Vessel CII Rating Lookup
The Carbon Intensity Indicator (CII) rates ships A to E based on how efficiently they use fuel relative to their cargo capacity and distance sailed. Enter an IMO number to see the vessel's CII rating, attained vs required intensity, and year-by-year trend calculated from EU MRV reported data.
CII is calculated from EU MRV reported data (CO2, distance, DWT). Coverage: vessels of 5,000 GT+ calling at EU/EEA ports, 2018–2024.
CII reduction factors by year
| Year | Reduction factor (Z) | Required CII vs reference |
|---|---|---|
| 2023 | 5% | 95% of reference line |
| 2024 | 7% | 93% of reference line |
| 2025 | 9% | 91% of reference line |
| 2026 | 11% | 89% of reference line |
Post-2026 reduction factors are under review at IMO. The regulation is expected to be strengthened as part of the revised MARPOL Annex VI framework.
How CII is calculated
CII uses the Annual Efficiency Ratio (AER) as the operational metric: AER = (annual CO2 in grams) / (DWT × distance in nautical miles). This gives a value in gCO2 per tonne-mile.
The required CII is derived from a type-specific reference line — the formula CIIref = a × DWT-c where a and c are constants from MEPC.354(78) — multiplied by (1 - Z/100) where Z is the annual reduction factor.
The attained AER is then compared against four boundary values (d1 through d4, also type-specific) applied to the required CII. These boundaries define the A-B-C-D-E rating bands. Larger ships generally have lower reference CII values (better expected efficiency per tonne-mile).
This tool uses EU MRV data as the source for CO2 and distance. MRV covers voyages to, from, and within the EU — it may differ from the vessel's global CII if its EU trade profile differs from its worldwide operations.
See also: EU ETS Cost Calculator and FuelEU Maritime Calculator.
Frequently Asked Questions
What is the CII rating?
The Carbon Intensity Indicator (CII) is an IMO measure of a ship's operational carbon efficiency. It expresses how many grams of CO2 the ship emits per tonne of cargo capacity per nautical mile sailed (gCO2/t·nm). Ships are rated A to E annually: A (superior) through C (moderate) are compliant, while D (minor inferior) and E (inferior) require a corrective action plan.
How is CII calculated?
CII is calculated as the Annual Efficiency Ratio (AER): total CO2 emissions (grams) divided by deadweight tonnage (DWT) multiplied by total distance sailed (nautical miles). The attained CII is compared against a type-specific reference line adjusted by annual reduction factors. The reference line formula is CII_ref = a × DWT^(-c), where a and c are constants that vary by ship type (MEPC.354(78)).
What happens if a ship gets a D or E CII rating?
A ship rated D for three consecutive years, or rated E in any single year, must submit a corrective action plan to its flag administration showing how it will achieve at least a C rating. Measures can include speed reduction, route optimisation, hull cleaning, or technical modifications. CII ratings are operational — they reflect how the ship is actually used, not just its design efficiency.
Does CII apply to all ships?
CII applies to all cargo and cruise ships of 5,000 GT and above engaged in international voyages, under IMO MARPOL Annex VI. It does not apply to ships below 5,000 GT, domestic-only vessels, or certain categories like fishing vessels and naval ships. The EU MRV regulation, which this tool uses as its data source, covers ships of 5,000 GT and above calling at EU/EEA ports.
How does CII differ from EEXI?
EEXI (Energy Efficiency Existing Ship Index) measures a ship's design efficiency — it is calculated once based on the vessel's technical specifications and does not change unless the ship is modified. CII measures operational efficiency — it changes every year based on how the ship is actually sailed. A ship might pass EEXI (good design) but fail CII (inefficient operation), or vice versa.
Where does the CII data come from?
This tool calculates CII from EU MRV (Monitoring, Reporting, Verification) data reported to THETIS-MRV. MRV reports include annual CO2 emissions and distance sailed for ships of 5,000 GT and above calling at EU/EEA ports. DWT is sourced from the vessel register. Coverage spans 2018–2024 reporting years.
Full emissions and compliance report for any vessel
VesselScore reports include CII ratings with year-by-year trend, EU ETS cost estimates, FuelEU compliance status, full MRV emissions data, plus PSC history, sanctions screening, and ownership chain.
Request accessCII reference lines and rating boundaries from IMO MEPC.354(78) and MEPC.364(79). Annual reduction factors from MEPC.338(76). CO2 and distance data from EU MRV (THETIS-MRV). DWT from vessel register. This tool provides estimates for informational purposes based on EU MRV-reported data and does not constitute official CII certification.