1. What is an Air Flow CFM Calculator?

Definition: This calculator determines the volumetric flow rate of air in cubic feet per minute (CFM) based on velocity and cross-sectional area.

Purpose: It helps HVAC professionals, engineers, and technicians calculate air flow for ventilation systems, ductwork design, and air handling applications.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q_{cfm} \) — Air flow rate (cubic feet per minute)
• \( V \) — Air velocity (feet per second)
• \( A \) — Cross-sectional area (square feet)
• 60 — Conversion factor (seconds to minutes)

Explanation: The formula converts velocity in feet per second to volume flow in cubic feet per minute by multiplying by the area and time conversion.

3. Importance of Air Flow Calculation

Details: Proper air flow calculation ensures adequate ventilation, efficient system operation, and compliance with building codes and standards.

4. Using the Calculator

Tips: Measure the air velocity (in ft/s) and the cross-sectional area of the duct or opening (in ft²). Enter both values (must be > 0).

5. Frequently Asked Questions (FAQ)

Q1: How do I measure air velocity?
A: Use an anemometer at several points in the duct and calculate the average velocity.

Q2: What's a typical air velocity for HVAC systems?
A: Residential systems typically operate at 700-900 ft/min (12-15 ft/s), while commercial systems may be higher.

Q3: Does this work for rectangular ducts?
A: Yes, calculate area as width × height (in feet) for rectangular ducts.

Q4: How does temperature affect the calculation?
A: This calculator assumes standard conditions. For precise work, consider air density corrections at different temperatures.

Q5: What's the difference between CFM and ACFM?
A: CFM is cubic feet per minute at actual conditions, while ACFM (actual CFM) accounts for temperature and pressure variations.