Estimate annual household emissions from electricity, gas, driving and flights using 2026 UK greenhouse gas conversion factors.
Enter your annual activity
Each activity is multiplied by its selected 2026 emissions factor and converted from kilograms to tonnes of CO₂e.
Scope note: This calculator is an activity-based estimate for the categories entered. It does not include food, purchases, construction, waste, public transport or every upstream emission, so it is not a complete personal or organisational carbon account.
How to use the carbon footprint calculator
- Enter annual electricity and gas consumption from bills or supplier statements.
- Select the main car type and enter annual mileage.
- For petrol or diesel, enter UK miles per gallon. For an electric car, enter miles per kWh.
- Add the total passenger-kilometres flown during the year, including return journeys.
- Select Calculate footprint to see the total and category breakdown.
2026 conversion factors used
The estimate multiplies your activity by conversion factors expressed in kilograms of carbon dioxide equivalent (kg CO₂e). CO₂e combines the warming effect of different greenhouse gases into one measure.
| Activity | Factor used |
|---|---|
| UK grid electricity | 0.13096 kg CO₂e per kWh |
| Natural gas, gross calorific value | 0.18231 kg CO₂e per kWh |
| Petrol, average blend | 2.07500 kg CO₂e per litre |
| Diesel, average blend | 2.58354 kg CO₂e per litre |
| Short-haul economy flight with radiative forcing | 0.12576 kg CO₂e per passenger-km |
| Long-haul economy flight with radiative forcing | 0.11704 kg CO₂e per passenger-km |
How driving emissions are estimated
For petrol and diesel cars, UK mpg is converted into litres used: annual miles × 4.54609 ÷ mpg. Fuel litres are then multiplied by the relevant fuel factor. For an electric car, annual miles are divided by miles per kWh and the electricity use is multiplied by the UK grid electricity factor.
Household total versus per-person result
Electricity and gas are normally recorded for the whole home. The headline therefore shows a household total. The per-person figure divides all entered activities by the number of household members; adjust the entries if some travel belongs to only one person.
Understanding flight emissions
Flight fields use passenger-kilometres, meaning distance travelled by one passenger. The factors include an allowance for radiative forcing, reflecting additional climate effects from aviation at altitude. Cabin class and route can materially change the estimate.
What can reduce the result?
- Improve insulation and heating controls to reduce gas demand.
- Reduce unnecessary mileage, drive efficiently or switch suitable journeys to lower-carbon transport.
- Choose an efficient vehicle and charge an EV when lower-carbon electricity is available.
- Reduce flights or choose economy seating where travel is necessary.
- Track the same categories annually using the same method.
Want to measure a planned reduction? Use our Percentage Calculator to compare your current and target emissions.
Primary source: UK Government greenhouse gas reporting conversion factors 2026 and its published methodology. Government factors are designed primarily for reporting UK activities; other uses remain estimates.
Frequently asked questions
What does CO₂e mean?
Carbon dioxide equivalent combines different greenhouse gases according to their warming effect and expresses them as an equivalent amount of carbon dioxide.
Is this a complete personal carbon footprint?
No. It estimates the household energy, driving and flight activities entered. Food, goods, services, waste and other categories are not included.
Why does the calculator ask for UK mpg?
UK miles per gallon uses an imperial gallon of 4.54609 litres. The calculator converts annual mileage and mpg into fuel litres before applying the petrol or diesel factor.
Are electric cars counted as zero emissions?
No. The calculator estimates electricity used for charging and applies the 2026 UK grid factor. It does not include vehicle manufacture or charging losses.
Why can conversion factors change each year?
Energy sources, vehicle fleets, fuel blends, evidence and calculation methods change. The UK Government therefore publishes an updated factor set annually.