Classroom Ventilation Calculator
Ventilation and filtration for a classroom.
Enter your values
Enter the students you are working with.
Enter the room area in sq ft.
Enter the ceiling height in ft.
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
- 388 CFM
- Equivalent air changes
- 2.87 ACH
- Target 5 ACH total
- 675 CFM
- Portable HEPA gap
- 287 CFM CADR
- Room volume
- 8,100 cu ft
Quick answer
Classrooms are typically designed at 10 CFM per student plus 0.12 CFM per square foot of floor area.
CFM = 10 x students + 0.12 x area
At a glance
| What it does | Ventilation and filtration for a classroom. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Students, Room area, Ceiling height |
| Main output | Outdoor air required |
| Formula | CFM = 10 x students + 0.12 x area |
| Cost | Free — no sign-up, no download |
How to use the Classroom Ventilation Calculator
- 1Enter the design class size and room dimensions.
- 2Compare the outdoor air figure against what the unit ventilator actually delivers.
- 3Close any gap to 5 total air changes with portable HEPA units.
Inputs explained
- Students
- Enter the students you are working with.
- Room area(sq ft)
- Enter the room area in sq ft.
- Ceiling height(ft)
- Enter the ceiling height in ft.
Worked example
Using the values the calculator loads with:
Inputs
- Students28
- Room area900 sq ft
- Ceiling height9 ft
Results
- Outdoor air required388 CFM
- Equivalent air changes2.87 ACH
- Target 5 ACH total675 CFM
- Portable HEPA gap287 CFM CADR
- Room volume8,100 cu ft
Frequently asked questions
Why 5 ACH?
Public health guidance after 2020 converged on 5 equivalent air changes per hour for shared indoor rooms.
Do HEPA units count as outdoor air?
No — they add equivalent clean air but do not dilute CO2.
What do I need to enter into the Classroom Ventilation Calculator?
Just 3 values: students, room area, ceiling height. 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 Classroom Ventilation Calculator work out the answer?
Classrooms are typically designed at 10 CFM per student plus 0.12 CFM per square foot of floor area. It applies the formula CFM = 10 x students + 0.12 x area and shows the working so you can check each step by hand.
Is the Classroom Ventilation 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.