Room Volume and Air Changes Calculator
Works out room volume and how often a fan replaces the air.
Room volume
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Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
In litres — L
Air changes per hour — ACH
Minutes per air change — min
The formula
volume = length × width × height ACH = airflow ÷ volume
Air changes per hour say how many times a room’s air could be replaced in an hour, assuming good mixing.
What to watch out for
Real fans deliver less than their rating once ducting is attached.
Frequently Asked Questions
How many air changes per hour does a room need?
The CFM calculator lists typical figures by room type. Local ventilation rules take priority.