Free CII Calculator
Work out your ship’s Carbon Intensity Indicator (CII) and estimate its A–E band in seconds. Enter vessel type, deadweight or gross tonnage, distance and fuel burned — no account needed.
Your vessel & voyage data
Fuel consumed (metric tonnes)
Your result
Same fuel, same distance: the band slips as the IMO required line tightens every year. This is why owners follow CII through the year, not once a year.
Estimate for planning only — not verification or legal advice. Official CII is reported through IMO DCS and your verifier.
This is a one-off estimate.
See your ships’ year-to-date indicative CII from the noon reports your crew already files, get DCS and EU MRV reports prepared for your verifier, and see your whole fleet at a glance — free for shipowners.
What is the CII rating?
Carbon Intensity Indicator
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) report an annual CII — the CO₂ emitted per unit of capacity per nautical mile — and receive an A to E rating from their flag State or its recognised organisation, under IMO MARPOL Annex VI.
How it is calculated
Attained CII = total CO₂ (from fuel burned × IMO carbon factors) divided by capacity × distance sailed; capacity is the deadweight, or the gross tonnage for ro-ro and passenger ships. It is compared against a required CII from the IMO MEPC reference line for your ship type, tightened each year.
What A–E mean
C is the minimum to stay compliant. Three consecutive D ratings, or a single E, trigger a mandatory corrective action plan in your SEEMP. The required line drops every year, so today’s C can become tomorrow’s D.
Frequently asked questions
Which ships need 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 ships; EU MRV covers general cargo ships of 400–5,000 GT from 2025.
Is this calculator accurate?
It uses the same IMO reference lines, reduction factors, rating boundaries and carbon factors as the BunkerIstanbul platform. The platform records VLSFO, HSFO, LSMGO and MGO; LNG can be entered here only. It is an estimate for planning: correction factors are not applied, and the official rating is given by the flag State or its recognised organisation from verified DCS data.
Which fuels are supported?
VLSFO, LSMGO, HSFO, MGO and LNG, each with its IMO CO₂ conversion factor. Enter tonnes consumed over the year for the vessel.
Do you store my data?
No. This calculator runs entirely in your browser and saves nothing. Create a free account only if you want your ships’ year-to-date indicative CII worked out from their noon reports.