Ventilation Calculator
Calculate a room's ventilation need (m³/h and L/s) from volume and air change rate.
100 m³/h
Airflow need
| Volume | 50.0 m³ |
| Airflow | 100 m³/h |
| Litres per second | 27.8 l/s |
The ventilation calculator works out how much airflow a room needs for adequate ventilation. Enter the area, ceiling height and air change rate, and you get the required airflow both in cubic metres per hour and litres per second.
How the calculator works and what it’s for▾
How the airflow is calculated
The calculator first works out the room volume by multiplying the area by the ceiling height. It then multiplies that volume by the air change rate, which tells you how many times per hour the room's entire air content is replaced.
The result is also converted to litres per second, the unit often used in ventilation design. The conversion is based on the relationship 1 m³/h = 0.278 L/s.
What you enter and what you get
You enter the room area in square metres, the ceiling height in metres and the desired air change rate in units of 1/h.
The result shows the volume, the required airflow in cubic metres per hour and the same value in litres per second.
Choosing the right air change rate
For homes a common guideline is around 0.5 1/h, meaning half the room's air is replaced each hour. Wet rooms and kitchens need a higher rate to remove moisture and odours.
Pick the rate to match how the space is used: a bedroom is fine with a modest value, while a damp room needs more effective ventilation.
What the calculator is for
The calculator helps you gauge the rough capacity needed from a ventilation unit or extractor fan, for example when planning ventilation during a renovation or for a cabin.
Exact ventilation sizing always requires whole-building design and compliance with regulations, so treat the result as an indicative estimate.
🔄 Reviewed June 2026
Frequently asked questions
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