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Car CO₂ emissions calculator

Estimate the CO₂ your car emits over a distance from its emission factor.

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The Car CO₂ emissions calculator turns Distance (km), Emissions (g CO₂/km) into Total CO₂ (kg), Total CO₂ (t), instantly and for free. For instance, with Distance (km) = 15,000 and Emissions (g CO₂/km) = 120 it returns Total CO₂ (kg) = 1,800 and Total CO₂ (t) = 1.8.

How to use it

  1. Enter your values: Distance (km), Emissions (g CO₂/km).
  2. Read the result instantly: Total CO₂ (kg), Total CO₂ (t).

Frequently asked questions

How does the Car CO₂ emissions calculator work?

It takes Distance (km) and Emissions (g CO₂/km) and derives Total CO₂ (kg) and Total CO₂ (t) from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

2 values: Distance (km) and Emissions (g CO₂/km). Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Distance (km) = 15,000 and Emissions (g CO₂/km) = 120, the calculator returns Total CO₂ (kg) = 1,800 and Total CO₂ (t) = 1.8. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

How much does the result change with different inputs?

It moves a lot. Using Distance (km) = 16,500 and Emissions (g CO₂/km) = 240 instead, Total CO₂ (kg) goes from 1,800 to 3,960 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Distance (km) = 13,500 and Emissions (g CO₂/km) = 60, Total CO₂ (kg) comes out at 810. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Deciding between two cars, or between keeping one and replacing it: fuel or charging, insurance, depreciation and what a kilometre really costs.

What is the most common mistake?

Comparing on fuel alone. Depreciation is usually the largest line in the first years and dwarfs the difference in consumption between two comparable cars.

What is the difference between the Car CO₂ emissions calculator and the Car lease calculator?

This one returns Total CO₂ (kg) and Total CO₂ (t); the Car lease calculator returns Monthly payment and Residual value. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Car affordability calculator is the closest one after this: Find a sensible monthly and yearly car budget from your income.

What else is worth having open alongside it?

Car depreciation calculator and Fuel cost calculator — they come up in the same task often enough to be worth a second tab.

Further reading

All guides →
ExplainerWhat a Car's CO2 Figure Actually MeasuresA car's CO2 number and its fuel consumption number are the same measurement in different units, tied together by chemistry that you can do on paper. Here is the derivation, and then the three things the figure quietly leaves out.ExplainerCompression Ratio, and What Actually Limits ItEfficiency rises with compression ratio, so why do petrol engines stop around 12:1? Because compressing a charge heats it — r to the power of gamma minus one — and above a certain temperature the unburnt end gas lights itself.ExplainerThe Fuel Saving That Is Not LinearGoing from 10 to 20 mpg saves six times more fuel than going from 30 to 40, over the same distance. The reason is that fuel used is the reciprocal of fuel economy — and it changes which vehicle you should replace first.ExplainerFiscal Horsepower Is Not HorsepowerSeveral European countries tax cars on an administrative power figure that nobody has ever measured — it is the output of a formula, the formula differs by country, and it has been rewritten more than once. Here is what each market actually taxes, worked through on one car.ExplainerA Company Car Is Pay: What the Benefit in Kind Costs You in France, Germany and ItalyNobody negotiates a company car as a pay cut, but that is what the tax treatment makes it. Three countries value the same car by three completely different methods, one of them changed in 2025 in a way that nearly doubled the figure, and in all three an electric car is taxed at a fraction of the same vehicle with an engine.ComparisonCar Lease vs Buy: Which Costs Less Over Time?Leasing means lower monthly payments and endless flexibility; buying costs more up front but leaves you owning an asset. Here is how the total cost really compares.