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What Is The Right Shower Vent Size? [Considerable Factors]

Want to install a shower vent in your bathroom but don’t know what size to get? It’s a common concern. Well, don’t worry as we’ve got the answer to your question.

How to choose the right shower vent size?

Choosing the right shower vent is actually not that critical. Because you’d only have to consider 2 factors. First of all, consider the area of your bathroom. Then figure out the duct size and shape.

This information is quite little for you to understand the entire part. Read our article for a detailed discussion about shower vent size.

How To Choose The Right Shower Vent Size?

There are a few things to consider to get the right size shower vent. Primarily, the vent should be chosen by its performance, basic features, and styles. Installing a shower vent while retiling a bathroom is a great choice.

There are a few other things to think about while picking the correct size shower vent. The specifications are discussed below-

Area Of The Shower Place

Bathroom exhaust fans are classified by the amount of air they can flow. The unit of measurement for this is CFM (cubic feet per minute). For toilets with a square footage of less than 100 square feet, standard fan sizing applies. 

As a general rule, 1 CFM per square foot of room size is required. To measure the area of your bathroom, you can follow a simple step. You can just multiply the length by the width to get the area. 

Remember one thing! Calculating the area of the shower place is helpful in a lot of ways. Because this measurement also helps to identify how much tile you need.

For a 50 square footage, you would need a fan rated at least 50 CFM. This is not the only thing to think about before buying. 

After measuring the area, it is a good idea to enlarge the fan a bit. Besides, your bathroom may have a Jacuzzi or a separate bedroom or niche. In this case, you might require a number of fans. The minimum allowance of the fan size is 50 CFM. 

For instance, an area of a bathroom with 42 square feet would still need a fan of 50 CFM. But if the fan is less than 42 CFM, it might create flapper noises.

However, some people have a misconception of under-sizing the fan. Because they think this would result in less noise. But this is not right.

Extra tip: While showering, you might want the extra moisture to be eliminated from the air. Use a larger fan in that instance (80-110 CFM). Make sure the restroom door has at least a 5/8” gap underneath it. When the door is closed, it permits fresh air to enter the room.

Duct Size And Shape

When determining the size of the ventilation fan, one factor needs to be considered. That is the size and length of the duct. Most 50 CFM fans can be used with 4 inch round ducts. But when you use a higher CFM fan, the duct size will also increase. 

The size will increase to 5 or 6 inch round pipes. The length of the span, number of accessories, elbows also affects how much air your duct effectively transports.

For different operations and configurations, it is difficult to calculate the correct conduit size. But the instructions that came with the fan describe the requirements. Just make sure that the ducts in the fan installation area have enough space. 

Attempting to force too much air through a duct that’s too small causes the fan to overwork. It will eventually provide insufficient ventilation. Rather, you could just add a vent to the existing ductwork. And this would enable fresh air to enter and remove suffocation.

Your bathroom area might be larger than that of a typical bathroom. For bathrooms larger than 100 square feet, the size of the exhaust fan can be adjusted. It can be adjusted according to the number of fixtures in the room. 

To use this formula for calculations, add the required CFM ratings for all accessories-

  • Shower: 50 CFM
  • Bathtub: 50 CFM
  • Toilet: 50 CFM
  • Jetted tub: 100 CFM

As an example, if your bathroom has a shower and toilet, you require a 100 CFM fan. A bathroom with a jacuzzi, toilet, and shower requires a 200 CFM fan. These are the variations followed for a larger area of the bathroom.

Now, you might struggle to choose the best fan for your large shower place. We’ve got a couple of suggestions for you below-

Product 1
Product 2

These are the products you can easily trust.

These are the specifications that are needed to be followed. As a result, you can choose the right vent for your bathroom.


Question: Can I shower keeping the shower vent turned on?

Answer: Yes, you can do it. In fact, you should turn on your shower vent as soon as you start showering. Also, after you’ve finished bathing, turn on the fan for around 20 minutes. This will help to keep your bathroom dry and mold-free. However, don’t keep it turned on for a long time. Because it would cost you unnecessarily.

Question: Is it okay to smoke in the shower place with the vent turned on?

Answer: When smoking, direct the smoke to nearby vents or open windows. Turn off the shower after smoking. However, turn on the fan for an additional 30 minutes. As a result, the weed smoke might be drawn in by the fan. The final step is to take a shower to get rid of the odor of smoking.

Question: Where does the air from the shower vent go?

Answer: The fan draws air from the bathroom and exhausts it out of a vent. After that, it goes above and behind the ceiling. It works in the same way as a kitchen range hood. It does not, however, evaporate moisture; rather, it moves smoke out. 

Final Words

Now, you know how to choose the right shower vent size! Make sure to consider the mentioned factors and do the calculations properly.

We look forward to helping you with our guide. 

Wishing you all the best in your home improvement!