1. What is CFM Air Flow Measurement?

Definition: This calculator measures air flow in Cubic Feet per Minute (CFM) using air velocity and cross-sectional area.

Purpose: It helps HVAC professionals, engineers, and technicians determine air flow rates in ducts, vents, and other systems.

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 air velocity is multiplied by the area to get volume per second, then converted to minutes.

3. Importance of CFM Measurement

Details: Proper air flow measurement ensures efficient HVAC system operation, proper ventilation, and energy efficiency.

4. Using the Calculator

Tips: Enter the air velocity in ft/s and cross-sectional area in ft². All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: How do I measure air velocity?
A: Use an anemometer to measure air speed at multiple points in the duct for accuracy.

Q2: What's a typical air velocity in HVAC systems?
A: Residential systems typically range from 300-700 ft/min (5-11.7 ft/s), while commercial systems may be higher.

Q3: How do I calculate duct area?
A: For rectangular ducts: width × height. For circular ducts: π × radius².

Q4: Why multiply by 60?
A: This converts cubic feet per second (velocity × area) to cubic feet per minute (CFM).

Q5: What CFM is needed per room?
A: This depends on room size and purpose, but generally 1 CFM per square foot is a starting point for residential spaces.