CO2 from Breathing Calculator

• •Use the CO2 from Breathing Calculator when you need accurate results quickly without the risk of manual computation errors or unit conversion mistakes.
• •Use it to verify calculations made by hand or in spreadsheets — an independent check can catch errors before they lead to costly decisions.
• •Use it to explore how changing input parameters affects the output — a quick way to develop intuition and identify the most influential variables.
• •Use it when collaborating with others to ensure everyone is working from the same numbers and applying the same assumptions.

The CO2 from Breathing Calculator is a free, browser-based calculation tool for engineers, students, and technical professionals. Calculate the amount of carbon dioxide produced by human breathing based on activity level and duration. Shows CO2 output in grams and kilograms per hour, day, and year. Provides context for understanding the carbon cycle and human metabolic CO2 production. It implements standard formulas and supports both metric (SI) and imperial unit systems with automatic unit conversion. All calculations are performed instantly in your browser with no data sent to a server. Use this calculator as a quick reference and sanity-check tool during design, analysis, and learning. Always verify results against primary engineering references and applicable standards for any safety-critical application.

The CO2 from Breathing Calculator estimates the carbon dioxide produced by human respiration based on activity level and body weight. An average person at rest exhales approximately 200 grams of CO2 per hour, totaling about 900 grams (nearly 1 kg) per day. This output increases dramatically with physical activity, reaching up to 1.5 kg per hour during intense exercise. While human breathing is part of the natural carbon cycle (the carbon comes from food derived from atmospheric CO2), this calculator provides useful context for understanding metabolic processes and comparing biological CO2 with fossil fuel emissions.

• !Treating human breathing CO2 as contributing to climate change. Respiratory CO2 is part of the natural short-term carbon cycle. The carbon was captured from the atmosphere recently by the food we eat. Fossil fuel emissions are the climate problem because they add ancient stored carbon to the current cycle.
• !Applying the resting rate to all 24 hours. Sleep produces less CO2 than resting, and daily activities produce more. The realistic daily average for a mixed-activity day is about 0.9-1.0 kg, not the 4.8 kg that a pure resting rate would suggest.
• !Comparing breathing CO2 to total carbon footprints without context. While a person exhales about 350 kg CO2/year, the average American's total footprint is about 16,000 kg CO2e/year, mostly from fossil fuels, not breathing.