You must be aware of the bathroom dimensions before you buy the exhaust fan for your home’s bathroom. But the calculation is simple. You must be aware of the measuring unit for ventilation. It is called CFM – Cubic Feet Minute. It is the amount of air that is charged per minute. It is closely connected to your bathroom dimension. Keep your count as 1SqFt = 1CFM. You will find many exhaust fans with 50 to 110 CFM.