Indoor CO₂ Level Estimator – Calculate CO₂ Concentration in Any Room

Ensure healthy indoor air quality with our CO₂ Level Estimator. Enter room dimensions, occupancy, and ventilation rate to estimate indoor CO₂ concentration in ppm — helping building managers and homeowners maintain safe and productive environments.

Length

Width

Height

Unit

Number of Occupants

Air Changes per Hour (optional)

Typical: 1-2 ACH (natural), 3-6 ACH (mechanical)

CO₂ Analysis

Enter room details and click Calculate to see CO₂ estimate

CO₂ Level Guidelines

400-600 ppm: Outdoor/fresh air quality
600-800 ppm: Good indoor air quality
800-1000 ppm: Acceptable (ASHRAE standard)
1000-1500 ppm: Poor ventilation, drowsiness
1500-2000 ppm: Unhealthy, headaches likely
2000+ ppm: Dangerous, immediate action needed

Note: This is an estimate based on steady-state conditions. Actual CO2 levels vary with activity level, exact ventilation, and time. Use a CO2 monitor for accurate readings.

How to Use This Indoor CO2 Level Estimator

Enter room dimensions

Input the length, width, and height of your room. Select meters or feet for your measurement system.

Specify occupancy and ventilation

Enter the number of people typically in the room. Add air changes per hour if known, or leave blank for an estimate.

View CO2 estimate and recommendations

Results show estimated CO2 concentration in ppm with health impact assessment and actionable tips.

CO2 Levels and Health Effects Reference

CO2 Level (ppm)	Air Quality	Health Effects	Recommended Action
400-600	Excellent	No effects	Maintain current ventilation
600-800	Good	No significant effects	Acceptable for most spaces
800-1000	Fair	Some may feel drowsy	Consider increasing ventilation
1000-1500	Poor	Drowsiness, poor concentration	Increase ventilation immediately
1500-2000	Very Poor	Headaches, sleepiness	Open windows, reduce occupancy
2000+	Dangerous	Nausea, cognitive impairment	Evacuate and ventilate urgently

Source: ASHRAE Standard 62.1, OSHA, and indoor air quality research

Understanding Indoor CO2 Levels

Where Does Indoor CO2 Come From?

People are the main source of indoor CO2. Each person exhales about 18 liters of CO2 per hour at rest. More people or physical activity increases CO2 production. Outdoor air contains about 420 ppm CO2. Indoor levels rise when ventilation cannot keep up with occupancy.

Why Measure CO2?

CO2 is a proxy for ventilation effectiveness. High CO2 means stale air and potential buildup of other pollutants like viruses, VOCs, and odors. Studies show cognitive function declines when CO2 exceeds 1000 ppm. Schools and offices with good ventilation have better performance and fewer sick days.

How Ventilation Affects CO2

Air changes per hour (ACH) determines how quickly indoor air gets replaced. Natural ventilation (opening windows) typically provides 1-2 ACH. Mechanical HVAC systems can deliver 3-6 ACH. Higher ACH means lower CO2 but also higher energy costs for heating or cooling incoming air.

The Steady-State Formula

This calculator uses: C = Co + (G × N) / (Q × 3600). C is indoor CO2, Co is outdoor CO2 (420 ppm), G is CO2 generation per person (18 L/hour), N is number of occupants, and Q is ventilation rate in m³/hour. This assumes steady conditions — real levels fluctuate with activity and airflow.

Tips for Improving Indoor Air Quality

Monitor CO2 continuously

Install a CO2 monitor with a display. Check levels throughout the day. Many monitors alert when CO2 exceeds 1000 ppm.

Ventilate strategically

Open windows on opposite sides of a room for cross-ventilation. Use exhaust fans in kitchens and bathrooms. Run HVAC fans during occupied hours.

Limit occupancy in small spaces

Reduce the number of people in poorly ventilated rooms. A 20 m² office should have no more than 2-3 people for good air quality.

Consider air purification

HEPA filters remove particles but not CO2. For CO2 reduction, you need ventilation or air exchange. Some systems combine both approaches.

Frequently Asked Questions

What is a safe indoor CO2 level?

ASHRAE recommends keeping indoor CO2 below 1000 ppm for good air quality. Levels between 800-1000 ppm are acceptable but may cause mild drowsiness in some people. Above 1500 ppm, most people experience reduced cognitive function and headaches.

How accurate is this CO2 estimator?

This calculator provides a steady-state estimate assuming constant occupancy and ventilation. Real CO2 levels fluctuate with activity, door openings, and HVAC cycling. For precise measurements, use a calibrated CO2 monitor. This tool is best for planning and rough estimates.

What air changes per hour do I need?

Homes typically need 0.35-0.5 ACH minimum under modern codes. Offices and classrooms benefit from 4-6 ACH. Hospitals and labs require 12+ ACH. Higher ACH improves air quality but increases energy costs. Balance ventilation with efficiency.

Does CO2 monitoring help prevent virus spread?

CO2 is a useful proxy for airborne virus risk. High CO2 means exhaled air is accumulating, which could contain viruses if someone is infected. Keeping CO2 below 800 ppm significantly reduces airborne transmission risk in shared spaces.

How do I lower CO2 in my room?

Open windows to increase fresh air intake. Run exhaust fans or HVAC systems. Reduce the number of people in the room. Take breaks to ventilate between meetings. Install a mechanical ventilation system with heat recovery for year-round fresh air.

Other Free Tools

Search tools