How do I know what size exhaust fan I need?

You may need an exhaust fan in your kitchen or bathroom. Although nowadays people prefer installing chimneys in their kitchen. But for proper ventilation, you should install an exhaust fan in your bathroom. When I purchased my house I decided not to install any windows in the bathroom. It can hamper privacy. So, I installed an exhaust fan because as per the guidelines of the National Electrical Code, if a bathroom doesn't have any window it is mandatory to install an exhaust fan. Let me share with you details about the

exhaust fan size chart. 

When I asked my plumber ‘ how do I know what size exhaust fan I need?’, he told me to focus on a few details. 

1. The thumb rule to understand what size exhaust fan is required, you need 1 CFM per square foot of room area. 

2. To know the square footage you need to multiply the length and width. For example, if the width of the bathroom is 6ft and the height is 9ft then the square footage would be 54. Therefore, the fan should have 54CFM.

Some points to consider for exhaust fan size for room:

1. It is a good idea to oversize the exhaust fan. So instead of 54 CFM, you can go for 60 CFM and install the fan accordingly.

2. You can install more than one fan if you have a jetted tub or separate rooms.

Generally, a fan with 50 CFM will have a 4-inch round duct. The size of the duct increases to 5-6 inches as the size goes higher. This is all I have to say about the exhaust fan size chart. I hope you find this helpful.

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Hello there. I saw your question regarding the exhaust fan size for kitchen on this platform. As I have done the same process and got the right-sized fan installed in my kitchen, let me guide you through two possible methods. 

How to Measure Exhaust Fan Size?

Here are the different methods through which you can calculate the required exhaust fan size for a kitchen.

1. The first process revolves around the determination of the fan size of the range hood. The general rule is that the fan should be able to move at least 100 Cubic Feet per Minute (CFM) of air for every 12” of the width of your stove. The formula for the same =

   100/12 x Stove Width

   . Once you have calculated the minimum size for your range hood in CFM, calculate the number with 1728 to know the calculation in cubic inches.

2. The second method will require you to calculate the room size. The larger the space, the larger the fan needed. On average, an exhaust fan should be able to exchange air a minimum of 15 times every 60 minutes.

• To calculate the size, first find out the space of your room by calculating the length, width and height of the kitchen in cubic feet. Now multiply the three to find the kitchen space.

• Next, multiply the obtained kitchen space by 15 to find out the cubic feet of air moved every hour.

• Divide this figure by 60 to obtain the range hood size in CFM.

Hopefully, this helps you learn how to measure exhaust fan size in inches.