Estimate a ship's operational Carbon Intensity Indicator and its A–E rating from the year's fuel, distance and deadweight. It uses the IMO reference lines and rating boundaries. A planning estimate — the verified rating comes from the vessel's reported DCS data.
The attained CII is the year's CO&sub2; divided by deadweight times distance (the AER). The required CII is the IMO reference line for the ship type, reduced by the year's factor — 5% in 2023 rising to 11% in 2026. The ratio between them sets the band.
A ship must sit at C or better. Three consecutive years at D, or a single E, triggers a corrective action plan in the SEEMP. Watching the trend mid-year is what lets you slow down or re-plan before the rating is locked in.
Reference lines from IMO MEPC.353(78); rating boundaries from MEPC.354(78). Bulk carrier, tanker, container and general-cargo types are covered.