CFM Calculation for HVAC Devices: Free Calculator & Formulas
Choose the wrong fan and you will feel it every day — a bathroom that stays damp, a kitchen full of lingering smells, a stuffy office, or an air conditioner that runs forever and never quite cools. The number that prevents all of this is CFM — cubic feet per minute, the amount of air a device moves. This guide explains exactly how to calculate CFM for exhaust fans, duct and inline fans, air conditioners, kitchen hoods and whole-house ventilation , and gives you a free multi-mode CFM calculator (validated against ASHRAE and SMACNA references) to size any device in seconds. Figure 1. CFM measures how much air a device moves each minute. The same idea sizes an exhaust fan, an inline duct fan, an air conditioner blower or a kitchen hood — only the required rate changes. Table of Contents The CFM Calculator (5 Modes) What Is CFM? The 3 Core CFM Formulas Recommended Air Changes per Hour (ACH) CFM by Device Type Static Pressure: Why Real CFM...