Every Scope 1 and Scope 2 emissions figure comes down to the same underlying equation, repeated for each fuel type and each electricity source: activity data multiplied by an emission factor. That's genuinely the whole idea behind the GHG Protocol Corporate Standard's approach - the complexity people run into isn't the math itself, it's figuring out which activity data to collect and which emission factor actually applies to it. Here's both parts, worked through with real numbers.
Understanding Scope 1 (direct) vs. Scope 2 (indirect) boundaries
The GHG Protocol Corporate Standard - the methodology essentially every corporate emissions framework, including VSME, is built on - splits emissions into scopes based on who controls the source, not where the emissions physically end up.
- Scope 1Direct
- Direct emissions from sources your business owns or controls: fuel burned in company vehicles, generators, boilers, and other on-site equipment. If you're physically combusting the fuel, it's Scope 1.
- Scope 2Indirect
- Indirect emissions from purchased energy - almost always electricity, sometimes purchased heat or steam. You didn't burn anything yourself, but the power station that generated your electricity did, and Scope 2 attributes a share of that to you.
Scope 3 exists too - everything else in your value chain, both upstream (suppliers) and downstream (customers) - but it's far harder to calculate and isn't usually what a first supplier questionnaire or bank asks for. Scope 1 and Scope 2 are almost always the actual starting point, and often the whole request.
Step-by-step mathematical calculations for Scope 1 fuel consumption
The formula for any Scope 1 fuel source is the same shape every time:
Worked example: a company van burns 2,000 litres of diesel over the reporting year. Using the UK Government's 2026 DESNZ conversion factor for diesel - 2.58354 kgCO2e per litre, the same factor this site's own calculator uses - the calculation is:
Every fuel type - petrol, natural gas, LPG - works the same way, just with a different emission factor and a different unit (litres for liquid fuels, cubic metres for natural gas). The factor itself isn't something you calculate; it's a published, periodically-updated figure from a government or GHG Protocol source, and using a stale or wrong-country factor is one of the most common sources of a materially wrong Scope 1 number.
Converting Scope 2 electricity data using regional grid factors
Scope 2's formula has the same shape as Scope 1, just with electricity consumption and a grid emission factor in place of fuel quantity and a fuel factor:
Worked example: a business uses 50,000 kWh of electricity over the year. The UK's 2026 DESNZ/DEFRA grid factor is 0.131 kgCO2e per kWh:
The grid factor is where Scope 2 gets genuinely country-specific in a way Scope 1 mostly isn't - a country running mostly on nuclear or hydro can have a grid factor an order of magnitude lower than one running mostly on coal, so using the wrong country's factor produces a wrong answer that looks plausible. The GHG Protocol also distinguishes location-based reporting (the average factor for the grid you're physically connected to, which is what most SME questionnaires ask for) from market-based reporting (adjusted for any renewable energy contracts or certificates you've specifically purchased) - if a questionnaire doesn't specify which one it wants, location-based is the safer default.
Don't copy-paste utility bills for hours. Our free calculator applies the correct country-specific factors automatically and does the math in seconds - no signup required to see your result.
Where manual spreadsheets introduce errors
Every step above is simple arithmetic, but a spreadsheet doing this by hand fails in the same few places, repeatedly: an emission factor from the wrong country or the wrong year gets pasted in and never updated, a unit conversion gets missed (litres vs. gallons, kWh vs. MWh), or a fuel type gets matched to the wrong factor row entirely. None of these show up as an error - the spreadsheet still returns a number, it's just the wrong one, and it usually isn't caught until a reviewer or auditor asks where a specific figure came from. Manually managing these formulas in a spreadsheet also tends to introduce these kinds of errors precisely because nothing forces the factor to match the fuel, the country, or the year automatically. Many businesses end up offloading this to dedicated software for exactly that reason - see our breakdown of the best carbon accounting software for SMEs if you're weighing whether to keep doing this by hand.
Skip the manual math entirely.
Let our integrated AI document scanner extract your Scope 1 & 2 data from your actual utility bills automatically, for free - the correct factors are already applied for you.