Bathroom fan CFM ranges from 50 CFM for a small bathroom to 200 CFM for a large bathroom.
Having the right size bathroom fan is essential for removing excess humidity that can allow mold to grow. It will also assist in removing common bathroom odors.
What’s here? This page includes a bathroom fan calculator to give you the best exhaust fan size for your purposes. You’ll also find a bathroom fan CFM chart for easy reference.
Terminology tip: Bathroom fans are also called exhaust fans, ventilation fans and extractor fans.
Bathroom Fan CFM Calculator
What size bathroom fan do I need? The answer is right here in this bathroom exhaust fan calculator.
Bathroom Fan CFM Calculator
To use the calculator, simply measure the square feet of your bathroom, usually done by multiplying length in feet times width in feet. Include shower stall and tub enclosure space.
Input the information and check off which fixtures you have, and Voila! You’ll have the right size bathroom fan for your room’s size and fixtures.
Why is the number of fixtures important?
Because each fixture represents the potential for more humidity released into the air.
What does CFM stand for? What is exhaust fan CFM? It is cubic feet per minute, and it refers to the amount of air that the fan moves every 60 seconds.
Bathroom Fan CFM Chart
The larger your bathroom, the more air the exhaust fan needs to move in order to keep the bathroom healthy – without excess humidity and with quick removal of odors.
This handy exhaust fan size chart gives you a good idea what size bathroom fan you need.
| Bathroom Size | Bathroom Size (square feet) | Bathroom Fan CFM |
| 5×7 | 35 sq ft | 50 CFM |
| 5×8 | 40 sq ft | 50 CFM |
| 8×8 | 64 sq ft | 70 CFM |
| 8×10 | 80 sq ft | 80 CFM |
| 10×10 | 100 sq ft | 100 CFM |
| 12×12 | 144 sq ft | 200 CFM |
| 10×15 | 150 sq ft | 200 CFM |
Pro tip: Go up 1 size if the bathroom has a shower, bathtub or jetted tub, aka a Jacuzzi tub. Go up 2 sizes if it has multiple fixtures that might be in use at the same time or within a short period of time.
For example, a 70 CFM bathroom fan is large enough to handle a small or medium bathroom up to about 64 square feet – or 8’ x 8’.
However, if the bathroom also has a shower or tub/jetted tub, you should choose a larger fan – 80 CFM or 100 CFM.
An 80 CFM exhaust fan covers 80 square feet under typical conditions. If you have multiple high-volume fixtures like a shower or steam shower and a jetted tub, then an 80 CFM fan is only useful for about 64 square feet.
What Is The Highest CFM Bathroom Fan?
The highest CFM bathroom fans are 380 CFM. Those fans considered large bathroom exhaust fans start at around 240 CFM.
But choosing the largest CFM bathroom fan isn’t always the right choice. Consider the next section.
Can You Have Too Much CFM In The Bathroom?
Yes, your bathroom fan can be too large. The standard rule is at least 1 CFM per square foot.
Too many CFM in the bathroom have two negative consequences:
1). It will be loud. Bathrooms tend to have hard surfaces – tile floors and shower walls, glass shower doors, vinyl tub surrounds. And noise bounces around rather than being absorbed.
Consequently, when the bath fan CFM is too high, the noise might be uncomfortably loud.
2). You’ll waste energy. As a fan exhausts air, it creates negative pressure. As a result, it pulls air into your home from outside.
In winter, warm indoor air will be replaced with cold outside air.
In summer, you’ll send cooler indoor air outside, only to be replaced by warm, humid outside air.
Some exchange is inevitable. It’s how exhaust fans work. But too much CFM in the bathroom is detrimental.
Fan Size CFM for Small Bathrooms
50 to 70 CFM is the best size bathroom fan for rooms up to about 70 square feet. An 80 CFM fan or 100 CFM fan is a better choice if the room has a shower or jetted tub.
*Never go below 1 CFM per square foot of space. And definitely go larger if the room has multiple fixtures using hot water.
Exhaust Fan CFM for Regular Size Bathrooms
The right size bathroom fan for bathrooms of 70 to 100 square feet is 70 CFM to 150 CFM depending on the size and how many fixtures the bathroom has.
Bathroom Fan CFM for Large Bathrooms
100 to 200 CFM exhaust fans are the right size for bathrooms 10’x10’ and larger.
A general rule is 1 CFM per square foot plus adding 50-100 CFM per fixture.
So, a 10×10 bathroom fan size is 100 CFM with just a toilet. Add a shower or jetted tub, and the CFM should be 150 to 200.
Bathroom Fan for High Ceilings
It depends on the total cubic feet of the room: L x W x H = cubic feet.
A key aspect of bathroom fan sizing is that the fan should change the air every 8 minutes, or about 7-8 times per hour if it were to run non-stop.
Sizing the fan requires knowing the cubic feet of the room, which is length x width x height. Then, the right fan size is one that will move that much air in 7-8 minutes.
For example, an 8’ x 12’ bathroom with 9’ ceilings has 864 cubic feet of air. Divide that number by 8 (8 minutes), and you have 108.
Therefore, the fan should be roughly 100 to 120 CFM – that is, able to move 100 to 120 cubic feet per minute in order to move or exchange 864 cubic feet in 8 minutes.
Low Medium High Fan Settings
Brands like Broan, Nutone, Nautilus, FanTech, Delta and Panasonic make fans with multiple settings. This often requires a more complex – and costlier – switch, but you might find the performance options worth the extra cost.
Example: Let’s say you have a 10’ x 10’ bathroom, or 100 square feet. The minimum fan size is 100 CFM. But it might make sense to buy a larger fan like a 200 CFM fan.
Then, choose the fan speed based on the demand.
Toilet being used: 100 CFM setting.
Shower being used: 150 CFM setting.
Steam shower or jetted tub being used: 200 CFM setting.
Don’t forget to try the Bathroom Fan CFM Calculator above for precisely sizing a bathroom exhaust fan.
Did you know? The US Department of Energy’s Energy Star program certifies bathroom ventilation fans. Find one for your home or ask a contractor about an energy efficient exhaust fan for your bathroom.
Bathroom Fan Noise Levels
When choosing a bathroom fan, it’s easy to focus on CFM and overlook an important factor: noise. After all, there’s nothing more distracting than a fan that sounds like an airplane taking off during your morning shower.
Understanding Sones and Decibels
- Sones: The most common measurement for bathroom fan noise. A rating of 1 sone is roughly comparable to the gentle hum of a refrigerator. The lower the sone rating, the quieter the fan.
- Decibels (dB): A handful of manufacturers list noise in decibels, another standard sound measurement. Fans operating around 50 dB or less are often considered relatively quiet.
Noise Levels to Consider
- 0.3 to 1.2 sones: Whisper-quiet; you might barely notice the fan running.
- 1.5 to 2.5 sones: Generally comfortable for most users.
- 3 sones or more: Noticeably loud, which can be intrusive if the bathroom is used late at night or early in the morning.
Why Fan Noise Matters
- Comfort & Convenience: A quieter fan is more likely to be used consistently, which helps reduce humidity and odor problems over time.
- Peaceful Mornings & Evenings: If your bathroom is near bedrooms or shared living spaces, a noisy fan can disturb others.
- Quality Indicators: Lower sone fans often include higher-quality motors and better insulation, which can mean a longer lifespan and fewer repairs down the road.
Pro Tip: If noise is a top concern, invest in a fan rated under 1.5 sones. While these models can cost a bit more upfront, the reduced noise and higher-quality components are well worth it in the long run.
Smart Features & Humidity Sensors
Modern exhaust fans are becoming more advanced to cater to different household needs. Beyond just clearing out moisture, new technology-packed fans can help you manage the bathroom environment more efficiently and conveniently.
- Built-In Humidity Sensors
- Automatic Detection: These fans sense when humidity spikes (like after a hot shower) and switch on automatically.
- Energy Savings: They shut off when moisture levels return to normal, so you’re not using electricity any longer than necessary.
- Mold & Mildew Prevention: Maintaining lower humidity levels curbs the growth of mold and mildew, extending the life of walls, paint, and grout.
- Motion Sensors
- Hands-Free Operation: The fan activates when you enter the bathroom, which is handy if your hands are full or you simply forget to switch it on.
- Timed Shut-Off: Most models turn off after a preset period of inactivity, ensuring the fan isn’t left running unnecessarily.
- Smart Connectivity
- Wi-Fi & App Control: Adjust settings, check runtime, or change fan speeds right from your phone.
- Voice Assistant Integration: Some newer fans work with Alexa, Google Assistant, or other smart home systems for voice commands.
- Data Tracking: Monitor humidity trends over time to spot potential moisture issues early.
- Additional Perks
- Built-In Bluetooth Speakers: Enjoy music or podcasts while you shower without needing extra gadgets in the bathroom.
- LED Lighting: Some fans include ambient or task lighting, eliminating the need for a separate overhead fixture.
Is the Upgrade Worth It?
These smart features are a personal choice. If you often deal with foggy mirrors, lingering odors, or forget to run the fan, a humidity- or motion-sensing model can be a game-changer. For those who love the convenience of controlling home devices via smartphones or voice assistants, smart connectivity can greatly enhance your bathroom experience.
Common Questions
Below are some frequently asked questions and answers to help you make the best decision about bathroom exhaust fans:
- Q: Do I need a larger fan if I have a jetted tub but only use it occasionally?
A: You can sometimes get by with a smaller fan if the tub is rarely used. However, for the best moisture control, especially if guests or family members may use the tub more often than you anticipate, it’s safer to pick a fan with a higher CFM rating. - Q: Are Energy Star-rated fans really worth the extra cost?
A: Yes. Energy Star-rated fans are typically more efficient, quieter, and often come with better components. The extra cost upfront usually pays off through lower energy bills and fewer replacements. - Q: How long should I run the fan after a shower or bath?
A: A good rule of thumb is 15 to 20 minutes. This helps remove residual moisture, preventing mold growth. If you have a humidity sensor or timer switch, it will handle shutting off automatically. - Q: Is it necessary to vent the fan outside?
A: Absolutely. Venting into an attic or crawlspace can trap moisture and lead to mold or structural damage. Always vent through a wall or roof to the outdoors. - Q: What if my bathroom has a window? Do I still need a fan?
A: In many areas, local building codes allow a window in place of an exhaust fan. However, an exhaust fan is far more reliable and effective at eliminating humidity and odors—especially in cold or rainy climates where you may not want to open a window. - Q: Are there any quick ways to reduce fan noise without replacing the whole unit?
A: Checking for loose screws or a misaligned fan grille can sometimes help. Also, cleaning dust buildup can reduce strain on the fan motor. But if the noise level is inherently high due to design or cheap components, replacing the fan may be your best bet.
