Why carbon calculator numbers differ
Different carbon calculators give different numbers for the same person. This isn't because some are wrong — it's because they draw different system boundaries. A boundary defines what emissions count as "yours." Reasonable people disagree about where to draw it.
How our number compares
| Calculator | Typical result | Boundary | What's included that others miss | What's excluded that others include |
|---|---|---|---|---|
| This calculator | ~14,000–16,000 kg | Household + consumption + per-capita public systems | Government/military/infrastructure per-capita allocation (~1,800 kg) | Financed emissions (hidden behind Advanced toggle) |
| EPA Household Tool | ~8,000–12,000 kg | Direct household energy + transport | — | Food, goods/services, public systems, embodied emissions |
| CoolClimate (UC Berkeley) | ~15,000–20,000 kg | Full consumption-based including EEIO spending | Detailed spending-based goods & services (EEIO model) | Uses older emission factors; may double-count some categories |
| Direct household only | ~6,000–10,000 kg | Scope 1+2 — what you directly burn or buy electricity for | — | Everything upstream: food production, manufacturing, services |
| Full consumption-based | ~18,000–25,000 kg | Everything attributable to your spending, including embodied | Full supply chain emissions for all goods and services | May overcount if using broad EEIO multipliers |
Why the numbers diverge
1. System boundary
The single biggest source of difference. A calculator that only counts your home energy and driving will give a number half the size of one that includes your food, clothing, and share of public infrastructure. Neither is wrong — they answer different questions. Our calculator includes public systems because those emissions exist and someone has to account for them.
2. Emission factors
How many kg of CO₂e per kWh of electricity? Per mile of driving? Per kg of beef? These factors come from different databases (EPA eGRID, IPCC, academic studies) and are updated at different frequencies. A calculator using 2018 grid data will show higher electricity emissions than one using 2022 data, because the grid has gotten cleaner. We use EPA eGRID 2022 data (released January 2024).
3. Allocation method
If your household has two adults and two kids, does each person get 25% of the home energy emissions? Or do adults get more? We divide by household size equally. Some calculators weight by age or income. For food, some calculators assign average American diet to everyone; we let you select your actual diet type.
4. Accounting vs. consumption basis
Production-based accounting counts emissions produced within national borders. Consumption-based accounting counts emissions embedded in what you consume, regardless of where it was produced. If your phone was made in China, production-based accounting assigns those emissions to China; consumption-based assigns them to you. We use a hybrid: direct emissions (energy, transport) plus estimated consumption emissions (food, goods).
Our boundary choices and why
We include per-capita public systems (~1,800 kg) because pretending government and infrastructure emissions don't exist makes personal action look more decisive than it is. If you eliminated your entire personal footprint tomorrow, those shared emissions would persist because they're driven by collective decisions, not individual ones.
We exclude financed emissions by default (available under Advanced) because the methodology is still immature and the attribution problem is genuinely hard. We'd rather show nothing than show a confident-looking number built on shaky math.
We use EPA eGRID subregion rates rather than national averages because your electricity footprint depends heavily on where you live. A New Yorker on a hydro-heavy grid has fundamentally different electricity emissions than a West Virginian on a coal-heavy grid.