CO₂ Breathing Emission Calculator
Estimate the mass of CO₂ exhaled by a person at rest or during activity. Adjust breathing rate, tidal volume and the CO₂ fraction in exhaled air to see daily, hourly and annual emissions.
breaths/min
mL
%
Grams of CO₂ exhaled in 24 hours at the given breathing parameters
- 1
Tidal volume in litres
500 mL ÷ 1000 = 0.5 - 2
CO₂ fraction
4 % ÷ 100 = 0.04 - 3
CO₂ per breath
0.5 × 0.04 × 1.965 g/L = 0.0393CO₂ density at standard conditions (0 °C, 1 atm) is 1.965 g/L. - 4
CO₂ per minute
0.0393 g × 15 breaths/min = 0.5895 - 5
CO₂ per day
0.5895 × 60 × 24 = 848.9
How does this calculator work?
CO₂ per breath (g) = (tidal volume in litres) × (exhaled CO₂ fraction) × 1.965 g/L. At 15 breaths/min with a 500 mL tidal volume and 4% CO₂, that is about 0.039 g per breath — roughly 200–250 g per day. Increase breathing rate or tidal volume (as in exercise) to scale the result.
Formula
How this is calculated
Each breath moves a volume of air called the tidal volume (TV) in and out of the lungs. The exhaled air contains roughly 4% CO₂ by volume — much higher than the 0.04% in ambient air — because the body produces CO₂ as a metabolic waste product and releases it across the alveolar membrane.
The mass of CO₂ in each exhalation equals the volume of CO₂ (TV × CO₂ fraction) multiplied by the density of CO₂ gas at standard conditions (approximately 1.965 g/L at 0 °C, 1 atm). Multiplying by breaths per minute and the number of minutes in a day gives the daily emission in grams. Resting adults typically exhale 200–250 g of CO₂ per day; the figure rises substantially during exercise.
This is a physical gas-density model and assumes all exhaled CO₂ is measured at STP. In reality exhaled gas is warm and humid, so the true density is slightly lower (~1.84 g/L at 37 °C). The calculator uses the STP figure as a standard reference; adjust the CO₂ % field for higher-intensity breathing where concentration can rise toward 5%.
Frequently asked questions
A resting adult breathing at about 15 breaths per minute with a tidal volume of 500 mL exhales roughly 200–250 g of CO₂ per day. Exercise increases both breathing rate and tidal volume, raising that figure several-fold.
Exhaled CO₂ is part of the natural carbon cycle — the carbon in it was recently absorbed from the atmosphere by the plants we eat, so it is broadly carbon-neutral. Fossil-fuel combustion adds ancient carbon that was sequestered for millions of years, which is why it drives net atmospheric CO₂ increase while breathing does not.
Cells produce CO₂ via aerobic respiration (C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O). This diffuses into the blood, is transported to the lungs, and is expelled. The result is that exhaled air typically contains 3.5–5% CO₂ compared with only ~0.04% in inhaled ambient air.
TG we-Calculate Editorial Team. (2026). CO₂ Breathing Emission Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/co2-breathing-emission-calculator
TG we-Calculate Editorial Team. "CO₂ Breathing Emission Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/co2-breathing-emission-calculator.
TG we-Calculate Editorial Team, "CO₂ Breathing Emission Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/co2-breathing-emission-calculator
@misc{wecalculate_co2_breathing_emission_calculator, title = {CO₂ Breathing Emission Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/co2-breathing-emission-calculator}}, year = {2026}, note = {TG we-Calculate} }
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