Two quick ventilation answers in one place. Convert between air changes per hour and airflow for any room, or work out how much outdoor air a space needs from the number of people and its floor area, using typical per-person and per-area rates for common space types.
How to use it
- For air changes, enter the room dimensions and either the ACH or the airflow.
- For outdoor air, choose the space type; typical per-person and per-area rates and an occupant density are filled in.
- Type the real number of people if you know it.
- Treat the result as the breathing-zone requirement, then check your local regulations and the air distribution effectiveness.
Step-by-step guides
- Cooling Load Calculation Basics: Solar, Internal and Latent Loads
- Duct Sizing Guide: Equal Friction, Fittings and the Index Run
- Psychrometric Chart for AHU Design: Mixing, Coils and Reheat
More free tools
- Duct Size Calculator — Round & Rectangular Ducts
- MEP Unit Converter — kW, BTU/h, TR, CFM, L/s, bar, psi
- All free MEP calculators
- MEP Library
Results are for preliminary design and checking. Always confirm against the standard edition and local regulations that apply to your project.
Online course · certificate included
HVAC Systems Design — Heating, Cooling & Ventilation
28 modules from heat loss to plant room: boilers, heat pumps, cooling loads, psychrometrics, AHUs and ductwork. The VRF course is included.
Modules 1–3 are free, no account needed · full course €15,00 one-time