Ventilation / ACH Calculator
Static · formula-only · worked example computed when this page was built · no live data
The Ventilation / ACH Calculator finds the required air changes per hour and supply airflow for a room from its function, area, and occupancy. Example: for a 150 m² office with 25 people and a 3.5 m ceiling, Required ACH = 6 /h, Supply airflow = 3150 m³/h, Supply airflow (CFM) = 1854 CFM (per ASHRAE 62.1:2022 Ventilation Rate Procedure).
How it works
Computed from your inputs per ASHRAE 62.1:2022 Ventilation Rate Procedure. Anything the worked example does not state uses this calculator's standard default; the interactive version shows every input and lets you change it.
Worked example (HVAC & Cooling)
Inputs: a 150 m² office with 25 people and a 3.5 m ceiling.
| Result | Value |
|---|---|
| Required ACH | 6 /h |
| Supply airflow | 3150 m³/h |
| Supply airflow (CFM) | 1854 CFM |
Computed by WorkHive's calculation engine when this page was built; standard: ASHRAE 62.1:2022 Ventilation Rate Procedure.
How to use this calculator
- Read the worked example. It uses a 150 m² office with 25 people and a 3.5 m ceiling and shows every number in the method.
- Follow the formula with your own figures: it returns Required ACH, Supply airflow, Supply airflow, computed per ASHRAE 62.1:2022 Ventilation Rate Procedure.
- To compute interactively, open the Ventilation / ACH Calculator inside WorkHive's free Engineering Design suite (link below). It runs the same method with your inputs.
FAQ
What is an air changes per hour ventilation calculator?
The Ventilation / ACH Calculator is a free online tool that finds the required air changes per hour and supply airflow for a room from its function, area, and occupancy. It shows the formula and a fully worked example so you can check the method, not just the number.
How is it calculated?
The result is computed from your inputs following ASHRAE 62.1:2022 Ventilation Rate Procedure. The worked example on this page shows a real computation with real numbers.
Is the calculator free?
Yes. WorkHive is free: this worked example is open to everyone, and the interactive calculator runs inside the free Engineering Design suite after a free sign-up (your work is saved to your account). WorkHive is a free, offline-first maintenance platform built for Philippine industrial plants.
Run it on your own numbers
Open the interactive Ventilation / ACH Calculator in WorkHive. Free, and a free sign-up saves your calculations, BOMs and scope-of-works to your account.