Carbon Footprint Estimator

Personal carbon footprint is the total greenhouse gas emissions generated directly and indirectly by an individual’s activities, expressed in metric tons of CO₂ equivalent (tCO₂e) per year. “CO₂ equivalent” (CO₂e) accounts for other greenhouse gases (methane, nitrous oxide) by converting them to the warming impact of CO₂ over 100 years.

Total footprint formula: Total CO₂e = Transport + Home Energy + Diet + Flights + Consumer Goods + Services

Transport formula: Car CO₂e = (Annual Miles ÷ MPG) × 8.887 kg CO₂ per gallon of gasoline

Flight formula (economy class): Flight CO₂e = Distance (km) × 0.255 kg CO₂e per km per passenger (Business class: multiply by 2.9× due to larger seat footprint and fewer passengers per plane)

Home energy formula: Energy CO₂e = kWh per year × Grid Emission Factor US average grid: 0.386 kg CO₂ per kWh (varies by state — coal-heavy states up to 0.7 kg/kWh; hydro-heavy states as low as 0.05 kg/kWh)

What each variable means:

• 8.887 kg — the CO₂ produced by burning one US gallon of gasoline (EPA standard)
• Grid emission factor — how much CO₂ your electricity grid produces per kWh; lower for renewable-heavy grids
• Scope 1 vs Scope 3 — Scope 1 = direct (burning gas in your car). Scope 3 = embedded emissions in goods you buy.

Global average carbon footprints (tCO₂e/year, 2024):

• World average: 4.7 tCO₂e
• United States: 14.5 tCO₂e
• European Union: 6.8 tCO₂e
• India: 1.9 tCO₂e
• Climate target (Paris Agreement 2050 goal): 2.0 tCO₂e per person

Worked example: Car: 12,000 miles/year at 28 MPG → (12,000 ÷ 28) × 8.887 = 428.6 × 8.887 = 3,807 kg = 3.81 tCO₂e Home electricity: 9,000 kWh/year × 0.386 = 3,474 kg = 3.47 tCO₂e Diet: Average omnivore diet ≈ 2.5 tCO₂e One round-trip transatlantic flight (10,000 km each way): 20,000 × 0.255 = 5,100 kg = 5.1 tCO₂e

Estimated annual total: 14.88 tCO₂e — just above the US average, driven primarily by the long-haul flight.