What is CFM in Air Handling Unit? & how to calculate it

CFM, or Cubic Feet per Minute, is a vital measurement in HVAC, especially for AHU Supplies, an air handling unit supplier in India, as it quantifies the rate of air movement within systems crucial for designing and maintaining efficient air distribution.

How to Calculate CFM:

The formula for calculating CFM depends on the specific application and requirements of your HVAC system.

Here are some common methods for calculating CFM:

Direct Measurement:

It is the most accurate method and involves using specialized equipment like an anemometer to directly measure the airflow at a specific point within the duct or system. Measurements are in feet per minute, yielding the Specific CFM for that location. Repeat this process at various points in the system to get an overall CFM measurement.

Use of Airflow Sensors:

Modern HVAC systems frequently incorporate airflow sensors for continuous real-time CFM monitoring. These sensors gauge air velocity at different system points and calculate CFM using duct dimensions.

Use of Velocity and Cross-Sectional Area:

When direct measurements are not possible, one can calculate CFM using the air velocity and the cross-sectional area of the duct. This calculation’s formula is:

CFM = Velocity (in feet per minute) × Cross-Sectional Area (in square feet)

Use the formula given below to determine the cross-sectional area:

Area = π × (Diameter/2)^2 for circular ducts


Area = Length × Width for rectangular ducts

Multiply the velocity by the cross-sectional area to obtain the CFM.

Use of Fan Laws:

If you know the RPM (Revolutions Per Minute) of a fan, you can use fan laws to calculate the CFM. The fan laws describe how adjustments in a system result in changes in RPM, static pressure, and CFM. By adjusting fan speed while knowing the initial CFM and RPM, you can calculate the new CFM using fan law equations.

It’s important to note that CFM calculations can become complex in systems with multiple branches, varying duct sizes, and different components. For precise CFM calculations, consult HVAC experts or employ specialized software.

Importance of CFM in AHUs:

CFM is a crucial parameter in AHUs and HVAC systems for several reasons:

Comfort and Indoor Air Quality:

CFM impacts indoor comfort and air quality by controlling the supply of fresh air. Adequate CFM ensures a healthy and comfortable indoor environment through proper ventilation and air exchange.

Energy Efficiency:

Overly high or low CFM can lead to energy wastage. 

Excessive CFM wastes energy, while insufficient CFM leads to inefficient heating or cooling. Optimal CFM ensures energy efficiency.

Equipment Sizing:

CFM requirements guide the sizing of HVAC components like fans, coils, and filters. Undersized or oversized equipment can lead to performance issues and increased operating costs.


Balancing the airflow in an HVAC system to match the design CFM is essential for uniform temperature distribution and preventing issues like hot or cold spots in a building.


Meeting building codes and standards often require adherence to specific CFM requirements, especially in commercial and industrial settings. Proper CFM ensures compliance with regulations.

In the HVAC arena, where the precise control of CFM (Cubic Feet per Minute) is paramount for efficient air movement, Climate Grip stands as a crucial ally. Our advanced technologies bring invaluable enhancements to CFM management. Climate Grip integrates sophisticated sensors and monitoring systems that continuously gauge air velocity and flow throughout HVAC setups, providing real-time CFM data. This constant vigilance ensures that HVAC systems operate optimally, conserving energy and enhancing indoor comfort. It often integrates Smart fan control systems that use precise CFM data to dynamically adjust fan speed and airflow, cutting energy use and operational expenses. Climate Grip is your AHU supplies and air handling unit supplier in India. Specialized HVAC software efficiently calculates CFM for complex configurations, including various duct sizes, components, and adjustments, ensuring system optimization. Climate Grip’s sustainability commitment aligns seamlessly with CFM management. Their solutions optimize airflow to meet energy efficiency standards and building codes, reducing costs and environmental impact. Climate Grip revolutionizes HVAC CFM management, aligning it with sustainability and efficiency needs while enhancing indoor comfort and air quality.


In the HVAC industry, Climate Grip is a trusted AHU Supplies, an Air handling unit supplier in India, offering advanced technologies for precise CFM (Cubic Feet per Minute) control and energy-efficient fan control systems. Climate Grip’s software precisely calculates CFM in intricate HVAC systems, prioritizing sustainability and compliance with energy efficiency standards. It revolutionizes CFM management in HVAC to meet modern demands for sustainability, efficiency, and improved indoor air quality.

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