Louver Size Calculator

What is a Louver?

A louver is a ventilation device with angled blades that allow air to pass through while blocking rain, debris, and direct sunlight. Louvers are commonly used in:

• HVAC systems (air intake or exhaust)
• Industrial ventilation systems
• Power plants, warehouses, and factories
• Commercial and residential buildings

The size of a louver directly affects airflow capacity, efficiency, and pressure loss. That’s why precise sizing is important.

Why Use a Louver Size Calculator?

Traditionally, calculating louver size involves manual equations, but that can be time-consuming. A calculator automates this process and ensures accuracy.

The Louver Size Calculator takes three key inputs:

1. Required Airflow (CFM – Cubic Feet per Minute):
   The total amount of air that must pass through the louver.
2. Maximum Face Velocity (FPM – Feet per Minute):
   The speed of air moving across the louver face. Lower velocity reduces noise and rain penetration.
3. Free Area Percentage (%):
   The ratio of actual open space in the louver versus its total area. This depends on louver design.

With these inputs, the calculator gives:

• Minimum Required Free Area (sq ft)
• Overall Louver Size (sq ft)
• Recommended Square Dimensions (inches x inches)

How the Calculation Works (In Plain English)

Here’s the simple formula behind the tool:

1. Required Free Area (sq ft): Free Area = Airflow (CFM) ÷ Face Velocity (FPM)
2. Overall Louver Area (sq ft): Overall Area = Free Area ÷ Free Area Ratio
3. Recommended Square Opening (inches): Side Length = √(Overall Area × 144)

Example:

• Required airflow = 5000 CFM
• Max velocity = 500 FPM
• Free area = 50%
• Free area = 5000 ÷ 500 = 10 sq ft
• Overall area = 10 ÷ 0.50 = 20 sq ft
• Square opening = √(20 × 144) ≈ 53.7 inches × 53.7 inches

So, you’d need a louver opening of about 54" × 54".

Benefits of Using a Louver Size Calculator

Accuracy – Prevents under-sizing or oversizing
Efficiency – Saves time on manual calculations
Design Optimization – Ensures proper airflow with minimal resistance
Cost-Effectiveness – Avoids wasted material and space
Professional Standard – Helps engineers meet ASHRAE and AMCA guidelines

Best Practices for Louver Sizing

• Always allow extra clearance for frame mounting.
• Use lower face velocity for rain-prone areas.
• Choose higher free area percentages for better efficiency.
• Cross-check results with manufacturer’s louver performance data.

Try the Industrial Louver Size Calculator

With the interactive calculator, you can quickly enter airflow, velocity, and free area percentage to get the exact dimensions you need. It removes guesswork and ensures your ventilation system works as intended.

Input your numbers, hit “Calculate Dimensions”, and get instant results.