CO2 Breathing Emission Calculator

Your details

Your body weight in kilograms (metric) or pounds (imperial).
kg
Your height in centimetres (metric) or inches (imperial).
cm
MET (metabolic equivalent of task) is the ratio of your active metabolic rate to your resting rate. Higher MET means more CO2 exhaled.
How many hours per day you typically spend at this activity level. The remaining hours use a resting rate (1.0 MET) to fill out a full 24-hour day.
h
CO2 per hourTypical adult range
41.4g/h

Grams of CO2 exhaled per hour at the chosen activity level

CO2 per day0.84kg/day
CO2 per year306.7kg/yr
Body surface area1.853m^2
Activity MET1.3
CO2 volume per hour21.1L/h
Resting CO2 per hour31.8g/h
g/h (active)41.4
g/h (resting)31.8

You exhale about 41.4 g of CO2 per hour sitting quietly.

  • At sitting quietly, you exhale about 41.4 g of CO2 per hour, driven by your body surface area of 1.85 m².
  • Over a full day (8.0 h active, 16.0 h resting), you exhale roughly 840 g, or 0.840 kg.
  • That scales to about 307 kg per year, though your body recycles the carbon it exhales through the food you eat, so breathing itself is carbon-neutral.
  • Body surface area is the strongest predictor of CO2 output at a given activity level: a larger person exhales more CO2 than a smaller person doing the same activity.

Next stepBreathing CO2 is biogenic and part of the natural carbon cycle. If you want to reduce your carbon footprint, focus on energy, transport, and diet rather than breathing.

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