THE METHOD
Activity times factor
The UK factors let you work out emissions from activity data such as fuel used, kWh of electricity bought or distance travelled. The answer is in kg of CO2 equivalent.
Compare a tripHOW THE NUMBERS ARE MADE
Activity
times factor.
Nobody weighs the carbon from your train ticket.
Compare a trip
kg CO2eper unit of activity
Footprints are estimated: take something you can measure, such as kWh of electricity or kilometres travelled, and multiply it by a published conversion factor. In the UK those factors come from the government, updated every year.
At a glance
- Measure the activity
- Pick this year's factor
- Multiply, then compare
- The same sum behind every footprint
0.131 kg
kg CO2e per kWh generated, 2025 data
The 2026 methodology lists 0.68697 kg CO2e per kWh generated for 1990 and 0.13096 kg for 2025. The last UK coal power station closed in September 2024.
UK GRID ELECTRICITY
1.7×
Recommended multiplier on aviation CO2
A central estimate for the non-CO2 effects of flying, such as contrails. The government says the value is subject to significant uncertainty.
FLIGHTS
TWO NUMBERS WORTH KNOWING
Factors change,
so footprints do too.
One figure on how the electricity factor has moved,
one on how flights are adjusted.
Source: DESNZ, 2026 Government greenhouse gas conversion factors for company reporting, methodology paper (Table 9 and paragraphs 8.39 to 8.43).
A QUICK TRIP CHECK
Same journey,
different factor.
Pick a way to travel to see its factor per passenger per kilometre. Multiply by the distance and you have the footprint. The bar shows how high the factor is.
Figures are greenhouse gases per passenger per km, from UK government conversion factors as compiled by Our World in Data. Real trips vary with vehicle, load and route.
THE SHORT ANSWER
A footprint is
a multiplication.
Emissions are rarely measured directly.
They are estimated from activity data.
ELECTRICITY
The grid factor moves
The electricity factor is the average emission per kWh from the UK grid. It changes every year with the fuel mix, and has fallen steeply since 1990 as coal power ended.
See the numbers
FLIGHTS
Extra effects at altitude
Contrails and other high-altitude effects are not captured by CO2 alone. The 2026 method suggests an optional 1.7 multiplier on the CO2 part of flight emissions.
Why flights differ
WORKING ONE OUT
Four steps to
a fair estimate.
The same steps work for a household bill, a commute or an office. The government publishes a condensed set of factors recommended for most and new users.
Measure the activity
Use real numbers: kWh from an energy bill, litres of fuel, or kilometres travelled.
Use the right year
A new set of factors is published each year with a report explaining major changes. Use the set for the year you are reporting.
Match the unit
Check the factor's unit matches your data. UK gas bills in kWh are usually on a gross calorific value basis, so the gross factor is the default.
Multiply and compare
Activity times factor gives kg CO2e. Compare options with the same method, not figures from different sources.
WHY FLIGHTS ARE TRICKY
Distance, take-off
and altitude.
Short flights have a higher footprint per kilometre because take-off uses much more energy than cruising. The UK factors also add 8% to straight-line distances to allow for indirect routes, delays and circling.
The standard flight factors cover direct CO2, methane and nitrous oxide only. Separate factors apply the 1.7 multiplier for wider climate effects, and the methodology says it should be applied only to the CO2 part.
Questions
Questions people ask
What is a carbon conversion factor?
A number that turns an activity into emissions, such as kg CO2e per kWh of electricity or per kilometre travelled. The UK government factors are designed to calculate emissions from activity data like fuel used, electricity bought or distance travelled.
What does CO2e mean?
CO2 equivalent. It puts different greenhouse gases, such as methane and nitrous oxide, on one scale so they can be added together with carbon dioxide.
Why does the electricity factor change every year?
It depends on the mix of fuels burned in UK power stations and on imported electricity. The methodology says these changes can be large, and coal use has declined over the past decade.
What are Scope 1, 2 and 3?
Scope 1 is direct emissions from things an organisation owns, like its boilers and vehicles. Scope 2 is from purchased electricity, heat, steam and cooling. Scope 3 covers other indirect sources such as business travel and waste.
Can individuals use the UK factors?
The methodology says the factors allow organisations and individuals to calculate emissions. They are aimed at UK reporting; the government notes other uses are at the user's own risk.
Sources
Where the facts come from
- GOV.UK: UK government conversion factors for company reporting of greenhouse gas emissions
- GOV.UK: Greenhouse gas reporting, conversion factors 2026
- DESNZ: 2026 GHG conversion factors methodology report (PDF)
- Our World in Data: Which form of transport has the smallest carbon footprint?
- GHG Protocol: Corporate Accounting and Reporting Standard
ABOUT THIS NAME
Interested in leasing doodlefactor.com?
doodlefactor.com is part of the DoodleSale portfolio. It isn't in an auction right now, but you can ask about leasing it.