1. What is CFM Calculation?

CFM (Cubic Feet per Minute) calculation measures the volume of air flow in ventilation systems. It's calculated by multiplying FPM (Feet per Minute) by the cross-sectional area of the duct or opening.

2. How Does the Calculator Work?

The calculator uses the CFM formula:

Where:

• \( FPM \) — Feet per minute (air velocity)
• \( Cross\ Section \) — Cross-sectional area in square feet
• \( CFM \) — Cubic feet per minute (air flow rate)

Explanation: This formula calculates the volume of air moving through a space per minute based on velocity and cross-sectional area.

3. Importance of CFM Calculation

Details: Accurate CFM calculation is crucial for proper HVAC system design, ventilation requirements, industrial exhaust systems, and ensuring adequate air quality in enclosed spaces.

4. Using the Calculator

Tips: Enter FPM in feet per minute and cross-sectional area in square feet. Both values must be positive numbers for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between CFM and FPM?
A: FPM measures air velocity (speed), while CFM measures air volume flow rate. CFM = FPM × Cross-sectional Area.

Q2: How do I measure cross-sectional area?
A: For rectangular ducts: width × height. For circular ducts: π × (radius)². Convert all measurements to feet before calculating.

Q3: What are typical FPM values in HVAC systems?
A: Typically 500-2000 FPM for supply ducts and 600-900 FPM for return ducts, depending on system requirements.

Q4: Why is CFM important in ventilation?
A: CFM determines how much air is being moved, which is critical for maintaining proper air exchange rates, temperature control, and indoor air quality.

Q5: Can I use this for metric calculations?
A: This calculator uses imperial units. For metric, you would calculate CMS (Cubic Meters per Second) using m/s and m².