How to Calculate the Right Exhaust Fan Size for Your Bathroom (2026 Guide)
Choosing the correct exhaust fan size is one of the most important task in creating a healthy and comfortable bathroom. An undersized fan cannot remove moisture effectively, while an oversized fan may consume unnecessary energy. In this guide, you'll learn how to calculate the right exhaust fan size, understand CFM (Cubic Feet per Minute), and choose the ideal ventilation solution for your bathroom. We'll also explain when a standard exhaust fan is enough and when an inline duct fan is a better option. What is CFM? CFM (Cubic Feet per Minute) measures how much air an exhaust fan can move in one minute. Choosing the correct CFM ensures that moisture, odours, and stale air are removed effectively, helping prevent mould and improving indoor air quality. How to Calculate Bathroom Exhaust Fan Size? Follow these simple steps: 1. Measure the length of your bathroom. 2. Measure the width of your bathroom. 3. Multiply the length by the width to get the floor area. 4. Choose an exhaust ...