Scope 1, 2 and 3 emissions explained

Almost every corporate carbon footprint is organised the same way: emissions are sorted into three "scopes" defined by the GHG Protocol Corporate Standard. The scopes separate what you emit yourself from what others emit to supply you or to use what you sell, so that the same tonne is not counted twice by the same company.

The three scopes in the standard's words

The Corporate Standard sets the minimum: "Companies shall separately account for and report on scopes 1 and 2 at a minimum." Scope 3 is optional under the Corporate Standard, but the separate Scope 3 Standard adds requirements for companies that report it, starting with: "Companies shall account for all scope 3 emissions and disclose and justify any exclusions."

Which greenhouse gases are covered

The Corporate Standard lists the six gases of the Kyoto Protocol: "carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulphur hexafluoride (SF6)". In 2013 the GHG Protocol added a seventh: it "now requires NF3 to be included in GHG inventories" (nitrogen trifluoride).

Each gas is converted to carbon dioxide equivalent (CO2e) by multiplying its mass by its global warming potential. For example, 1 kg of SF6 is 24,300 kg CO2e using the IPCC's sixth assessment report (AR6).

Scope 1: what you burn and release

Scope 1 covers emissions from sources you own or control. The Corporate Standard groups them by how they arise:

• Stationary combustion, such as boilers and generators ("combustion of fuels in stationary sources").
• Mobile combustion in company-owned or controlled vehicles.
• Process emissions from "physical or chemical processing", for example cement or chemicals.
• Fugitive emissions from "intentional or unintentional releases", most commonly refrigerant leaks from air conditioning and refrigeration.

Scope 2: the energy you buy

Scope 2 is the emissions released when the electricity, heat, steam or cooling you buy is generated. The power plant's emissions are someone else's Scope 1 but your Scope 2. Most companies report Scope 2 twice, using a location-based and a market-based method; see location-based vs market-based Scope 2.

Scope 3: the value chain

Scope 3 is everything else that happens because of your business, upstream (suppliers) and downstream (customers). The Scope 3 Standard splits it into 15 categories, from purchased goods and services (category 1) to investments (category 15). For many companies it is the largest part of the footprint. Category 3, the upstream emissions of the fuel and electricity you use, is usually the easiest place to start because it reuses your Scope 1 and 2 data.

A worked example

A small UK company with one office and two diesel vans, using DESNZ 2026 factors:

Scopes 1 and 2 total 67,945 kg CO2e (about 68 tonnes). The refrigerant line shows why fugitive emissions matter: 1.5 kg of gas equals almost 3 tonnes of CO2e. The category 3 figure comes from the worked example in the category 3 guide, and the diesel line is the kind of data a fuel card provides.

Where to start

1. Collect a year of energy bills and fuel records: that is Scope 1 and most of Scope 2.
2. Ask your maintenance contractor for refrigerant top-up records (kilograms added per system).
3. Add category 3 from the same data, then the Scope 3 categories where you spend the most.

The calculators linked below cover each step, and every result shows the factor, its source row and the file it came from.