Maritime Knowledge Library

ACT-KA-000201 · IMO CII

What is CII?

CII means Carbon Intensity Indicator. It is an IMO operational efficiency rating that compares a ship's annual CO2 emissions with the transport work performed during the year. In simple terms, it answers: how much CO2 did the vessel emit for each unit of capacity carried over each nautical mile? The CII regime applies to ships of 5,000 gross tonnage and above that fall under the IMO fuel oil consumption Data Collection System. Each year, the vessel receives an A, B, C, D or E rating. A is the best rating and E is the worst rating. A vessel rated D for three consecutive years, or E for one year, needs a corrective action plan in SEEMP Part III.

ACT-KA-000202 · IMO CII

IMO rating bands for CII

IMO CII ratings are expressed as A, B, C, D or E. A means major superior performance, B means minor superior performance, C means moderate performance, D means minor inferior performance and E means inferior performance. The rating is based on how the ship's attained annual CII compares with the required annual CII and rating boundaries. The practical target is normally to maintain C or better. A D rating for three consecutive years or one E rating requires a corrective action plan showing how the vessel will return to C or better.

ACT-KA-000203 · Calculation Method

How CII ratings are calculated

CII calculation starts with annual fuel consumption. Fuel is converted into CO2 emissions, then divided by annual transport work. The result is the attained annual CII. That value is compared with the required annual CII and rating boundaries for the vessel type, size and reporting year. The calculation is simple in concept but sensitive to data quality. Incorrect fuel mapping, missing distance, wrong capacity basis, unsubmitted noon reports or duplicate reports can change the rating.

ACT-KA-000204 · Improvement Actions

How to improve CII

A vessel improves CII by reducing CO2 emissions for the same transport work, improving transport work for the same emissions, or both. Practical levers include speed management, weather routeing, trim optimization, hull and propeller cleaning, machinery performance monitoring, auxiliary load reduction, fuel choice, voyage planning and better port turnaround. CII improvement must be managed before year-end. Once the year closes, the rating is largely fixed except for permitted corrections or verified data adjustments.

ACT-KA-000205 · SEEMP

SEEMP Part III overview

SEEMP Part III is the ship operational carbon intensity plan. It supports IMO CII compliance by setting the vessel's CII target, monitoring method, implementation plan, responsible persons and corrective actions where required. SEEMP Part III should not be treated as a static document. It should be connected to monthly CII monitoring, fuel reporting, vessel performance review and management actions.

ACT-KA-000206 · IMO GHG Measures

CII vs EEXI

EEXI is a technical or design-efficiency requirement for existing ships. CII is an annual operational carbon intensity rating. EEXI asks whether the ship's technical efficiency meets the required standard. CII asks how efficiently the ship actually operated during the year. A ship can be EEXI compliant but still receive a poor CII rating if it is operated inefficiently, waits for long periods, consumes excessive fuel or has poor hull/engine performance.

ACT-KA-000207 · Emissions Reporting

IMO DCS vs EU MRV

IMO DCS and EU MRV both collect ship emissions-related data, but they are not the same scheme. IMO DCS is the global IMO fuel oil consumption data collection system and supports CII. EU MRV is the European monitoring, reporting and verification scheme for voyages involving EU/EEA ports and is connected to EU climate measures such as EU ETS. The same noon report and bunker data can support both schemes, but the reporting boundaries, gases, voyage definitions, verification process and submission platforms differ.

ACT-KA-000208 · Commercial Impact

Charter party implications of CII

CII affects chartering because operational decisions influence the annual rating. Speed orders, routeing, cargo utilization, ballast legs, waiting time and port delays can all change the vessel's CII outcome. This creates a need for clear charter party clauses, data sharing and decision records. The owner may be responsible for compliance, but charterers often influence the operating pattern. Therefore, CII should be discussed before fixtures and reviewed during voyages.

ACT-KA-000209 · EU ETS and Carbon Cost

Carbon taxes and EU ETS

Carbon pricing makes emissions a direct cost. Under the EU ETS maritime extension, shipping companies must surrender allowances for covered emissions, with phase-in percentages increasing over time. This creates financial exposure linked to fuel consumption, voyage scope, greenhouse gas type and allowance price. Carbon cost is not the same as CII rating, but both are driven by fuel consumption and operating efficiency. A vessel with high fuel consumption can face both weaker CII performance and higher carbon cost.