Carbon Intensity Indicator (CII)
An IMO operational measure of how much CO₂ a ship emits per unit of transport work, graded A to E each year.
- Category
- Regulation and Compliance
- Abbreviation
- CII
- Rating scale
- A to E, yearly
- Applies to
- ships of 5,000 GT and above
- Dictionary entry
- CII
- Last reviewed
How it works
The Carbon Intensity Indicator (CII) is the IMO’s operational efficiency metric: it measures grams of CO₂ emitted per deadweight-tonne-mile (or capacity-mile) over a calendar year and assigns each applicable ship an annual rating from A (best) to E (worst).
Required reduction factors tighten the thresholds each year, so a ship rated A or B today can slip without efficiency action. A D rating for three consecutive years, or an E in any year, requires a corrective action plan. CII applies to ships above a gross-tonnage threshold and is set under IMO MEPC resolutions.
Where it shows up on The Maritime
Also known as: CII, carbon intensity indicator, CII rating.
The short dictionary definition is at Dictionary entry: CII. This page is the explainer.
Related terms
Energy Efficiency Existing Ship Index (EEXI)
A one-time IMO design-efficiency standard that existing ships must meet, the in-service counterpart of the EEDI for new ships.
International Maritime Organization (IMO)
The United Nations agency that sets global rules for ship safety, security and pollution prevention.
Slow Steaming
The practice of sailing deliberately below design speed to cut fuel consumption, emissions and effective fleet supply.
Very Low Sulphur Fuel Oil (VLSFO)
Marine fuel blended to the global sulphur cap: the compliant fuel for most waters since the IMO sulphur rules took effect.
More regulation and compliance terms
A plain-English reference definition: our own explanation of a standard shipping concept, not a licensed source or legal advice. See the full glossary or the broader maritime dictionary.
Last reviewed: .