How do I choose the right size exhaust fan for my kitchen or bathroom?

Properly sizing an exhaust fan for your kitchen or bathroom is essential for efficient ventilation. Selecting the right size ensures that the fan effectively removes odors, moisture, and pollutants from the room. Here's a comprehensive guide on how to choose the right exhaust fan size:

Understand the Room Volume

Before selecting an exhaust fan, you must understand the volume of the room you want to ventilate. Measure the room's length, width, and height in meters to calculate the cubic meter volume. This measurement represents the room's volume, which is crucial for fan sizing.

Use the Air Changes Per Hour (ACH) Calculation

The next step is to determine the desired number of air changes per hour (ACH). ACH represents how many times the fan should replace the room's air in an hour. For kitchens, aim for 15 to 20 ACH, while bathrooms require 8 to 10 ACH.

Calculate the Required Airflow

To calculate the required airflow (in cubic meters per hour or m³/h), multiply the room's volume by the desired ACH. The formula is:

Required m³/h = Room Volume (m³) x ACH

For example, a 3m x 4m bathroom with a requirement of 8 ACH:

Required m³/h = (3m x 4m x 8) = 96 m³/h

Consider Factors That Impact Sizing

While the ACH calculation is a starting point, consider other factors that may affect sizing:

  • Cooking Style (Kitchens): If you do a lot of frying and heavy cooking, consider a higher m³/h to handle increased moisture and odors.
  • Room Layout: If the room has an open floor plan or connects to other areas, you may need a larger fan to ensure proper ventilation throughout the space.
  • High Ceilings: Rooms with high ceilings require more powerful fans to circulate air effectively.
  • Additional Fixtures: If the room has multiple fixtures like showers or cooktops, the m³/h should account for each source of moisture and odors.

Choose the Right Exhaust Fan

Based on your calculations and considerations, select an exhaust fan with the appropriate m³/h rating. Many fan models provide m³/h information on the packaging. If you're unsure, consult with a professional to ensure you choose the right size for your specific needs.


Choosing the right size exhaust fan is crucial for maintaining indoor air quality in your kitchen and bathroom. Understanding the room's volume, calculating the required m³/h, and considering additional factors will help you make an informed decision. Proper ventilation ensures a healthier and more comfortable living environment.