters
Racks per row = 10, Number of rows = 4, Avg power per rack (kW) = 7, Rack width (inches) = 24 = 7 input(s) provided
Calculate Total racks
Total racks
40 = 40
Calculate Total IT load
Total IT load = totalRacks * avgPowerPerRackKw
280 = 280
Calculate Required airflow
Required airflow = cfmPerRack * totalRacks
35385 = 35385