Room Ventilation Calculator
Calculate required airflow (CFM) from room volume and desired air changes per hour (ACH).
Last reviewed by the Radiatus Cloud team
Output
Need this done properly for your business?
Radiatus delivers secure cloud, DevOps & compliance engineering.
Work out the airflow a room needs
Proper ventilation is measured in airflow, and sizing it means matching the room to a target air change rate. This calculator computes the required airflow in CFM from your room volume and desired air changes per hour.
Why air changes per hour is the target
Ventilation is judged by how often the room’s whole air volume is replaced per hour, the air change rate, and different room uses need different rates, a bathroom or kitchen needs more than a bedroom. The required airflow in CFM is the room volume times the target air changes, divided by the minutes in an hour. Sizing a fan or system to that figure ensures the room is properly ventilated rather than stuffy or, at the other extreme, over-ventilated and wasteful. It turns a comfort question into a concrete airflow number to specify.
A planning estimate
These are estimates from a standard method for general planning, not professional advice; confirm anything important for your specific situation. It runs entirely in your browser, so nothing you enter is uploaded and it works without an account, keeping your data on your own machine.
Related tools
- User Agent Parser — Parse a User-Agent string into browser, engine, operating system and device. Explains why UA strings are unreliable and what to use instead.
- QR Code Generator — Generate QR codes for URLs, text, Wi-Fi and contact details. Adjustable error correction and size, produced entirely in your browser.
- Credit Card Validator — Validate a card number with the Luhn algorithm and identify the issuing network from its prefix. Runs locally, nothing is transmitted.
- Text Case Converter — Convert text between camelCase, PascalCase, snake_case, kebab-case, CONSTANT_CASE, Title Case and sentence case. Runs entirely in your browser.
Frequently Asked Questions
What is an air change per hour?
How many times the room’s entire air volume is replaced in an hour. Different room uses need different rates for comfort and air quality.
How is the required airflow calculated?
As the room volume times the target air changes per hour, converted to CFM (cubic feet per minute), the standard unit for specifying fans.
Why do rooms need different rates?
Because bathrooms and kitchens produce moisture and odours needing more frequent air changes than a bedroom, so the target rate varies by use.
What does the CFM figure let me do?
Specify a fan or ventilation system sized to actually ventilate the room, rather than one too weak to help or needlessly powerful.
Is my data uploaded?
No. The calculation runs entirely in your browser.
Privacy & Security
Calculated locally in your browser. No data is sent to any server.
How to Use
Enter room dimensions and target ACH to estimate required CFM.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
Related Tools
User Agent Parser
UtilityParse a User-Agent string into browser, engine, operating system and device. Explains why UA strings are unreliable and what to use instead.
QR Code Generator
UtilityGenerate QR codes for URLs, text, Wi-Fi and contact details. Adjustable error correction and size, produced entirely in your browser.
Credit Card Validator
UtilityValidate a card number with the Luhn algorithm and identify the issuing network from its prefix. Runs locally, nothing is transmitted.