CII rating explained: what A to E actually means for a ship
Since 2023 ships of 5,000 GT and above of the types MARPOL Annex VI regulation 28 lists (bulk, gas, LNG, tanker, container, general cargo, refrigerated cargo and combination carriers, ro-ro cargo ships and vehicle carriers, ro-ro passenger and cruise passenger ships) get an annual carbon-intensity letter, A to E. The formula is simple; the consequences are increasingly commercial rather than regulatory.
The math in one paragraph
Attained CII = CO₂ emitted in the year ÷ (capacity × distance sailed), in grams of CO₂ per capacity-mile; capacity is the deadweight, or the gross tonnage for ro-ro and passenger ships. It is compared against a required value that tightens every year (reduction factors stepped from 5% in 2023 toward 11% in 2026 against the 2019 reference). Type-specific boundaries then place the ratio into A, B, C, D or E.
What D and E trigger
A single E, or three consecutive D ratings, requires a corrective action plan added to the ship’s SEEMP Part III and verified. There is no fine attached, but that is not the same as no consequence: under MARPOL Annex VI reg. 6.8 the flag State or recognised organisation withholds the DCS/CII Statement of Compliance until the plan is in place and verified — and a ship without a current Statement is a port State problem, not an administrative one.
The known quirk: a ship that sails little but keeps burning fuel in port or at anchor collapses its denominator and can rate D/E despite low absolute emissions — idle time is data worth watching for exactly this reason.
The commercial weight of the letter
Charterers increasingly write CII clauses (BIMCO published a standard one), banks reference efficiency data under the Poseidon Principles, and published MRV data makes a ship’s footprint visible to counterparties. The letter travels further in negotiations than in enforcement.
The data behind these rules, handled for you.
BunkerIstanbul prepares EU MRV, IMO DCS, EU ETS and FuelEU figures and an indicative CII from the noon reports and BDNs your crew already logs — alongside competing bunker quotes from suppliers approved by our team. Free for shipowners.
Frequently asked questions
Which ships get a CII rating?
Ships of 5,000 GT and above of the types MARPOL Annex VI regulation 28 lists: bulk, gas, LNG, tanker, container, general cargo, refrigerated cargo and combination carriers, ro-ro cargo ships and vehicle carriers, ro-ro passenger and cruise passenger ships. Tugs, offshore and other types are outside it, as are smaller vessels, even where EU MRV now covers them.
Can a rating be improved within the year?
The rating is computed on the full calendar year, so what moves it is the remaining months: speed and routing choices, port time, hull condition, utilisation. Our public calculator projects the same fuel pattern across coming years’ tightening limits.
Is CII connected to EU ETS or FuelEU?
They share the underlying fuel data but are independent regimes: CII is an IMO efficiency letter, EU ETS prices the CO₂, FuelEU limits the GHG intensity of the energy used.