Offsetting a car means paying for one tonne of CO₂e to be reduced or removed elsewhere for each tonne the car emits, and making sure those credits are retired. Unlike a flight, a car’s footprint builds up all year, so most people offset a year of driving at a time. This page is part of our guide to offsetting.
How much CO₂ does a car emit?
Two numbers decide it: how far you drive and how much each kilometre emits. The UK government publishes emission factors for cars by size and fuel type in kg CO₂e per vehicle-kilometreSource 1. Multiply your yearly distance by the factor for your car and you have its yearly emissions.
The table below applies the 2026 factors for an average-size car to 10,000 km a year. The distance is an example, not an average; use your own mileage.
Scrolls sideways to show every column.
| Fuel type | Factor (kg CO₂e/km) | For 10,000 km (kg CO₂e) |
|---|---|---|
| Petrol | 0.16152 | 1,615 |
| Diesel | 0.17265 | 1,727 |
| Hybrid | 0.12961 | 1,296 |
| Plug-in hybrid (fuel + UK grid electricity) | 0.09832 | 983 |
| Battery electric (UK grid electricity + grid losses) | 0.02952 | 295 |
As of Oct 2026 · Source: [1] DESNZ greenhouse gas conversion factors 2026
For a petrol car that is about 1.6 tonnes, so two credits would cover it in full. In the United States, where people drive further, the EPA estimates that a typical passenger vehicle emits about 4.6 tonnes of CO₂ a year, based on about 11,500 miles at 22.2 miles per gallonSource 2.
Matched shop
Buy portfolio credits
- Registry serial numbers
- Retirement certificate
- Project documentation
Petrol, diesel, hybrid or electric?
Fuel type changes the result a lot. On the UK factors, an average battery electric car comes to under a fifth of the emissions per kilometre of an average petrol car, because DESNZ counts no direct emissions for it and only the grid electricity it usesSource 1. That figure depends on the grid: where electricity comes mostly from coal or gas, an electric car’s share is higher.
A plug-in hybrid sits in between, and the real figure depends on how often you charge it. If it mostly runs on fuel, use a figure closer to the hybrid or petrol row.
If you know your fuel use rather than your distance, the same DESNZ set has factors per litre of petrol and diesel, which can be more accurate than an average per kilometreSource 1.
Cut what you can first
The Oxford Offsetting Principles start with reducing your own emissions and treat credits as a complement for what remainsSource 4. For a car, that means:
- Share the car. DESNZ factors are per vehicle, so two people in the car halve each person’s share of the tripSource 1. Our World in Data makes the same point: car-sharing reduces your footprint a lotSource 3.
- Take the train or coach for longer trips. DESNZ puts national rail at about 0.031 kg and a coach at about 0.039 kg CO₂e per passenger-kilometre, against 0.162 kg per kilometre for an average petrol car with one person in itSource 1.
- Drive less and combine trips, and walk or cycle short ones.
- Choose a lower-emission car when you replace it. The table above shows the spread by fuel type.
How to offset a car, step by step
Step 1: Find your yearly distance
Use your odometer readings, service records or MOT history to work out how far you drive in a year.
Step 2: Multiply by an emission factor
Use a factor for your car’s fuel type in kg CO₂e per kilometre or mile to get the yearly emissions.
Step 3: Cut what you can
Drive less, share lifts, take the train or bus for some trips, and consider a lower-emission car when you replace it.
Step 4: Work out how many credits you need
One credit covers one tonne of CO₂e, so round the yearly estimate up to whole credits.
Step 5: Buy from a seller you can check
Choose a seller that names the project, standard and registry before you pay.
Step 6: Confirm the retirement
Look up the serial numbers in the public registry and check the quantity and your name.
One credit represents one tonne of CO₂eSource 5. Our credits calculator rounds your estimate up and shows an estimated cost. If you drive and fly, our carbon footprint calculator adds your car, flights, home energy and food together.
Which credits suit a car?
Any credit that meets the quality checks covers a tonne of CO₂e, whatever the source of the emissions. What matters more is that you can see the project, the standard and the retirement record. Our page on removal vs avoidance credits explains the trade-off between cheaper avoidance credits and removals, and the Oxford Principles recommend shifting toward removals over timeSource 4.
Offsetting one year’s driving is a one-off purchase. If you plan to keep offsetting, set a reminder to update the estimate each year with your new mileage.
Be careful with “carbon neutral driving” offers
Claims: what an offset can and can't say
If a product or service describes your driving as “carbon neutral” because credits are bought on your behalf, look behind the label. US guidance says it is deceptive to claim an offset represents reductions that were required by law, and that sellers should disclose when the reductions won’t happen for two years or moreSource 6. Ask which projects are funded, how many tonnes are retired for your mileage and where the retirement record is.
The same steps apply to other parts of your footprint: see how to offset your home energy and how to offset a flight. Our guide to reducing your carbon footprint covers what to cut first.