Air Changes Per Hour Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
100% FreeRuns in your browserBasic
Enter Values
Enter your values and press Calculate to see results.
How to use this calculator
- Enter the airflow (m³/h) and the room volume (m³).
- Read the air changes per hour.
How it works
ACH = airflow ÷ room volume — how many times the room's air is replaced each hour.
Worked example
300 m³/h in a 75 m³ room. = 4 ACH.
Common mistakes
- Mixing units — convert L/s to m³/h (× 3.6) first.
- Using the fan's free-air rating, not the installed airflow.
Frequently asked questions
What ACH should a room have?
It varies: living rooms ~0.5, bathrooms ~6–8, commercial kitchens 15+. Check the relevant standard.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.