Journey CO2 calculator
Rough tailpipe CO2 for one trip: enter distance and economy ( miles + UK MPG or km + L/100 km), then choose petrol or diesel.
Related: MPG to miles per litre, Fuel Trip Calculator.
Estimate tailpipe CO₂ for a single journey from how far you drove and how thirsty the car is. We use standard kg CO₂ per litre for petrol or diesel — combustion only, not fuel production or manufacturing.
Estimated for this journey
- Fuel used (approx.)
- 10.10 L
- Tailpipe CO₂ (approx.)
- 23.34 kg
Using 2.31 kg CO₂ per litre (petrol)
Real-world economy varies with driving style, load, and weather. Official factors for reporting change over time; this tool is for rough comparison only — not for regulatory or tax purposes.
Frequently asked questions
- What does this calculator measure?
- An approximate mass of carbon dioxide (CO₂) released from the exhaust when the fuel you burned for that journey is combusted. It does not include emissions from refining fuel, extracting oil, or building the car — only tailpipe CO₂ from the litres we estimate you used.
- Why different numbers for petrol and diesel?
- Each litre of diesel releases more CO₂ when burned than a litre of petrol, which is why we apply a higher kg CO₂ per litre factor for diesel. This is separate from local air-quality pollutants (like NOₓ or particulates), which this tool does not estimate.
- Where do the kg CO₂ per litre figures come from?
- We use commonly quoted UK combustion factors — about 2.31 kg CO₂ per litre for petrol and 2.68 kg per litre for diesel — in line with figures used in official-style reporting. Exact values in DEFRA and other tables are updated from time to time; use this as a rough guide, not a compliance figure.
- How do you estimate litres used?
- If you enter miles and UK MPG, we divide miles by MPG and multiply by litres per imperial gallon (4.54609 L). If you enter kilometres and L/100 km, we use distance ÷ 100 × L/100 km. Your real consumption may differ from the figure you type in.