Ventilation Calculator

About the Ventilation Calculator

The Ventilation Calculator is a professional HVAC tool designed for architects, engineers, HVAC technicians, and building planners to calculate required airflow for proper ventilation in enclosed spaces. It supports both ACH-based (Air Changes per Hour) and occupancy-based calculations, making it essential for maintaining air quality, temperature control, and occupant comfort.

⚡Key Features

•Two calculation modes: ACH-based and occupancy-based
•Support for CFM, m³/h, and L/s units
•Real-time airflow calculation
•Room type presets with recommended ACH values
•Automatic unit conversions

🎯Use Cases

•HVAC system design and sizing
•Building code compliance verification
•Indoor air quality planning
•Commercial kitchen ventilation
•Laboratory and cleanroom design

How to Use the Calculator

1Choose the method: Pick room volume with air changes per hour, or occupancy with airflow per person.
2Enter the room or people: Type the room length, width and height, or the number of people.
3Set the rate: Enter the air changes per hour or L/s per person, or use a room preset.
4Choose the output unit: Select CFM, m³/h or L/s and read the required airflow.

Understanding the Formulas

ACH-Based Formula

CFM = (Room Volume in ft³ × ACH) / 60

This formula calculates airflow based on how many times the entire room air should be replaced per hour.

Occupancy-Based Formula

Airflow = Number of People × Airflow per Person

This formula calculates airflow based on the number of occupants and required fresh air per person.

Example Calculation

Room: 10 ft × 12 ft × 8 ft = 960 ft³

ACH: 6 (office space)

Calculation: (960 × 6) / 60 = 96 CFM

Result: 96 CFM required airflow

Recommended ACH Values by Room Type

Storage Room

Low ventilation needs, minimal occupancy

2 ACH

Residential Room

Living rooms, bedrooms

4 ACH

Office Space

Standard office environment

6 ACH

Kitchen / Bathroom

Residential kitchen or bathroom

8 ACH

Workshop

Light industrial workspace

10 ACH

Laboratory

Research or testing facility

12 ACH

Commercial Kitchen

Restaurant or food service

15 ACH

Unit Conversions

CFM

Cubic Feet per Minute

Common in US HVAC systems

m³/h

Cubic Meters per Hour

Standard metric unit

L/s

Liters per Second

Used in building codes

Conversion Factors

• 1 CFM = 1.699 m³/h
• 1 L/s = 2.118 CFM
• 1 m³/h = 0.589 CFM

Practical Applications

HVAC System Design

Calculate required fan capacity and duct sizing for new HVAC installations or system upgrades.

Building Code Compliance

Verify ventilation meets minimum requirements for health, safety, and building regulations.

Indoor Air Quality

Ensure adequate fresh air supply to maintain healthy CO2 levels and reduce pollutants.

Energy Efficiency

Optimize ventilation rates to balance air quality with heating and cooling costs.

Why Use This Calculator?

✓Instant Results: Real-time calculations as you enter values
✓Multiple Methods: Choose between ACH-based or occupancy-based calculations
✓Unit Flexibility: Work with CFM, m³/h, or L/s
✓Room Presets: Quick access to recommended ACH values
✓Free & Accessible: No registration required

💡Pro Tip

When designing ventilation systems, always consider local building codes and specific requirements for your space type. For commercial kitchens, laboratories, or industrial spaces, consult with HVAC professionals to ensure compliance with safety regulations and optimal performance.

Frequently Asked Questions

How do I calculate ventilation from air changes per hour?

CFM = room volume in cu ft × ACH ÷ 60. A 12 × 15 × 8 ft room (1,440 cu ft) at 6 ACH needs 144 CFM, which is 245 m³/h or 68 L/s.

How much fresh air does each person need?

ASHRAE 62.1 asks for 5 CFM (2.5 L/s) per person plus 0.06 CFM per sq ft for offices. European standard EN 16798-1 suggests about 7–10 L/s per person for good indoor air.

How many air changes does a room need?

Guidelines vary by use: homes about 0.35–1 ACH of fresh air (ASHRAE 62.2 sets a whole-house minimum), offices 4–6, kitchens 8–15 when cooking, bathrooms 6–10, workshops and laboratories 6–12 or more.

How do I convert CFM to m³/h and L/s?

1 CFM = 1.699 m³/h = 0.472 L/s. 100 CFM is 170 m³/h or 47.2 L/s.

Which method should I use?

Occupancy for offices, classrooms and meeting rooms, where people are the main pollution source; air changes for kitchens, bathrooms, workshops and rooms with fumes or moisture. For design, check both and use the larger.

Settings

Room Dimensions & ACH

Room Type Presets