What is CFM?

Short for cubic feet per minute, CFM measures the volumn of air moved within a minute. It indicates how much air flows through a space or is pushed by a fan, blower, HVAC system. A higher CFM means more air being moved, which is important for tasks that need strong airflow.

CFM = Velocity (feet per minute) x Area (square feet)

How much CFM do you need?

Total Cubic Feet (volume of air) in the room / Target Air Exchange rate for your application from the chart below.

For general HVAC purposes, the typical recommendation is approximately 1 CFM per square foot of floor area. However, this can vary depending on your specific needs, like room occupancy or the presence of certain appliances.

Use the Target Air Exchange Table below to determine what you may need.

Note: this calculator is not intended to be used to calculate for air circulation or HVLS fans. If you have any questions regarding CFM’s, air exchanges needed, the calculator, or which exhaust and or supply fans may be right for your building, please call us at 866-727-1060

Targeted air exchange chart

This Exhaust & Intake Air Ventilation guide is based on 0’ Static Pressure

Why is CFM important?

Calculating the CFM airflow in a room is crucial for maintaining proper ventilation, temperature control, and overall air quality. It ensures that the HVAC system effectively circulates air, delivering heating or cooling as needed, and removing stale or contaminated air. Proper CFM calculation helps avoid issues like inadquate heating or cooling, uneven temperatures, and poor air quality.

• Ventilation: CFM determines how effectively a room’s air is replaced with fresh air, which is essential for removing pollutants, odors, and moisture.
• Temperature Control: Adequate CFM ensures that the HVAC system can distribute conditioned air evenly throughout the space, maintaining comfortable temperatures.
• HVAC System Sizing: Knowning the required CFM helps in selecting the appropriate size and capacity of HVAC equipment, such as air conditioners, furnaces, and fans
• Energy Efficiency: An appropriately sized HVAC system with the right CFM avoids overworking or short cycling, leading to energy savings and reduced operating costs. Excessive CFM can cause draftiness, increased energy costs, and ineffective humidity control. It’s essential to match the CFM to a room’s size and purpose to ensure comfort and optimal efficiency.
• Air Quality: CFM is directly linked to the number of air changes per hour (ACH), which is key indicator of indoor air quality. Proper ACH helps remove contaminations and maintain a healthy environment.
• Preventing Issues: By calculating CFM, you can avoid common HVAC problems like stal or stuffy rooms, uneven temperatures, excessive energy consumption and equipment wear & tear.

Learn basic fan circulation formulas

This practical math formula goes a long way when you’re considering air ventilation improvement in an indoor space:

CFM = (fpm * area)

CFM (Cubic Feet per Minute) is calculated by multiplying the velocity (Feet per Minute) with the area (Square Feet).

CFM / Target Air Exchange Rate

Example CFM Calculation:

Question: I have a warehouse that I want to exhaust hot, stale air from and replace with fresh air. How much CFM will I need?

Answer: The first step is to measure the dimensions of your space, including the height of your ceilings. Once you have those numbers, you want to decide how many air exchanges are needed for that setting. Use our quick use Target Air Exchange Table to find this number. For example, warehouses typically require air exchanges every 7 minutes to notice a difference in air quality. With your space being 25’ L x 50’ W x 75’ H, we would recommend somewhere between 14,000 to 15,000 CFM.

Can CFM be too high for a room?

Yes, CFM can be too high for a room. Excessive CFM can cause draftiness, increased energy costs, and ineffective humidity control. It’s essential to match the CFM to a room’s size and purpose to ensure comfort and optimal system efficiency.