Airflow Calculator — Calculate Airflow in Ducts and Vents

Airflow Calculator

Calculate airflow in ducts, vents, and HVAC systems. Understand how duct size, velocity, and pressure affect airflow performance.

Step 1: Duct & Airflow Details

Understanding Airflow Calculations

Airflow is calculated using the duct cross-sectional area and air velocity. For round ducts, area = π × (diameter/2)². For rectangular ducts, area = width × height.

Step 2: Additional Options

0.5

About Static Pressure

Static pressure is the resistance to airflow in a duct system. Higher static pressure requires more fan power to maintain the same airflow. Typical residential systems operate at 0.5-0.8 inches of water column.

Airflow Calculation Results

Summary
Duct Comparison
Velocity Analysis

Calculated Airflow

942.5 CFM
Velocity: 800 FPM
Duct Cross-Sectional Area
113.1 in²
Air Velocity
800 FPM
Equivalent Round Diameter
12.0 in
System Category
Residential HVAC

Duct Size Comparison

Duct Size Area Velocity Airflow Pressure Drop

Velocity vs Airflow Analysis

Airflow Calculation Formula

Q = A × V

The airflow (Q) is calculated by multiplying the cross-sectional area (A) of the duct by the air velocity (V). For round ducts, A = π × (d/2)². For rectangular ducts, A = w × h.

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