CBAM calculation methods

Scope, reporting period and factor library

The installation is modelled as production processes, inputs (fuels, materials, purchased precursors, electricity and heat) and flows. New diagrams are calculated with the definitive-period methods (Implementing Regulation (EU) 2025/2547, Annexes II–III); older diagrams continue to be calculated with the transitional-period rules (Implementing Regulation (EU) 2023/1773, Annex III). The result of a finalised diagram does not change.

For every period that touches 2026, the reporting period is the calendar year. The factor library is generated by script from the official tables of Implementing Regulation (EU) 2025/2547 and no value is typed by hand: Annex II section G, Tables 1–6 (fuels, biomass, carbonates, metal oxides, iron and steel process materials, global warming potentials), Annex II section B.7, Tables 2–3 (PFC technology factors) and Annex III section C, Tables 1–2 (reference efficiencies).

Legal basis (EU) 2025/2547 Art. 7(1), Annex II G, Annex II B.7, Annex III C; (EU) 2023/1773 Annex III

Official source(EU) 2025/2547(EU) 2023/1773

Fuels: standard methodology

The combustion emissions of each fuel entering a process are the product of the fuel quantity, the net calorific value, the emission factor and the oxidation factor. The conservative oxidation factor of 1 may always be used. The biomass fraction may only be greater than zero if the conditions of Annex II section B.3.3 are met; if it is unknown, 0 is used.

Library values come from Annex II section G, Table 1 (fuels) and Table 2 (biomass). Annex II section B.5.2 allows type I (IPCC) and type II values (national inventory, supplier, laboratory); where a type II value exists, type I may not be used. An own value requires a source and a justification.

• Em = AD × EF × OF
• AD = FQ × NCV
• EF = EF_pre × (1 − BF)

Symbols Em: emissions (t CO2) · AD: activity data (TJ) · FQ: fuel quantity (t) · NCV: net calorific value (TJ/t) · EF: emission factor (t CO2/TJ) · OF: oxidation factor · BF: biomass fraction

Legal basis (EU) 2025/2547 Annex II B.3.1.1, Equations 5, 6 and 10; Annex II B.3.3, B.5.2; Annex II G, Tables 1–2

Official source(EU) 2025/2547Commission Guidance No. 3

Fuels and materials: mass balance

The mass balance tracks the carbon entering and leaving a process: the quantity of each flow is multiplied by its carbon content and the factor f. Outgoing flows (slag, dust, by-products, carbon remaining in the product) have a negative quantity. There is no oxidation factor in the mass balance.

If no carbon content is entered, it is derived from the emission factor: for fuels using the net calorific value (Equation 13), for materials directly (Equation 14). The biomass fraction is deducted from the carbon content (Equation 15).

• Em = f × AD × CC, f = 3.664
• CC = CC_pre × (1 − BF)
• CC = EF × NCV / f (fuel) · CC = EF / f (material)

Symbols AD: quantity of the flow (t; negative for outgoing flows) · CC: carbon content (t C/t) · BF: biomass fraction

Legal basis (EU) 2025/2547 Annex II B.3.2, Equations 12–15

Official source(EU) 2025/2547

Process emissions

The process emissions of raw materials and intermediate products are the product of the activity data, the emission factor and the factor CF; the conservative value of CF is 1.

For carbonates, method A (Annex II section G, Table 3, mass of carbonate input) or method B (Table 4, mass of metal oxide in the output) is used; for non-carbonate process emissions, method A.

• Em = AD × EF × CF

Legal basis (EU) 2025/2547 Annex II B.3.1.2, Equation 11; Annex II G, Tables 3–4

Official source(EU) 2025/2547

PFC emissions in aluminium

In primary aluminium electrolysis, CF4 and C2F6 emissions are calculated with the slope or the overvoltage method, converted to total emissions with the collection efficiency and expressed as CO2 equivalent with the global warming potentials (Annex II section G, Table 6: CF4 6,630, C2F6 11,100).

The technology factors are in Annex II section B.7, Tables 2–3 (minimum requirement); an installation-specific factor is the recommended improvement. The collection efficiency is mandatory.

• PFC_total = PFC_stack / collection efficiency
• CF4 = AEM × SEF_CF4 / 1,000 × Pr_Al, AEM = frequency × duration
• CF4 = OVC × AEO / CE × Pr_Al × 0.001
• C2F6 = CF4 × F_C2F6
• CO2e = CF4 × GWP_CF4 + C2F6 × GWP_C2F6

Legal basis (EU) 2025/2547 Annex II B.7, Equations 20–26; Annex II B.7, Tables 2–3; Annex II G, Table 6

Official source(EU) 2025/2547

Electricity

The indirect emissions of purchased electricity are the electricity consumed multiplied by the emission factor. For grid electricity the country average (the default in Implementing Regulation (EU) 2025/2621) is used; these data come from the IEA and are published under a non-commercial licence, so they are not embedded in Carbonity and the user enters the value with its source. For a direct technical link or a power purchase agreement, an actual factor may only be used with evidence that the conditions of point 6 of Annex IV to Regulation (EU) 2023/956 are met.

If the installation receives electricity from several sources, the indirect emissions of each process are calculated with the factor weighted by each source's share of consumption (Art. 9(1)); with evidence, each process uses its own source (Art. 9(2)). For electricity produced in the installation, the factor is the emissions of the fuels and of flue gas cleaning divided by the net electricity produced; this equation has no oxidation factor, and waste gas is capped at the standard factor of natural gas (56.1).

• Em_el = E_el × EF_el
• EF_el = (Σ AD × NCV × EF + Em_FGC) / El_prod

Symbols E_el: electricity consumed (MWh) · EF_el: emission factor (t CO2/MWh) · Em_FGC: flue gas cleaning emissions · El_prod: net electricity produced (MWh)

Legal basis (EU) 2025/2547 Art. 8(2), Art. 9; Annex II D.1, Equation 35; Annex II D.4.1, Equation 38; Annex II D.4.3; (EU) 2023/956 Annex IV point 6

Official source(EU) 2025/2547(EU) 2025/2621(EU) 2023/956

Measurable heat

The measurable heat produced in a central heat unit is the fuel energy input multiplied by the efficiency; the efficiency is measured or the reference value 0.70 is used. The emissions assigned to a heat-consuming process are proportional to the heat consumed, via the emission factor of the fuel mix. Heat not distributed to processes counts as a loss and is added to the consuming processes in proportion to their consumption; all of the heat is assigned.

For heat purchased from outside the installation, either the data of the installation producing the heat (factor and source required) or the standard factor of the most common fuel in the country's industrial sector with a boiler efficiency of 90% is used.

• Q = η × E_In, E_In = Σ AD × NCV
• EF_mix = (Σ AD × NCV × EF + Em_FGC) / Σ AD × NCV
• Em_heat = EF_mix × Q_consumed / η

Symbols Q: heat produced (TJ) · η: efficiency · E_In: fuel energy input (TJ) · EF_mix: emission factor of the fuel mix (t CO2/TJ)

Legal basis (EU) 2025/2547 Annex II C.1.2, Equations 32–33; Annex III A.2.2, Equations 44–45

Official source(EU) 2025/2547

Cogeneration (CHP)

The emissions of a cogeneration unit are split between heat and electricity in proportion to the ratio of the actual efficiencies to the reference efficiencies. If the efficiency cannot be measured, design values are used, and failing those the standard values (heat 0.55, electricity 0.25). The reference efficiencies are in Annex III section C, Tables 1–2 (fuel category, year of construction, heat medium).

The heat share is recorded as direct emissions of the process consuming the heat, the electricity share as indirect emissions of the process consuming the electricity; F_el is calculated in the same way.

• Em_CHP = Σ AD × NCV × EF + Em_FGC
• η_heat = Q_net / E_In, η_el = E_el / E_In
• F_heat = (η_heat / η_ref,heat) / (η_heat / η_ref,heat + η_el / η_ref,el)
• EF_CHP,heat = Em_CHP × F_heat / Q_net
• EF_CHP,el = Em_CHP × F_el / E_el

Legal basis (EU) 2025/2547 Annex III A.2.2, Equations 46–52; Annex III C, Tables 1–2

Official source(EU) 2025/2547

Waste gas

For waste gas produced by one process and used by another, the consuming process receives the quantity calculated with the standard emission factor of natural gas (EF_NG = 56.1, Annex II section G, Table 1); the producing process deducts the same quantity with the correction factor 0.667. In the producing process, the carbon of the waste gas stays in the mass balance.

• WG_corr,imp = V × NCV × EF_NG
• WG_corr,exp = V × NCV × EF_NG × Corr_η, Corr_η = 0.667

Symbols V × NCV: energy content of the waste gas (TJ) · EF_NG: standard emission factor of natural gas (t CO2/TJ)

Legal basis (EU) 2025/2547 Annex III A.3, Equations 53–54; Annex II G, Table 1

Official source(EU) 2025/2547

Attributing emissions to processes and goods

The attributed direct emissions of a process are its direct emissions plus imported measurable heat and waste gas, minus exported heat and waste gas and the emissions of electricity production; a negative result is set to zero.

The activity level is the saleable net mass: rejects, by-products, waste and scrap are not counted and enter another process with zero embedded emissions. A production process covers a single functional unit; where goods with the same CN code come from several processes, the common value is the average weighted by activity level.

• AttrEm_Dir = DirEm* + Em_H,imp − Em_H,exp + WG_corr,imp − WG_corr,exp − Em_el,prod
• AttrEm_Dir < 0 ⇒ AttrEm_Dir = 0

Symbols DirEm*: direct emissions of the process · Em_H,imp / Em_H,exp: emissions of imported / exported measurable heat · Em_el,prod: emissions of electricity production

Legal basis (EU) 2025/2547 Art. 4(2), 4(6); Annex II F; Annex III A.3, Equation 55

Official source(EU) 2025/2547

Specific embedded emissions (SEE) and precursors

The specific embedded emissions of a good are the emissions attributed to it plus the embedded emissions of the input precursors, divided by the activity level. Direct and indirect emissions are calculated separately; a precursor produced in the same installation is calculated with the same method along the chain.

Indirect emissions are only counted for goods not listed in Annex II to Regulation (EU) 2023/956 (cement, calcined clay, fertilisers, agglomerated iron ore); for iron and steel, aluminium, hydrogen and electricity, embedded emissions are direct emissions only.

• SEE_g = (AttrEm_g + EE_InpMat) / AL_g
• EE_InpMat = Σ M_i × SEE_i

Symbols AL_g: activity level of the good (t) · M_i: mass of the precursor used (t) · SEE_i: specific embedded emissions of the precursor (t CO2e/t)

Legal basis (EU) 2025/2547 Art. 3(2); Annex III B, Equations 59–60; (EU) 2023/956 Art. 7(1), Annex II, Annex IV point 3

Official source(EU) 2025/2547(EU) 2023/956

Default values and mark-up

If there are no actual data for a purchased precursor, the value for the country and CN code in Annex I to Implementing Regulation (EU) 2025/2621 (as amended by Implementing Regulation (EU) 2026/1740) is used; the total value is binding, the direct and indirect values are for information only. In the definitive period there is no upper limit on the use of default values for precursors; the share of default values is shown weighted by emissions.

According to Commission Q&A 4.25, the operator uses the default value for a precursor increased by the relevant mark-up: for cement, iron and steel, aluminium and hydrogen 10% for 2026, 20% for 2027 and 30% from 2028; 1% for fertilisers. The mark-up is not added to the supplier's actual data or to 2025 and earlier.

• SEE_precursor = SEE_default × (1 + mark-up)

Legal basis (EU) 2025/2621 Annex I; (EU) 2026/1740 Annex I introductory paragraph and recital 10; (EU) 2025/2547 Art. 15; Commission Q&A 4.25

Official source(EU) 2025/2621(EU) 2026/1740(EU) 2025/2547Commission Q&A

Embedded emissions from the bill of materials

For each product produced in the period, the usage quantity of every CBAM-covered precursor in the bill of materials (gross quantity, including losses) is multiplied by the precursor's specific embedded emissions and summed; the product's period SEE is this sum divided by the mass produced. A semi-finished product can be a line in another product's bill of materials: its period SEE from the same calculation is used as a precursor SEE (cycles are not allowed, at most 10 levels).

One scope is used per precursor: direct emissions for goods in Annex II to Regulation (EU) 2023/956 (iron and steel, aluminium, hydrogen, electricity), total emissions for the others. The product result is not split into direct and indirect emissions; there is no rule in force on this for downstream products.

• EE_product = Σ M_i × SEE_i
• SEE_product = EE_product / mass produced

Symbols M_i: mass of the precursor used in the period according to the bill of materials (t) · SEE_i: specific embedded emissions of the precursor (t CO2e/t)

Legal basis (EU) 2023/956 Annex IV points 1 and 3; (EU) 2025/2547 Art. 3(2); Annex III B, Equations 59–60

Official source(EU) 2023/956(EU) 2025/2547

Several source installations

If a precursor with the same CN code comes from several source installations, its SEE is the average weighted by the period mass received from each installation.

• SEE_CN = Σ m_k × SEE_k / Σ m_k

Symbols m_k: mass of the precursor from installation k (t) · SEE_k: specific embedded emissions of that installation (t CO2e/t)

Legal basis (EU) 2025/2547 Art. 14(1)–(2)

Official source(EU) 2025/2547

Actual value or default value

In periods from 2026 onwards, the actual value of a precursor is only used if it is verified: a positive verification report or a positive verifier opinion on the platform; acceptance in the supply chain alone is not enough. Data years before 2026 are not used.

If the actual value cannot be used, the precursor falls back to the default value in Annex I to Implementing Regulation (EU) 2025/2621 (as amended by (EU) 2026/1740) for the country of the source installation and the CN code, and the mark-up for the year is added; the calculation detail shows the table value and the mark-up separately.

• SEE_i = verified actual value (for the year of the period)
• otherwise: SEE_i = default value × (1 + mark-up)

Legal basis (EU) 2023/956 Art. 8(1), Annex VI point 1(b); (EU) 2025/2621 Annex I; (EU) 2026/1740 Annex I

Official source(EU) 2023/956(EU) 2025/2621(EU) 2026/1740

From embedded emissions to the number of certificates

In the annual declaration, the embedded emissions of each item are determined: the actual value is only used if it relates to the item's reporting year and is verified; otherwise the official total default value plus the mark-up for the year. For Annex II goods, only direct emissions are counted.

The free allocation adjustment is calculated with the CBAM factor, the CSCF and the SEFA of the good. A carbon price effectively paid in the country of origin is only deducted for actual data. Certificates are surrendered by 30 September of the year following the declaration year; for 2026 the certificate price is a quarterly average. If the annual threshold of 50 tonnes (excluding electricity and hydrogen) is not exceeded, there is no obligation.

• Embedded emissions = M_g × SEE_g
• FAA = CBAM_y × CSCF_y × SEFA_g × M_g
• SEFA_g = BM*_g + Σ m_i × SEFA_i, m_i = M_i / AL_g
• Certificates = max(0, embedded emissions − FAA − deduction for carbon price paid)

Symbols M_g: mass of the imported good (t) · FAA: free allocation adjustment · CBAM_y: CBAM factor for the year · SEFA: specific embedded free allocation · BM*_g: CBAM benchmark of the good

Legal basis (EU) 2023/956 Art. 2a, 6, 7(1), 8(1), 9(1), 21(1a), 22(1); (EU) 2025/2620 Equations 1 and 4–6; (EU) 2025/2548; (EU) 2026/1740 Annex I

Official source(EU) 2023/956(EU) 2025/2620(EU) 2025/2548(EU) 2026/1740Commission Guidance No. 4