Methodology

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:

1. Input extraction: Our AI parses your natural language description to extract activity type, quantity, distance, duration, and other relevant parameters.
2. Factor selection: Based on the activity type and any regional context, we select the appropriate emission factor from our database.
3. Calculation: Emissions are calculated as: Activity × Emission Factor = kg CO₂e.
4. 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.
5. 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.
• Scope boundaries: We primarily focus on Scope 1 and Scope 2 emissions. Full lifecycle (Scope 3) emissions are estimated for some categories.
• Data currency: Emission factors are updated periodically but may lag behind real-world changes.
• AI interpretation: Natural language processing may occasionally misinterpret ambiguous inputs.

Carbon Offset Quality

We partner with CNaught, which curates a diversified portfolio of carbon credits:

• Avoidance projects: Renewable energy, methane capture, forest protection.
• Removal projects: Reforestation, afforestation, soil carbon, direct air capture.
• Verification: Credits from 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.

Last methodology review: March 2026

Questions?

If you have questions about our methodology, contact us at hello@coffset.org.