What this calculator does
The CO₂ Breathing Emission Calculator estimates how much carbon dioxide a person exhales through normal respiration over a day and over a year. While breathing CO₂ is part of the natural short-term carbon cycle (the carbon comes from food, which ultimately comes from plants absorbing atmospheric CO₂), this tool is useful for biology lessons, physiology curiosity, and ventilation or indoor air-quality estimates.
How to use it
Enter your breaths per minute — a typical resting adult breathes about 12–16 times a minute. Then enter the CO₂ exhaled per breath in grams. A common rough figure is around 1 gram of CO₂ per breath at rest, though this varies with breath volume, metabolism, and activity. The calculator returns CO₂ exhaled per day and scales it up to a yearly figure.
The formula explained
There are 1,440 minutes in a day, so breaths per minute × 1,440 gives total breaths per day. Multiply by the grams of CO₂ per breath to get grams per day, then divide by 1,000 to convert to kilograms:
$$\text{CO}_2\ \left(\tfrac{\text{kg}}{\text{day}}\right) = \frac{\text{Breaths/min} \times 1440 \times \text{CO}_2\text{/breath (g)}}{1000}$$
Worked example
Suppose you breathe 12 times per minute and exhale 1 gram of CO₂ per breath. Breaths per day = \(12 \times 1440 = 17{,}280\). CO₂ per day = \(17{,}280 \times 1 = 17{,}280\text{ g} = 17.28\text{ kg}\). Over a year that is \(17.28 \times 365 \approx 6{,}307\text{ kg}\), or about 6.3 tonnes.
FAQ
Does breathing contribute to climate change? Not net — the carbon you exhale was recently absorbed by plants you (or animals you ate) consumed, so it cycles back. Fossil fuels add new carbon, which is the climate concern.
What is a realistic CO₂-per-breath value? Roughly 0.5–1.5 g at rest depending on tidal volume and metabolism; it rises sharply during exercise.
Why estimate it at all? Useful for sizing room ventilation, CO₂ build-up in sealed spaces, and educational comparisons.
