CO2 in Room Calculator
Estimate CO2 levels in a room based on volume, occupants, and ventilation rate.
Check if your indoor air quality is healthy.
CO₂ concentration in a room rises when people breathe and falls when fresh air is supplied. Measuring and managing indoor CO₂ levels directly affects cognitive performance, alertness, and health — making it critical for offices, classrooms, and sleeping spaces.
CO₂ accumulation formula: ΔCO₂ (ppm) = (Occupants × CO₂ Generation Rate × Time) / Room Volume × 1,000,000
CO₂ generation rates per person:
- Resting / sleeping: 0.004 L/min
- Seated work / light activity: 0.007–0.010 L/min
- Standing / light exercise: 0.015–0.025 L/min
- Vigorous exercise: 0.040–0.060 L/min
Room CO₂ level formula (with ventilation): Steady-State CO₂ = Outdoor CO₂ + (Occupants × Generation Rate) / Ventilation Rate
Where Ventilation Rate = air changes per hour (ACH) × Room Volume.
CO₂ thresholds and effects:
| CO₂ Level (ppm) | Classification | Effect |
|---|---|---|
| 400–600 | Outdoor / fresh air baseline | Optimal cognitive performance |
| 600–1,000 | Acceptable (ASHRAE standard) | Minor drowsiness in some people |
| 1,000–1,500 | Elevated | Measurable decline in decision-making (Harvard study: ~15% impairment) |
| 1,500–2,500 | High | Headaches, fatigue, difficulty concentrating |
| 2,500–5,000 | Very high | Significant cognitive impairment, possible nausea |
| > 5,000 | Dangerous | Workplace limit; oxygen displacement risk |
Worked example: Conference room: 6 m × 5 m × 3 m = 90 m³. 8 people seated. No ventilation. Outdoor CO₂: 420 ppm. Generation per person: 0.009 L/min = 0.000009 m³/min. After 60 minutes: ΔCO₂ = (8 × 0.000009 × 60) / 90 × 1,000,000 = 0.00432 / 90 × 1,000,000 = 48 ppm × 60 min = 288 ppm rise
Starting at 420 ppm + 288 ppm = 708 ppm — within acceptable range. But without ventilation after 2 hours: ~996 ppm, approaching the performance-impairment threshold.
Solution: Open a window (adds ~3 ACH natural ventilation) to stabilize below 800 ppm throughout the meeting.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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