The Carbon Intensity Indicator (CII)
The CO2-Label for Ships.

The Carbon Intensity Indicator (CII) is the new energy label set to rewrite the future of shipping. It obliges shipping companies to map their emissions in order to reduce the total CO2 output of the entire sector. Read here how your ship or fleet will be assessed, what the direct consequences are if you do not meet the required rating, and also how you can record your emissions very accurately with a relatively small technical adjustment.
Takeaways from this article
  • About CII: The CII is a new IMO system that gives ships an annual CO2 score (A to E) to measure their environmental efficiency.
  • The calculation: The score is calculated by dividing the total CO2 emission by the transport performance, taking the type of ship into account.
  • The requirements: Ships must achieve a minimum C rating; poor scores (E or repeated D) require mandatory, approved improvement plans.
  • The impact: A poor rating has economic consequences, such as rejection by charterers, a decrease in the ship’s value, and a potential sailing ban.
  • The solution: Discover our Smart Solution Fuel Measuring System with which you can easily map fuel consumption and emissions.
Don’t feel like reading it all?
Then…

What is CII?

The Carbon Intensity Indicator (CII) is a new regulation to reduce ship CO2 emissions. The goal is to gradually lower the total environmental impact of the maritime sector. This CII regulation was officially adopted by the IMO in June 2021 (during the 76th session of the Marine Environment Protection Committee, or MEPC 76) and came into force on January 1, 2023.

The IMO (International Maritime Organization) is the specialized agency of the United Nations responsible for the safety and security of shipping and the prevention of marine and air pollution by ships.

The CII regulation is part of the IMO’s short-term measures to reduce the carbon intensity of international shipping by at least 40% by 2030 compared to 2008 levels.

Currently (Q4-2025), the CII only applies to cargo and cruise ships larger than 5,000 GT (Gross Tonnage). However, it is suspected that this will be extended to other types of ships over time – including inland waterways vessels.

CII rating - official infographic - IMO

How is the CII value determined?

Each year, a ship must calculate its Attained CII (achieved CII value). The formula for this is the total annual CO2 emissions divided by the transport capacity multiplied by the total distance sailed that year

Total fuel consumption
_____________________________

( transport capacity X total distance sailed in nautical miles )

Total fuel consumption
_____________________________

( transport capacity X total distance sailed in nautical miles )

The Attained CII is then compared with an IMO Required CII (the necessary CII value). The difference between these two values subsequently determines the carbon intensity rating.

The CII Rating (Classification)

Based on the calculated CII value, each ship receives an environmental rating from A to E: You can compare this to an Energy Performance Certificate for houses or the energy label for electrical appliances.

  • A. Major Superior: Very efficient and much better than the required standard.
  • B. Minor Superior: Good performance, better than the standard.
  • C. Moderate: Meets the minimum standard (this rating is required).
  • D. Minor Inferior: Below the minimum standard.
  • E. Inferior Performance: Poor performance, far below the standard
Carbon Intensity Indicator - CII regeling voor schepen - visual Intercontrol

KRAL Smart Solution – the Smart Fuel Measuring System

KRAL Smart Solution
Our KRAL Smart Solution is the reliable solution for measuring and registering the fuel consumption and emissions of your ship or fleet!
Among others, these organizations already rely on our Smart Solution
acta marine
DNV-GL

The Catch in the Calculation

Be aware; it is still slightly more nuanced; the IMO distinguishes between two categories. On the one hand, the category of cruise and RoRo ships, and on the other hand, the category including bulk & LNG carriers, container ships, cargo ships, and tankers. And for each category, it uses a slightly different calculation to determine the CII value.

How is the Attained CII really calculated?

The Attained CII is calculated by dividing the total mass of CO2 emitted by a ship by the total transport work in that year. The transport work is calculated using data from the IMO Data Collection System (IMO DCS)

For the Cruise and RoRo ship category, the capacity gross ton Distance (cgDIST) is used for the calculation. However, for ships in the other category, the Annual Efficiency Ratio (AER) is used instead.

cgDIST and AER use different capacity data:

  • cgDIST uses the total annual fuel consumption, the number of nautical miles sailed, AND the gross tonnage (GT) of the ship.
  • AER uses the total annual fuel consumption, the number of nautical miles sailed, AND the deadweight tonnage (DWT) of the ship.

Which measure (DWT or GT) is used, therefore depends on the ship type. We have tried to simplify that below..

Carbon Intensity Indicator (CII) berekenen - Intercontrol
Cruise & RoRo Ships

Total fuel consumption
_____________________________

( gross tonnage (GT) X total distance sailed in nautical miles )

Tankers, Carriers, Container & Cargo Ships

Total fuel consumption
_____________________________

( deadweight tonnage (DWT) X total distance sailed in nautical miles )

Carbon Intensity Indicator (CII) berekenen cruise-schip
Cruise & RoRo Ships

Total fuel consumption
_____________________________

(gross tonnage (GT) X total nautical miles)

Carbon Intensity Indicator (CII) berekenen voor een containerschip
Tankers, Carriers, Container & Cargo Ships

Total fuel consumption
_____________________________

(deadweight tonnage (DWT) X total nautical miles)

We collaborate with

Onboard is a Dutch technology company that aims to digitize the maritime sector by linking ships, crew, and shore operations to the cloud and the supply chain.

Our KRAL Smart Solution provides Onboard with all the data regarding consumption and emissions.

What if your ship fails to comply due to a D or E rating?

Ships that

  • Receive a D rating for three consecutive years, OR
  • Receive an E rating for one year,

must adjust their Ship Energy Efficiency Management Plan (SEEMP – Part III). This plan must then contain an improvement plan to raise the CII rating. Without an approved plan, the ship will not receive a Statement of Compliance (SoC) and may potentially not be allowed to sail.

The CII compels shipowners to modernize their ships faster, for example by optimizing speed, saving fuel, or switching to cleaner fuels.

What are the repercussions for non-compliance?

The CII is an operational measure whereby every ship above 5,000 GT receives an annual score, ranging from A (best) to E (worst). Ships with a rating of C or better are considered compliant.

The sanctions for achieving a poor score are primarily corrective measures rather than direct financial penalties (as is the case with the EU’s FuelEU Maritime regulation). However, this does not negate the fact that there will likely also be negative financial consequences arising from the market.

Mandatory Corrective Actions from the IMO

If a ship achieves a score that is too low, the following mandatory steps come into effect:

  • E-rating (one year): The ship must immediately draw up an action plan with corrective measures.
  • D-rating (three consecutive years): The ship must also draw up an action plan with corrective measures.

This action plan must be included in Part III of the Ship Energy Efficiency Management Plan (SEEMP) and must demonstrate how the ship intends to achieve the required C-rating (or better). This updated SEEMP must be verified before the ship’s Statement of Compliance (SoC) can be issued.

  • The ultimate consequence: If a ship fails to have the required SEEMP Part III (including the corrective action plan), the validity of the SoC (Statement of Compliance) may be compromised. A ship without a valid SoC theoretically risks being detained by Port State Control, which prevents it from sailing.

Commercial and Financial Consequences from the Market

These are the most direct and severe consequences of a poor CII rating:

  • Chartering Decisions: Charterers committed to sustainability will avoid ships with a D or E rating and will favor ships with an A or B rating. This can lead to a market with “tiered” rates (more expensive A/B ships, cheaper D/E ships) and fewer assignments for less efficient vessels.
  • Ship Value: A poor CII rating can affect the market value of the ship upon sale or purchase.
  • Financing and Insurance: Banks and insurers may charge higher costs or offer more favorable terms to ships with a better rating (A or B), as these are considered a lower risk.

In short, although the IMO primarily enforces improvement through documentation and planning, the commercial market and partners enforce compliance through economic pressure.

KRAL Smart Solution
The solution for the Carbon Intensity Indicator (CII) regulation.

The CII rating is directly determined by the reliability of the reported emissions. Without verified, accurate fuel data, you risk a rating that is worse than the reality, purely due to the use of estimated data.

Our Smart Solution Fuel Measuring System assists shipping companies with cost control, compliance with emissions regulations, and making consumption costs transparent.

The accuracy of your CII rating thus stands or falls with the quality of your data. And where many CII reports are still based on estimated consumption data, the KRAL Smart Solution transforms the CII calculation from an estimate into a verified fact.

This measuring system delivers not just a volume, but directly the compensated fuel mass—the crucial variable for the CII formula. With this verified and auditable measurement, you are assured of an Attained CII value that exactly reflects the actual efficiency of your ship.

Yes, I want accurate insight
into my fuel consumption, oil flows, and emissions!

The Smart Solution Advantages:

Direct CII Impact & Financial ROI
By measuring the mass of fuel in real-time and temperature-compensated (instead of volume), the KRAL Smart Solution eliminates measurement errors. This ensures that the reported CII score exactly matches the actual efficiency of your ship. The result:

  • Better CII Rating: A higher CII rating (A or B) is direct commercial capital.
  • Reduced Risk of D/E Rating: You avoid mandatory, expensive corrective measures and the risk of rejection by charterers.
  • Optimization: Real-time data enables precision interventions in the SEEMP (improvement plan), maximizing fuel savings.

Even more advantages

  • Multi-Engine Capacity: It can process and collect the measurement values from up to 32 flowmeters simultaneously via a single cable.
  • Accuracy under Difficult Conditions: The system accounts for complex conditions in the pipes, such as pump pulsations, fluctuating flow direction, and temperature differences, for an accurate measurement.
  • Easy Installation (Retrofit): Thanks to the ‘unit-to-unit’ loop-through method of the single cable, installation (especially for subsequent installation or retrofit) is significantly simplified, saving time and costs.
  • Integrated Data Processing: The calculation unit directly on the flowmeter ensures analysis of sensor signals (including flow direction detection and temperature compensation) and the direct determination of the mass value.
  • Open Structure: The system operates with an open Modbus structure, allowing it to be easily connected to existing on-board monitoring systems.
DNV-GL
These organizations also rely on our Smart Solution
Damen
Joedood Marine Group

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