Car Trip Carbon Emissions Calculator
Estimate the CO₂ emissions of a car trip from the distance, your fuel economy and the fuel type. Enter the route length and consumption to see the fuel burned and the CO₂ produced.
Estimate the CO₂ Emissions of Your Drive
Car Trip Carbon Emissions Formula
Where:
- \(CO_2\) — carbon dioxide emitted by the trip (kg)
- \(d\) — trip distance (km)
- \(E\) — fuel consumption (L/100 km)
- \(f\) — emissions factor of the fuel (kg CO₂ per litre)
The formula multiplies the distance by the consumption to get the litres of fuel burned, then multiplies by the fuel's emissions factor to convert litres into kilograms of CO₂. Distances in miles and consumption in MPG or km/L are converted to km and L/100 km before the calculation.
Car Trip Carbon Emissions – Calculation Example
Example: a 150 km trip in a petrol car that consumes 7.5 L/100 km on average, using the petrol emissions factor of 2.31 kg CO₂ per litre.
\[ \text{fuel} = 150 \times \frac{7.5}{100} = 11.25 \text{ L} \]
\[ CO_2 = 11.25 \times 2.31 = 25.99 \text{ kg} \]
Result: the car burns about 11.25 L (2.97 US gal) of petrol and emits approximately 25.99 kg (57.3 lb) of CO₂ over the trip.
How to use the calculator
- Enter the Trip distance and choose whether it is in kilometres or miles.
- Enter your Fuel economy and pick the matching unit: L/100 km, MPG (US), MPG (UK) or km/L.
- Select the Fuel type — petrol, diesel, LPG or E85. Each sets a standard emissions factor.
- If you know a different emissions factor for your fuel, tick Use a custom emissions factor and enter it in kg CO₂ per litre. Leave the box unticked to use the preset value.
- Read the results: estimated fuel burned in litres and US gallons, and trip CO₂ emissions in kilograms and pounds.
What the calculator tells you
Every litre of fuel burned in an engine releases carbon dioxide that was previously locked inside the fuel. Petrol emits about 2.31 kg of CO₂ per litre, diesel about 2.68 kg, LPG about 1.51 kg, and E85 about 1.97 kg. Because diesel packs more carbon per litre, a diesel car can burn less fuel than a petrol car and still emit a similar amount of CO₂ on the same trip.
The result is the direct "tailpipe" emission for one trip. It is the number most commonly used for personal carbon footprints, corporate travel reporting and voluntary offsetting schemes. For context, a typical passenger car emits roughly 120–180 g of CO₂ per kilometre, so a 150 km trip landing near 26 kg — about 173 g/km — is squarely in the normal range.
To interpret the result, it helps to compare it with everyday benchmarks. One economy-class flight kilometre emits a comparable amount per passenger, while rail travel typically produces a fraction of it. If you repeat the calculation for your regular commute and multiply by the number of trips per year, you get an annual driving footprint you can act on — by consolidating errands, carpooling, switching to a more efficient vehicle, or offsetting.
Assumptions and limitations
- Emissions factors are averages. The preset values (petrol 2.31, diesel 2.68, LPG 1.51, E85 1.97 kg CO₂/L) reflect typical published figures; actual fuel composition varies slightly by country and season.
- Fuel economy should match real conditions. Highway cruising, city traffic, cargo load, tyre pressure and driving style all change consumption. Use a figure measured on similar trips, not just the brochure value.
- Only tailpipe CO₂ is counted. Upstream emissions from producing and transporting the fuel (typically 15–25% extra) are not included.
- Electric vehicles are out of scope here, since they burn no fuel — their footprint depends on the electricity mix.
Planning a longer journey? Pair this calculator with the Road Trip Fuel Stops Calculator to see where to refuel, the Travel Budget Calculator to cost the whole trip, and the Flight Carbon Emissions Calculator to compare driving with flying the same route. If you drive for work, the Mileage Reimbursement Calculator handles the expense side.
Quick reference: emissions factors
| Fuel | kg CO₂ per litre |
|---|---|
| Petrol / gasoline | 2.31 |
| Diesel | 2.68 |
| LPG / autogas | 1.51 |
| E85 (85% ethanol) | 1.97 |
For fuels not listed — biodiesel blends, for example — enable the custom factor field and enter the value published by your national environmental agency.
Frequently Asked Questions
How do I convert MPG to L/100 km before calculating by hand?
Use these conversions: \( \text{L/100 km} = \frac{235.215}{\text{MPG (US)}} \) and \( \text{L/100 km} = \frac{282.481}{\text{MPG (UK)}} \). A common mistake is mixing up US and imperial gallons — a UK gallon is about 1.2 US gallons, so the same car shows a higher MPG figure in Britain. If your consumption is in km/L, divide 100 by it to get L/100 km.
Why does diesel emit more CO₂ per litre than petrol?
Diesel is denser and contains more carbon per litre than petrol, so burning one litre releases about 2.68 kg of CO₂ versus 2.31 kg for petrol. However, diesel engines typically burn 15–25% less fuel over the same distance, which is why diesel cars often show lower official g/km figures. The total trip emission depends on both the factor and your real-world consumption.
Does a round trip count as double the emissions?
Yes. Enter the total distance you will actually drive, so for a round trip double the one-way distance. If your return route is longer or involves different driving conditions (for example, a fully loaded car or a mountain pass), estimate the legs separately with a realistic consumption figure for each and add the results.
What is a good CO₂ figure for a car trip?
A useful benchmark is grams per kilometre: divide your trip CO₂ in kg by the distance in km and multiply by 1000. Modern petrol cars emit roughly 120–180 g/km, hybrids 90–120 g/km, and large SUVs can exceed 200 g/km. Below 120 g/km is efficient for a conventional car. Note that real-world figures are usually 10–20% higher than official laboratory values.
Can I divide the result by the number of passengers?
Yes, if you want a per-person footprint for comparison with flights or trains. A trip emitting 26 kg of CO₂ with two people on board works out to 13 kg per person. This is the standard method used in carbon accounting and offsetting schemes, because sharing a vehicle spreads the same total emission over more travellers.
How do I turn one trip result into my annual driving footprint?
Calculate a typical trip, then multiply by how often you make it. For a daily 40 km commute at 6 L/100 km: \( 40 \times \frac{6}{100} \times 2.31 \approx 5.5 \) kg per day, or about 1.4 tonnes per year for roughly 250 working days. Summing all your regular routes gives a full picture you can use to plan reductions or offsets.
How do I estimate emissions for an electric car?
This calculator cannot do it directly, because EVs burn no fuel. Instead, take the consumption in kWh per 100 km, multiply by the distance, then multiply by your electricity grid's emission factor in kg CO₂ per kWh (your energy provider usually publishes it). In coal-heavy grids an EV can approach petrol emissions; on clean electricity it produces a small fraction of them.