Fresh Air CFM per Person Calculator
Outdoor air rate for occupied spaces.
Enter your values
Enter the occupants you are working with.
Enter the floor area in sq ft.
Choose one of: Office (5 + 0.06), Classroom (10 + 0.12), Retail (7.5 + 0.12), Gym (20 + 0.06), Dining (7.5 + 0.18).
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Outdoor air required
- 190 CFM
- Per person
- 9.5 CFM
- Per square foot
- 0.127
- In L/s
- 90
Working
- 15 x 20 + 0.06 x 1,500 = 190 CFM
Quick answer
Outdoor air is the sum of a per-person rate and a per-square-foot rate for the space type.
Vbz = Rp x people + Ra x area
At a glance
| What it does | Outdoor air rate for occupied spaces. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Occupants, Floor area, Space type |
| Main output | Outdoor air required |
| Formula | Vbz = Rp x people + Ra x area |
| Cost | Free — no sign-up, no download |
How to use the Fresh Air CFM per Person Calculator
- 1Count design occupancy, not the number of desks.
- 2Enter the floor area served by the same air handler.
- 3Divide by the ventilation efficiency if you use a single-zone economiser.
Inputs explained
- Occupants
- Enter the occupants you are working with.
- Floor area(sq ft)
- Enter the floor area in sq ft.
- Space type
- Choose one of: Office (5 + 0.06), Classroom (10 + 0.12), Retail (7.5 + 0.12), Gym (20 + 0.06), Dining (7.5 + 0.18).
Worked example
Using the values the calculator loads with:
Inputs
- Occupants20
- Floor area1500 sq ft
- Space typeOffice (5 + 0.06)
Results
- Outdoor air required190 CFM
- Per person9.5 CFM
- Per square foot0.127
- In L/s90
- 5 x 20 + 0.06 x 1,500 = 190 CFM
Frequently asked questions
Does CO2 control replace this?
Demand control can modulate down to the area component, but the design value still governs equipment size.
Why per area too?
Building materials and furnishings off-gas regardless of occupancy.
What do I need to enter into the Fresh Air CFM per Person Calculator?
Just 3 values: occupants, floor area, space type. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Fresh Air CFM per Person Calculator work out the answer?
Outdoor air is the sum of a per-person rate and a per-square-foot rate for the space type. It applies the formula Vbz = Rp x people + Ra x area and shows the working so you can check each step by hand.
Is the Fresh Air CFM per Person Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.