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Air Changes per Hour (ACH) Calculator

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Calculates the air changes per hour (ACH) in a room, which indicates how many times the total air volume in a room is replaced in one hour. This is crucial for ventilation and air quality assessment.

How To Use

How to use this calculator

Start with your values, or try a preset.

Step 1

Enter Room Length, Room Width, Room Height, and Fan CFM (Cubic Feet per Minute) in the units shown.

Step 2

Read Room Volume and Air Changes per Hour (ACH) in the results panel. Results update as you change the inputs.

Step 3

Choose a preset to load an example, then adjust the values for your situation.

Worked Examples

Example calculations

See the inputs and their calculated results.

Small Bedroom

Room Length: 10 ft; Room Width: 12 ft; Room Height: 8 ft; Fan CFM (Cubic Feet per Minute): 150 CFM

Room Volume: 960 ft³; Air Changes per Hour (ACH): 9.375 ACH

Living Room

Room Length: 20 ft; Room Width: 15 ft; Room Height: 9 ft; Fan CFM (Cubic Feet per Minute): 300 CFM

Room Volume: 2,700 ft³; Air Changes per Hour (ACH): 6.666666667 ACH

Kitchen

Room Length: 12 ft; Room Width: 12 ft; Room Height: 8 ft; Fan CFM (Cubic Feet per Minute): 250 CFM

Room Volume: 1,152 ft³; Air Changes per Hour (ACH): 13.02083333 ACH

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