CII Rating Calculator for Ships

Ship Universe Maritime Tool

CII Rating Calculator for Ships

Calculate attained CII, required CII and the IMO A to E Carbon Intensity Indicator rating using ship type, capacity, annual distance and fuel consumption or verified CO2 emissions. The tool also shows C-rating headroom, fuel reduction estimates and the rating outlook through 2030.

Attained CII

Annual CO2 divided by capacity x total distance travelled

Required CII

2019 ship-type reference line adjusted by the annual reduction factor

Rating

A, B, C, D or E using IMO ship-type rating-boundary vectors

Ship & Reporting Year

Select the IMO ship type, reporting year and the capacity used by the CII framework.

Ship type

Reporting year

Deadweight

DWT

Total distance travelled

nm/year

Use total distance reported under IMO DCS. Under the 2026 G1 amendment, this includes distance travelled both under way and not under way.

Annual Fuel & CO2

The fuel-to-CO2 factor is editable. Use the actual underlying fuel grade, not sulfur content alone.

Fuel type

Annual fuel consumed

MT/year

CO2 conversion factor

tCO2/MT

Verified CO2 override (optional)

tCO2/year

If entered, this value replaces fuel-derived CO2 in the attained CII calculation.

Ship & Reporting Year

Advanced mode supports multiple fuels plus an optional verified CO2 override.

Ship type

Reporting year

Deadweight

DWT

Total distance travelled

nm/year

Use the total annual distance reported under IMO DCS.

Fuel Mix

Enter up to four fuel quantities. Conversion factors are editable planning defaults.

Fuel

Consumed MT

CF tCO2/MT

Verified CII Inputs

Use the override only when you already have a verified or properly adjusted annual CO2 value for CII.

Verified annual CO2 override

tCO2/year

Planning fuel-change scenario

% CO2

Optional. Negative values model lower annual CO2 for the scenario results only.

CII Rating Results

Simple annual CII calculation

Enter ship data

Enter ship type, capacity, annual distance and annual fuel consumption to calculate attained CII, required CII and the A to E rating.

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Operational Carbon Intensity Rating

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Attained CII

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gCO2/(DWT nm)

Required CII

—

For selected reporting year

CII / Required Ratio

—

C Upper Boundary

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Annual CO2 Used

—

Reference-Line Capacity

—

CO2 Headroom / Overage to C

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CO2 Reduction Needed for C

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Proportional Fuel Reduction to C

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CO2 Reduction to Next Better Grade

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2030 Rating at Same Operations

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2030 Reduction Needed for C

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Rating Boundaries

CII Calculation Summary

Rating Outlook Through 2030 Assumes same annual CO2 and distance

Year	Reduction Z	Required CII	C Upper	Rating	CO2 Change to C

CII note: Rating guidance will appear here after calculation.

Regulatory basis: the calculator uses the IMO supply-based CII formula, 2019 ship-type reference-line parameters, A to E rating vectors, the amended 2027-2030 reduction factors, and the 2026 clarification that total distance travelled includes both under-way and not-under-way distance. It does not automatically apply G5 correction factors or voyage adjustments.

Planning estimate only. This calculator is not a substitute for the verified attained annual operational CII, Statement of Compliance, SEEMP Part III, Administration or recognized-organization verification. Actual CII can depend on verified IMO DCS data, eligible correction factors and voyage adjustments, fuel-specific documentary evidence, ship classification and subsequent IMO amendments. A ship rated D for three consecutive years or rated E is subject to corrective-action requirements under the CII framework. Confirm the official calculation before compliance decisions.

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