UK Government conversion factors, explained

Every emissions figure in a Carbon Reduction Plan comes from the same simple sum: an amount of activity multiplied by a conversion factor. The conversion factors are the part you do not invent. They are published by the UK Government, updated every year, and using the current set is what makes your numbers defensible when a buyer asks how they were worked out. This guide explains what the factors are, where they come from and how to use them without tripping over the common mistakes.

What the conversion factors are

A conversion factor turns a unit of activity into a quantity of greenhouse gas. For example, it tells you how much carbon dioxide equivalent is released per kilowatt hour of grid electricity, per litre of diesel, or per mile driven in a particular type of vehicle. The result is expressed in carbon dioxide equivalent, written as CO2e, which rolls the different greenhouse gases into a single comparable number. Most raw factors are given in kilograms of CO2e, which you divide by a thousand to report your totals in tonnes.

Where they come from

The official set is the UK Government greenhouse gas conversion factors for company reporting, published on GOV.UK by the Department for Energy Security and Net Zero. A fresh set is published each year; the 2026 set was published on 11 June 2026. The electricity factor in particular changes as the grid gets cleaner, so the same amount of electricity can produce a different figure from one year to the next. This is why you should use the set for the activity year you are reporting rather than reusing an old one.

What they cover

The factors span most of what an SME needs for a Carbon Reduction Plan:

• Fuels such as natural gas, diesel, petrol and heating oil.
• Grid electricity, and heat or steam bought from a district network.
• Business travel by car, van, rail, bus and air, including flights by distance band.
• Freight and delivery transport.
• Water supply and treatment.
• Waste by disposal route, such as landfill, recycling and incineration.

The full set is organised so you can report Scope 1, Scope 2 and Scope 3 emissions separately, which helps when you are sorting your results into Scope 1, 2 and 3.

How to use them correctly

The arithmetic is easy. The care is all in matching units. A few rules keep you out of trouble:

• Use the factor set for the activity year you are reporting, not last year’s by habit.
• Match the units exactly. If a factor is per kilowatt hour, your activity has to be in kilowatt hours, not pounds spent.
• Pick the specific factor, not a generic one. A small diesel van and a large HGV have different factors for a reason.
• Keep a note of which factor you used for each line, so your figures can be checked later.

The most common mistakes

Two errors show up again and again. The first is reusing a previous year’s factors out of habit, which quietly makes your current-year figure wrong. The second is a unit mismatch, usually estimating from money spent rather than actual consumption, which can throw a total out by a wide margin. Both are easy to avoid once you know to look for them, and both are exactly the kind of slip that gets a plan queried after submission.

Frequently asked questions

Letting the calculation happen automatically

Because the factors change every year and the units have to line up, this is a natural thing to automate. Carbon Sorted holds the current government factors and applies the right one to each answer you give, so the figures are computed rather than typed in by hand, and never written by an AI. If you would rather not manage a spreadsheet of factors, you can start from the compliant template and let the engine do the sums. Our step-by-step writing guide shows where this fits into the wider process, and the free footprint calculator gives you a first estimate using indicative factors before you commit to the full workings.