Our calculators are built on trusted, official data and 20+ years of expertise. Here's exactly how the numbers are worked out — plus answers to the questions we're asked most.
Every result is built on recognised standards and continuously maintained emissions data.
We apply the correct emissions factors for your country's energy grid and transport, so results reflect where you actually are.
Aligned with DEFRA conversion factors and the GHG Protocol — the recognised basis for credible carbon accounting.
Backed by our CaDI database of 50,000+ carbon records, maintained by our experts and updated as factors change.
We use the energy consumption data you provide (kWh of electricity, gas, coal, etc.) and multiply it by the specific carbon ratio for your country's energy grid. The "Number of People" setting splits the total household footprint by the number of residents, giving a "per person" result to compare against national averages.
We calculate the "Great Circle" distance between airports, then apply an emissions factor based on the flight length (short, medium or long haul) and class of travel. We also include Radiative Forcing (RF) to account for the extra impact of emitting at high altitude (contrails and ozone) — approximately 1.9× standard CO2.
We offer three levels of accuracy: Year/Make/Model (most accurate — official manufacturer efficiency data); Mileage & MPG (your specific fuel efficiency); and Distance only (a national average for your vehicle type).
Calculations use national average factors for public transport per passenger-kilometre, accounting for the average occupancy of trains and buses in your region.
This measures the carbon embedded in the things you buy (clothes, food, insurance, IT) and is often a significant part of your footprint. We use "Spend-Based Analysis", drawing on standard industrial input-output tables to estimate emissions per £/$ spent across categories.
Your result is your total CO2 equivalent (CO2e) emissions in metric tonnes. We compare it against the national average and a global "World Target" for context. Our Net Zero Standard helps plot a course to that target.
Whether you're an individual offsetting a flight or an organisation taking responsibility for its emissions, we have the tools to help.