CFM Calculator
Calculate cubic feet per minute (CFM) from duct dimensions and air velocity, or from room volume and air changes per hour.
Method 1: Duct Size + Velocity
CFM (Duct)
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Duct Area (sq ft)
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Method 2: Room Volume + Air Changes/Hour
CFM (Room)
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Room Volume (cu ft)
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How this was calculated
Duct CFM: CFM = Area (sq ft) x Velocity (ft/min). Round duct area = pi x (D/24)^2. Rectangular = (W x H) / 144.
Room CFM: CFM = (L x W x H x ACH) / 60. Typical ACH: office 4-6, warehouse 6-8, kitchen 15-20, lab 6-12.
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Book a free strategy call →CFM and Air Flow Basics
CFM (cubic feet per minute) measures the volume of air flowing through a duct or space per minute. It is the fundamental unit for HVAC sizing, ventilation design, and industrial air handling. Proper CFM ensures adequate ventilation, comfortable temperatures, and compliance with building codes. For industrial facilities, ASHRAE and OSHA standards specify minimum air change rates. Built by Groundwork Analytics.