How we calculate your carbon footprint and ensure transparency in our estimates.
Overview
Coffset's carbon footprint calculator uses a combination of AI-powered natural language understanding and established emission factor databases. When you describe your activities—flights, drives, energy use, diet, purchases—our system extracts the relevant parameters and applies appropriate emission factors to estimate your CO2 equivalent (CO2e) emissions.
Emission Factors
We use emission factors from authoritative sources including:
- Travel: DEFRA conversion factors for flights (short/medium/long-haul, class), cars (by fuel type and size), trains, buses, and ferries.
- Energy: Grid electricity factors by country (IEA data), natural gas, heating oil, and renewable sources.
- Diet: Emission factors per kg of food type based on lifecycle assessments, distinguishing between plant-based, dairy, and meat products.
- Goods & Services: Estimates based on spend-based emission factors and product category averages.
Calculation Approach
Our calculation follows these steps:
- Input extraction: Our AI parses your natural language description to extract activity type, quantity, distance, duration, and other relevant parameters.
- Factor selection: Based on the activity type and any regional context, we select the appropriate emission factor from our database.
- Calculation: Emissions are calculated as: Activity × Emission Factor = kg CO2e
- Radiative forcing (flights): For aviation, we apply a multiplier to account for non-CO2 effects at altitude (contrails, NOx, etc.), typically a factor of 1.9× as recommended by DEFRA.
- Aggregation: Individual emissions are summed to provide your total footprint for the conversation.
CO2 Equivalent (CO2e)
All emissions are expressed in CO2 equivalent (CO2e), which accounts for the global warming potential (GWP) of different greenhouse gases. We use 100-year GWP values from the IPCC AR6:
- CO2: 1
- Methane (CH4): 27.9
- Nitrous oxide (N2O): 273
Limitations
Our methodology has inherent limitations:
- Generalization: We use average emission factors which may not perfectly match your specific situation (e.g., your exact car model, your local utility mix).
- Scope boundaries: We primarily focus on Scope 1 (direct) and Scope 2 (energy) emissions for personal activities. Full lifecycle (Scope 3) emissions are estimated for some categories.
- Data currency: Emission factors are updated periodically but may lag behind real-world changes in technology and energy mix.
- AI interpretation: Natural language processing may occasionally misinterpret ambiguous inputs.
Carbon Offset Quality
For carbon offsets, we partner with CNaught, which curates a diversified portfolio of carbon credits across multiple project types:
- Avoidance projects: Renewable energy, methane capture, forest protection
- Removal projects: Reforestation, afforestation, soil carbon, direct air capture
- Verification: Credits from registries like Verra (VCS), Gold Standard, American Carbon Registry, and Climate Action Reserve
All credits are retired on your behalf, ensuring they cannot be resold or double-counted.
Data Sources
We draw on the following primary sources:
Updates
We regularly update our emission factors and methodology as new data becomes available. Major updates will be noted here.
Last methodology review: March 2026
Questions?
If you have questions about our methodology or want to report an issue with a calculation, please contact us at [email protected].