How to calculate Scope 1 emissions: formulas, examples and documents
Scope 1 emissions are calculated by multiplying fuel consumption by the emission factor and the kg of refrigerant topped up by the GWP. Here are the formulas, three numerical examples and the documents to gather.
To calculate Scope 1 emissions, multiply the quantity of fuel consumed by sources your company owns or controls, such as boilers, generators and company vehicles, by the emission factor of that fuel. For refrigerant gases, multiply the kg topped up in the systems by their global warming potential (GWP). The total, expressed in tCO₂e, is your Scope 1.
What Scope 1 is and what it includes
The GHG Protocol defines Scope 1 as direct emissions: those released from sources your company owns or controls. If it burns in your plant or your van, or leaks from your air conditioner, it is Scope 1. There are four types of source.
- Stationary combustion. Gas boilers, generators, furnaces and process burners.
- Mobile combustion. Cars, vans, lorries, forklifts and work machinery that you own or lease and manage.
- Process emissions. Chemical reactions in production, for example in making cement, lime or glass.
- Fugitive emissions. Refrigerant gas leaks from air conditioners, cold rooms and heat pumps.
With the operational control approach, leased or long-term rental vehicles that you manage fall under Scope 1. Employees' own cars used for business trips with mileage reimbursement go under Scope 3 instead. For the full picture of the three scopes, you will find an explanation with examples in the article on Scope 1, 2 and 3.
The formula for calculating Scope 1
For combustion sources the formula is always the same: emissions (kgCO₂e) = quantity of fuel × emission factor. For fugitive emissions the calculation changes: emissions (kgCO₂e) = kg of refrigerant topped up × GWP of the gas. Divide by a thousand to get tCO₂e.
The trickiest step is the unit of measurement. The emission factor must be expressed in the same unit as the figure you find in your documents.
| Source | Starting data | Unit | Where to find it |
|---|---|---|---|
| Natural gas | Gas consumption | Smc | Gas bills |
| Diesel and petrol | Fuel purchased | Litres | Fuel invoices, fuel card statements |
| LPG | Fuel purchased | Litres or kg | Supplier invoices |
| Refrigerants | Gas topped up in the systems | kg | Maintenance contractor reports, F-gas declarations |
Three calculation examples
The factors below are indicative, rounded values, useful only to show the method. In your inventory, use up-to-date official factors and state the source and year.
| Source | Annual consumption | Indicative factor | Emissions |
|---|---|---|---|
| Office heating | 18,000 Smc of natural gas | about 2 kgCO₂e/Smc | 36 tCO₂e |
| Fleet of five vans | 22,000 litres of diesel | about 2.6 kgCO₂e/litre | 57.2 tCO₂e |
| Air conditioner top-up | 4 kg of R-410A | GWP about 2,000 | 8 tCO₂e |
Adding up the three sources, the example company's Scope 1 comes to 101.2 tCO₂e. The fleet accounts for more than half, and that is where it makes sense to start when planning reductions. Note the refrigerant too: a few kilos of gas weigh as much as thousands of litres of fuel.
Which emission factors to use
For fuels in Italy, the most widely used reference is the national standard parameters published every year by the Ministry of the Environment and Energy Security, consistent with the national emissions inventory. For refrigerants, the GWP comes from the IPCC assessment reports: always state which report you use, because the values change from one edition to the next.
Whichever source you choose, keep it the same for the whole year and note the version. If you change factor from one year to the next, recalculate the base year too, otherwise the reduction you show could depend on the factor rather than on consumption. Learn more in the guide to emission factors.
The calculation step by step
- Define the boundary. List the sites, plants and vehicles under your operational control for the reporting year.
- Map the sources. For each site, note boilers, generators, air conditioning and refrigeration systems; for the fleet, each vehicle with its fuel type and form of ownership.
- Gather twelve months of data. Gas bills, invoices and fuel cards, maintenance reports with the kg of gas topped up.
- Convert and multiply. Bring each consumption figure into the unit of the factor and apply the correct factor or GWP.
- Add up and document. Report the total by source and by site, with factors, sources and year, so that every number can be traced back to the document it comes from.
The most common mistakes
- Estimated readings treated as actual. Many gas bills show estimated consumption followed by adjustments: use the actual readings or reconstruct real consumption.
- Periods that do not match. A bill covering December and January must be split between the two years.
- Amounts spent instead of litres. Calculating emissions from fuel spending introduces errors linked to the price, which changes every week.
- Forgotten refrigerants. The data sits in the maintenance contractor's reports, far from the accounts office, and is often left out.
- Double counting the fleet. The same fuel cannot appear in both Scope 1 and Scope 3.
Scope 1 in the sustainability report
In a report following the voluntary VSME standard, Scope 1 emissions appear in disclosure B3 of the Basic module, together with location-based Scope 2 and total energy consumption. It is also the figure banks and clients check first: an inaccurate Scope 1 casts doubt on the whole inventory, while a well-documented one helps them calculate their own Scope 3 in turn.
Scope 1 is calculated by multiplying fuel consumption by the emission factor and the kg of refrigerant topped up by the GWP. Three things matter: start from quantities, not amounts spent, use official factors with source and year, and cover all four sources, refrigerants included.
Download the free Scope 1 guide
We have put the method together in a free PDF guide: the four emission sources, the formulas, three practical examples, the checklist of documents to gather and the mistakes to avoid. Download the guide to calculating Scope 1.
