Method
Each activity is multiplied by its emission factor and summed. The calculator reports metric tons CO2e per year, which makes electricity, gas, driving and flights easier to compare on the same scale.
Example
If a household uses 9,000 kWh of electricity at 0.4 kg CO2e per kWh, that part adds 3,600 kg CO2e. Add 500 therms of gas at 5.3 kg per therm and 8,000 driving miles at 0.4 kg per mile, and the estimate becomes 9,450 kg CO2e before any flight emissions, or 9.45 metric tons per year.
Common mistakes
Use annual activity numbers, not monthly bills, unless you multiply them by 12 first. Replace the default factors when you have local electricity-grid, vehicle or fuel-specific data. Do not mix CO2-only factors with CO2e factors without noting the difference.
Limitations
This is a household activity estimate, not a full lifecycle inventory. It excludes food, goods, services, construction, waste, upstream supply chains and regional policy differences unless you add them separately.
References
- U.S. EPA: Greenhouse Gas Equivalencies Calculator, accessed 2026-05-17.
Last reviewed: 2026-05-17