CFM Calculator (Cubic Feet per Minute)

What is CFM?

CFM (Cubic Feet per Minute) measures the volume of air that moves into or out of a space every minute. It is critical for proper ventilation, thermal comfort, and indoor air quality.

CFM Formula

Formula: CFM = (Room Volume × ACH) ÷ 60

Where:
Room Volume = Length × Width × Height (in cubic feet)
ACH = Air Changes per Hour

Example Calculation

Room 20 × 15 × 10 ft, ACH = 4:
Volume = 20 × 15 × 10 = 3,000 cu.ft
CFM = (3,000 × 4) ÷ 60 = 200 CFM
✅ This means the ventilation system should supply 200 cubic feet of air per minute.

Recommended ACH by Room Type

Room Type	ACH Range
Bedroom	2 – 4
Living Room	4 – 6
Office	6 – 8
Classroom	6 – 20
Kitchen	10 – 15
Hospital Room	6 – 12

Frequently Asked Questions

How is CFM different from ACH?

CFM measures actual airflow per minute, whereas ACH indicates how many times the room air is replaced per hour.

Why is proper CFM important?

It ensures comfortable temperatures, healthy indoor air, and prevents stuffiness or odors.

How do I choose ACH?

Select ACH based on room type and usage. Higher ACH is needed in kitchens, bathrooms, and hospitals.