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How We Calculate Your Carbon Footprint
This calculator estimates your carbon footprint using the formula: Emissions = Activity Data × Emission Factor. Here’s how we do it for each category:
- Travel: Car emissions use fuel efficiency and type (e.g., 8.8 kg CO2e/gallon gasoline, EPA), public transit (~0.1 kg CO2e/mi, BEIS), and flights (0.15 kg CO2e/mi, ICAO).
- Energy: Electricity varies by region (e.g., 0.5 kg CO2e/kWh USA, IEA), heating/cooling use therms (5.3 kg CO2e/therm, IPCC) or kWh.
- Diet: Diet types use meal-based factors (e.g., 10 kg CO2e/meal high-meat, Poore & Nemecek 2018), dairy (3 kg CO2e/kg), waste (1.4 kg CO2e/kg, EPA).
- Shopping: Items have fixed factors (e.g., 15 kg CO2e/clothing, Carbon Trust), waste adjusted by recycling (0.7 kg CO2e/kg, EPA).
- Digital: Streaming (0.05 kg CO2e/hour), internet (0.02 kg CO2e/hour), charging (region-specific kWh, The Shift Project).
- Extras: Commute/leisure (0.4/0.15 kg CO2e/mi, EPA), offsets (0.02 tons CO2e/tree, Gold Standard).
Sources include the U.S. EPA (epa.gov), IPCC (ipcc-nggip.iges.or.jp), BEIS (gov.uk), IEA (iea.org), and scientific studies like Poore & Nemecek (science.org). Regional factors adjust electricity emissions for accuracy.