{"id":4940,"date":"2021-12-22T11:25:08","date_gmt":"2021-12-22T11:25:08","guid":{"rendered":"https:\/\/scottsbathrooms.com\/?p=4940"},"modified":"2022-04-03T13:48:24","modified_gmt":"2022-04-03T13:48:24","slug":"bathroom-exhaust-fan-sizing-chart","status":"publish","type":"post","link":"https:\/\/scottsbathrooms.com\/bathroom-exhaust-fan-sizing-chart\/","title":{"rendered":"Bathroom Exhaust Fan Sizing Chart For CFM (How To Measure?)"},"content":{"rendered":"

When shopping for a bathroom exhaust fan, the last thing you want is to end up with a model that is too weak or too powerful for your needs.<\/p>\n

An inefficient exhaust fan simply won\u2019t be able to remove the excess humidity and stale air from your bathroom. Conversely, an overly powerful model can be needlessly loud and also take an unnecessary toll on your budget.<\/p>\n

If you\u2019d like to avoid finding yourself in situations such as these, it\u2019s vital that you correctly size your new bathroom fan. The following bathroom exhaust fan sizing chart will help you do exactly that:<\/p>\n

What is CFM?<\/h2>\n

When we\u2019re talking about the \u201csize\u201d of these appliances, we\u2019re not talking about their physical dimensions. Instead, we\u2019re referring to their CFM ratings. If you\u2019ve never heard of this term before, it stands for cubic feet per minute and the job of this rating is to tell you how much air a particular bathroom exhaust fan can move during one minute. Most models have a CFM rating of between 50 and 130, although very powerful, 200 CFM-rated units are also available.<\/p>\n

Calculating the necessary CFM rating for your bathroom can be done in a couple of different ways. However, it should be pointed out that all of these methods aim for about 8 air changes every 60 minutes. In other words, all air inside a bathroom needs to be completely replaced at least 8 times during one hour.<\/p>\n

Another thing worth mentioning is that the door of the bathroom really needs to have an adequate gap on the bottom. If this gap doesn\u2019t measure at least five eights (\u215d) of an inch, the exhaust fan is going to have a really hard time properly ventilating the bathroom due to the lack of sufficient makeup air.<\/p>\n

4 Methods of Sizing a Bathroom Exhaust Fan<\/h2>\n

\"Man<\/p>\n

A bathroom exhaust fan can be sized in 4 different ways. These calculations are based on the ceiling height, floor area, as well as extra spaces such as shower or toilet. Here\u2019s a short but comprehensive breakdown of each of these methods in the form of a chart:<\/p>\n

 <\/p>\n\n\n\n\n\n\n\n
CFM Calculation<\/strong><\/td>\nMinimum CFM<\/strong><\/td>\n<\/tr>\n
Large bathrooms (more than 100 square feet)<\/td>\nAdd together every fixture:<\/p>\n

100 CFM – Jacuzzi tub<\/p>\n

50 CFM – Bathtub<\/p>\n

50 CFM – Shower<\/p>\n

50 CFM – Toilet<\/td>\n<\/tr>\n

Regular-sized bathrooms (less than 100 square feet)<\/td>\n1 CFM per square foot<\/td>\n<\/tr>\n
Tall-ceiling bathrooms<\/td>\n\n
    \n
  • Multiply the floor area of the bathroom by its ceiling height<\/li>\n
  • Divide by 60<\/li>\n
  • Multiply by 8<\/li>\n<\/ul>\n<\/td>\n<\/tr>\n
Enclosed areas<\/td>\n50 CFM (one more bathroom exhaust fan)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n

Now, let\u2019s go over each one of these calculations in more detail:<\/p>\n

#1 – CFM Calculation for Large Bathrooms<\/h3>\n

Do you have a bathroom whose square footage is well over 100? If that\u2019s the case, it is recommended that you, instead of using the bathroom\u2019s floor area for the calculation, base the CFM rating on the number of plumbing fixtures inside your bathroom.<\/p>\n

This is very easy when it comes to bathtubs, showers, or toilets – you just have to assign 50 CFM to each of these fixtures. For jacuzzi tubs, you will have to add 100 CFM. So, to recap:<\/p>\n