Free CII Calculator
Work out your ship’s Carbon Intensity Indicator (CII) and A–E rating in seconds. Enter vessel type, deadweight, distance and fuel burned — no account needed.
Your vessel & voyage data
Fuel consumed (metric tonnes)
Your result
Same fuel, same distance: the rating slips as the IMO required line tightens every year. This is why owners track CII continuously, 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.
Track CII automatically across every voyage, get verifier-ready DCS and EU MRV reports, and see your whole fleet at a glance — free for shipowners.
What is the CII rating?
Carbon Intensity Indicator
Since 2023 every cargo and passenger ship of 5,000 GT and above must report an annual CII — the CO₂ it emits per tonne of capacity per nautical mile — and receive an A to E rating under IMO MARPOL Annex VI.
How it is calculated
Attained CII = total CO₂ (from fuel burned × IMO carbon factors) divided by deadweight × distance sailed. 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?
Cargo, RoPax and cruise ships of 5,000 GT and above on international voyages, under IMO MARPOL Annex VI. Smaller ships are outside CII but may fall under EU MRV from 2025 (400–5,000 GT general cargo).
Is this calculator accurate?
It uses the same IMO MEPC reference lines, reduction factors and carbon factors as our full platform, so the rating logic matches. It is an estimate for planning; your official CII is calculated 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 automatic, saved CII tracking across your voyages.