Does anyone measure my carbon with an instrument, or is it calculated from bills?

For most small companies it is calculated, not measured. The Greenhouse Gas (GHG) Protocol says measuring at the chimney is not common. For most small and medium companies, Scope 1 comes from fuel quantities bought and Scope 2 from metered electricity, each times a published factor.

Why you usually have no meter on your chimney

The Corporate Standard, the main GHG Protocol rulebook for company footprints, says direct measurement of emissions by monitoring concentration and flow rate is not common. More often emissions are calculated from a mass balance or stoichiometric basis specific to a facility or process. It adds that the most common approach is to apply documented emission factors, which it describes as calculated ratios relating emissions to a proxy measure of activity at a source.

Plain words: instead of catching the smoke, you count what went in, such as litres of diesel, and use a known ratio for what comes out.

What small companies use

• Scope 1: the purchased quantities of commercial fuels, such as natural gas and heating oil, with published emission factors.
• Scope 2: metered electricity consumption, with a supplier-specific, local grid or other published factor.
• The standard says that in many cases accurate emission data can be calculated from fuel use data, particularly when direct monitoring is either unavailable or prohibitively expensive.

Calculated is not the same as guessed

Your meter is real. Your electricity meter and your fuel invoice are measurements of what you used. The factor turns them into carbon. For Scope 3 the Corporate Standard (Chapter 4) says estimates are acceptable as long as there is transparency about the estimation approach and the data are adequate for the inventory's objectives.

What to keep

• The bill or invoice for each quantity.
• The factor, its unit and where it came from.
• A one-line note on any estimate and why.

Example: a generator's month

• Measured by instrument: not needed.
• Calculated: 320 litres of diesel on the invoices x 2.645 kilograms (kg) of carbon dioxide per litre = 846.4 kg.

Example quantity. 2.645 kg per litre is the diesel factor Senseible uses.

What Senseible does here

Senseible reads fuel invoices and electricity bills into records, so the quantities behind each figure are on file. It calculates from those quantities. Meters and sensors are custom, on request.

• What is an emission factor and how does a bill become carbon?
• Do I need smart meters for carbon reporting?
• Use tank dip readings for diesel burned?
• Free calculators

Sources: GHG Protocol Corporate Accounting and Reporting Standard, revised edition (Chapters 4 and 6, scopes and calculation methods), IPCC 2006 Guidelines, Volume 2 Energy, Chapter 1 (Tables 1.2 to 1.4)

Last reviewed 2026-11-07. Quotes are from Chapter 6 of the GHG Protocol Corporate Standard (revised edition), and the Scope 3 estimates sentence is from its Chapter 4. A scheme such as a carbon credit programme or a regulated plant can require real monitoring; check the scheme's own rules.