The Carbon Intensity Indicator (CII) is a rating system for ships that the International Maritime Organization (IMO) developed. This will be a mandatory measure under MARPOL Annex VI, which comes into force in 2023.
The measure will impact all cargo, RoPax and cruise vessels above 5,000 gross tonnage (GT) and trading internationally.
The CII determines the annual reduction factor needed to continuously improve the ship's operational carbon intensity within a specific rating level. The actual annual operational CII achieved will need to be documented and verified against the required annual operational CII.
This will then enable the operational carbon intensity rating to be determined on a scale of A, B, C, D or E, indicating a major superior, minor superior, moderate, minor inferior, or inferior performance level. The performance level will need to be recorded in the ship's Ship Energy Efficiency Management Plan (SEEMP). A ship rated D or E for three consecutive years will need to submit a corrective action plan to show how the required index rating (C or above) will be obtained.
This short-term measure aims to achieve the carbon intensity reduction aims of the IMO's initial GHG emissions strategy.

Calculate your CII rating
Use our calculator to review your vessel’s Carbon Intensity Indicator rating (A to E).
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CII resources
CII resources
- Resolution MEPC.346(78) – 2022 Guidelines for the Development of a SEEMP
- Resolution MEPC.347(78) – Guidelines for the Verification and Company Audits by the Administration of SEEMP Part III
- Resolution MEPC.348(78) – 2022 Guidelines for Administration Verification of Ship Fuel Oil Consumption Data and Operational Carbon Intensity
- Resolution MEPC.352(78) – 2022 Guidelines on Operational Carbon Intensity Indicators and the Calculation Methods (CII Guidelines, G1)
- Resolution MEPC.353(78) – 2022 Guidelines on the Reference Lines for Use with Operational Carbon Intensity Indicators (CII Reference Lines Guidelines, G2)
- Resolution MEPC.354(78) – 2022 Guidelines on the Operational Carbon Intensity Rating of Ships (CII Rating Guidelines, G4)
- Resolution MEPC.355(78) – 2022 Interim Guidelines on Correction Factors and Voyage Adjustments for CII Calculations (CII Guidelines, G5)

eLearning - EEXI and CII Regulation Awareness.
This eLearning course will help delegates navigate the regulations and fully prepare for the requirements of EEXI and CII.
Find out more about this eLearning course.