What is the emission factor for diesel?

2.58354 kg CO2e a litre for UK forecourt diesel in the government's 2026 set, tank-to-wheel, or 3.19 well-to-wheel. The US EPA's 2025 hub gives 10.21 kg CO2 a gallon.

Where do emission factors come from?

National governments and standard setters publish them: the UK's Department for Energy Security and Net Zero every June, and the US EPA in its emission factors hub. Frameworks for freight, such as the GLEC Framework, publish default factors too.

Is fuel-based or distance-based calculation better?

Fuel-based, where the data exists. It uses what was actually burned; the distance-based method relies on average fuel use, loading and mass, so its accuracy is generally lower.

Term

Emission factor

An emission factor is a number that converts an activity — litres of fuel burned, tonne-kilometres moved — into greenhouse gas emissions: emissions equal activity data times the factor. For diesel, the UK government's 2026 factors give 2.58 kg CO2e a litre, and the US EPA's 2025 hub gives 10.21 kg CO2 a gallon.

Also called emissions factor, GHG conversion factors, DEFRA conversion factors, EPA emission factors hub, diesel emission factorUpdated 13 October 2026

Two ways to use them

Method	Activity data	Accuracy
Fuel-based	Litres of fuel or kWh actually used	Higher — the UK guidance asks for it where possible
Distance-based	Tonnes × kilometres moved	Lower — it assumes average fuel use, loading and mass

The EPA defines an emissions factor as a representative value relating the quantity of a pollutant released to the activity that released it; the UK guidance reduces it to one line — GHG emissions equal activity data times the conversion factor. The UK publishes a new set every June, for activity falling entirely or mostly in that year; its 2026 set came out on 11 June 2026. The EPA's hub is in its 2025 edition. Forecourt diesel in the UK should use the 'average biofuel blend' factor, not the 100% mineral one.

Worked example: 1,000 litres of diesel

UK 2026: 1,000 L × 2.58354 = 2,584 kg CO2e tank-to-wheel · + 1,000 × 0.61101 = 611 kg well-to-tank → 3,195 kg well-to-wheel · US: 1,000 L = 264.17 gal × 10.21 = 2,697 kg CO2 (combustion CO2 only)

The two answers differ because they measure different things: the UK figure is CO2e for blended diesel, the US one CO2 alone from diesel fuel, before methane and nitrous oxide are added.

The mistake people make

Using a distance-based factor when fuel data exists, or last year's set for this year's activity. The GHG Protocol notes distance-based accuracy is generally lower than fuel-based because it assumes average fuel consumption, loads and vehicle loading; and each UK set is meant for activity in its own year. Ask carriers for litres per lane before reaching for a tonne-km factor.

FAQ

Emission factor: common questions

What is the emission factor for diesel?: 2.58354 kg CO2e a litre for UK forecourt diesel in the government's 2026 set, tank-to-wheel, or 3.19 well-to-wheel. The US EPA's 2025 hub gives 10.21 kg CO2 a gallon.
Where do emission factors come from?: National governments and standard setters publish them: the UK's Department for Energy Security and Net Zero every June, and the US EPA in its emission factors hub. Frameworks for freight, such as the GLEC Framework, publish default factors too.
Is fuel-based or distance-based calculation better?: Fuel-based, where the data exists. It uses what was actually burned; the distance-based method relies on average fuel use, loading and mass, so its accuracy is generally lower.

Emission factor

Two ways to use them

Worked example: 1,000 litres of diesel

The mistake people make

Emission factor: common questions

Sources

Related terms