# Why does a litre of diesel make about three times its own weight in carbon dioxide (CO2)?

Canonical: https://senseible.earth/answers/why-diesel-makes-three-times-its-weight-in-co2

Because the fuel's carbon joins oxygen from the air as it burns, and carbon dioxide is heavier than the carbon alone. A litre of diesel weighs about 0.83 kilograms but gives 2.645 kilograms of CO2, roughly 3.2 times its weight.

## The candle comparison

Watch a candle burn. It gets shorter, and the wax seems to vanish. It has not vanished. It has left as gas in the air. Diesel does the same thing, and on the way out its carbon picks up oxygen from the air. The tank loses the fuel's weight, and the exhaust carries away more than that weight, because the oxygen was not in the tank.

## The three steps in the Intergovernmental Panel on Climate Change (IPCC) tables

1. Carbon in the fuel: the IPCC table gives gas or diesel oil 20.2 kilograms (kg) of carbon for every gigajoule (GJ) of heat. A gigajoule is a unit of heat energy.
2. Heat in a tonne: the same IPCC guide gives 43.0 GJ per tonne of diesel. So a tonne holds 20.2 x 43.0 = 868.6 kg of carbon.
3. Add the oxygen: one carbon of weight 12 makes one carbon dioxide of weight 44, so multiply by 44/12. 868.6 x 44/12 = about 3,185 kg of CO2 from one tonne of diesel.

## A small rounding gap, explained

The IPCC prints the finished factor as 74,100 kg per terajoule, which is 74.1 kg per GJ. 74.1 x 43.0 = 3,186.3 kg per tonne. The gap of about 1.4 kg to 3,185 comes from the IPCC rounding 20.2 x 44/12 = 74.07 up to 74.1. Nothing is wrong with either.

The IPCC also states that 99 to 100 percent of the carbon is oxidised and that its default factors assume 100 percent.

## From a tonne to a litre

Bills come in litres. Senseible uses 0.83 kg per litre for diesel, so 3.1863 x 0.83 = 2.645 kg of CO2 per litre. The same method gives liquefied petroleum gas (LPG) 63.1 x 47.3 = 2.9846 kg per kilogram, which Senseible rounds to 2.98.

## Example: a generator that burns 200 litres

- Fuel weight: 200 x 0.83 = 166 kg
- CO2 produced: 200 x 2.645 = 529 kg
- Ratio: 529 / 166 = about 3.19 times the weight of the fuel

Example quantity. The 0.83 kg per litre density is the figure Senseible uses for diesel.

## What Senseible does here

Senseible reads fuel invoices and electricity bills into records, so the quantities behind each figure are on file. It applies the diesel factor per litre. Readings from a generator or exhaust are custom, on request.

- [What a tonne of CO2 looks like](https://senseible.earth/answers/what-does-a-tonne-of-co2-look-like)
- [Convert diesel, LDO or furnace oil from kg to litres](https://senseible.earth/answers/diesel-kg-to-litres-conversion)
- [How much CO2 does a 19 kg LPG cylinder make?](https://senseible.earth/answers/lpg-19-kg-cylinder-co2)
- [Free calculators](https://senseible.earth/calculators)

Sources: [IPCC 2006 Guidelines, Volume 2 Energy, Chapter 1 (Tables 1.2 to 1.4)](https://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2.html)

Last reviewed 2026-11-07. Carbon content, heat value and the 44/12 step are from IPCC 2006 Guidelines Volume 2 Chapter 1 Tables 1.2 to 1.4. The litre figure uses the density Senseible applies (0.83 kg per litre); re-check if Senseible changes its diesel factor. Older pages may show 2.68 kg per litre, from before the density was fixed at 0.83.