# Should our plant use the calculation or measurement approach for UK CBAM?

Canonical: https://senseible.earth/answers/uk-cbam-calculation-or-measurement

Usually calculation. HMRC's UK CBAM guidance defines it as fuel and material quantities times calculation factors; measurement uses greenhouse gas concentration and flue gas flow at each emission source. For CO2, measurement is allowed only with evidence that it is more accurate. For process N2O in nitric acid, measurement is mandatory.

## Calculation-based

- Fuel or material quantity times an emission factor, from standard values or lab analysis.
- Two forms: the standard method, which separates combustion and process emissions, and the mass balance, suited to complex sites such as an integrated steelworks.
- Works well where each fuel and material is bought, weighed and invoiced.

## Measurement-based

- A continuous emission monitoring system on the stack measures gas concentration and flue gas flow.
- Hard with many stacks, and impossible where emissions escape outside stacks.
- Its strength: it does not depend on knowing what was burned, for example with mixed wastes.
- Several sources that cannot be measured as one are measured separately and added.

## Using both

You can combine them, but only on different parts of the installation or to cross-check the same emissions. The monitoring plan must show there are no gaps and no double counting.

## A calculation-based line

- Furnace oil burned in the year: 1,200 t.
- Standard factor: 77.4 tCO2/TJ at 40.4 TJ per thousand tonnes, so 3.127 tCO2 per tonne.
- Emissions: 1,200 x 3.127 = 3,752 tCO2, before any oxidation factor.

Factors from HMRC's Annex VI standard values.

## What Senseible does here

Senseible reads fuel and material quantities from invoices, the activity data a calculation-based approach starts from. We build the figure from your records and check every figure in-house; for the UK it must then be verified by a verifier accredited for UK CBAM. Have your own verifier? Send it to them.

- [Standard fuel factors](https://senseible.earth/answers/uk-cbam-standard-fuel-emission-factors)
- [Monitoring plan contents](https://senseible.earth/answers/uk-cbam-monitoring-plan-contents)
- [CBAM Suite](https://senseible.earth/cbam-suite)

Sources: [HMRC, UK CBAM monitoring, reporting and verification technical guidance (October 2026)](https://assets.publishing.service.gov.uk/media/6ad219fe0f7b53973e02680f/CBAM_technical_guidance.pdf)

Last reviewed 2026-11-03.