CII calculator: attained CII, required CII and rating
Enter a year's fuel and distance and see the ship's carbon intensity rating under MARPOL Annex VI, the required CII up to 2030 and how far it is from the next band.
Updated 2026-10-20
Calculate
What the CII is
The Carbon Intensity Indicator (CII) is the operational carbon rating under regulation 28 of MARPOL Annex VI. Since 1 January 2023 every bulk carrier, tanker, container ship, gas and LNG carrier, general cargo ship, refrigerated cargo carrier, combination carrier, ro-ro, ro-pax, vehicle carrier and cruise ship of 5,000 GT and above receives a rating from A to E each year, based on the fuel it burned and the distance it sailed. The Administration, or the recognised organisation acting for it, gives the rating in the Statement of Compliance after the IMO DCS data for the year are verified.
How the CII is calculated, in four steps
Step 1. CO₂ emitted in the year
FCj is the mass of fuel type j burned in the year and CF,j its carbon factor (table below).
Step 2. Attained annual operational CII (G1, MEPC.352(78))
In grams of CO₂ per tonne-mile (capacity-nautical mile). Capacity is deadweight for cargo ships and gross tonnage for ro-ro, ro-pax, cruise ships and vehicle carriers.
Step 3. Required CII (G2 MEPC.353(78), G3 MEPC.338(76) as amended)
| Year | 2023 | 2024 | 2025 | 2026 | 2027 | 2028 | 2029 | 2030 |
|---|---|---|---|---|---|---|---|---|
| Z (% below the 2019 reference) | 5% | 7% | 9% | 11% | 13.625% | 16.25% | 18.875% | 21.5% |
Step 4. Rating (G4, MEPC.354(78))
The attained CII is divided by the required CII and compared with four boundaries for the ship type. At or below the first boundary the ship is rated A; above the last it is rated E.
| Ship type | a | c | Capacity | Rating boundaries (× required CII: A/B, B/C, C/D, D/E) |
|---|---|---|---|---|
| Bulk carrier | 4,745 | 0.622 | DWT | 0.86 / 0.94 / 1.06 / 1.18 |
| Tanker | 5,247 | 0.61 | DWT | 0.82 / 0.93 / 1.08 / 1.28 |
| Container ship | 1,984 | 0.489 | DWT | 0.83 / 0.94 / 1.07 / 1.19 |
| General cargo ship | 31,948 | 0.792 | DWT | 0.83 / 0.94 / 1.06 / 1.19 |
| Gas carrier | 8,104 | 0.639 | DWT | 0.85 / 0.95 / 1.06 / 1.25 |
| Refrigerated cargo carrier | 4,600 | 0.557 | DWT | 0.78 / 0.91 / 1.07 / 1.20 |
| Combination carrier | 5,119 | 0.622 | DWT | 0.87 / 0.96 / 1.06 / 1.14 |
| Ro-ro cargo ship | 1,967 | 0.485 | GT | 0.76 / 0.89 / 1.08 / 1.27 |
| Ro-ro passenger ship | 2,023 | 0.46 | GT | 0.76 / 0.92 / 1.14 / 1.30 |
| Cruise passenger ship | 930 | 0.383 | GT | 0.87 / 0.95 / 1.06 / 1.16 |
Bulk carriers above 279,000 dwt use 279,000; LNG carriers, gas carriers, general cargo ships and vehicle carriers have size splits that the calculator applies.
Carbon factors
| Fuel | CF (t CO₂ per t fuel) | FuelEU well-to-wake default (gCO₂e/MJ) |
|---|---|---|
| Heavy fuel oil (RME to RMK) | 3.114 | 91.74 |
| Light fuel oil (RMA to RMD) | 3.151 | 91.39 |
| Diesel / gas oil (DMX to DMB) | 3.206 | 90.77 |
| LNG | 2.750 | 89.20 |
| Methanol | 1.375 | 103.15 |
What a D or E rating means
A ship rated D for three consecutive years, or E in a single year, needs a plan of corrective actions in its SEEMP Part III, showing how it will reach at least C. The plan is submitted with the attained CII and verified by the Administration or recognised organisation. How a SEEMP Part III and corrective action plan are prepared.
Calculation, estimate or verified rating?
This calculator works from the figures you enter. It does not apply the voyage adjustments and correction factors of G5 (MEPC.355(78)); the full calculator does, when you have the supporting records. If you only know the ship's name, the ship lookup gives an estimate from the EU MRV register. Only the Administration's Statement of Compliance is the verified rating.
Questions
How is the attained CII calculated?
Multiply each fuel burned in the year by its carbon factor to get the CO₂ emitted, then divide by the ship's capacity (deadweight, or gross tonnage for ro-ro, ro-pax, cruise ships and vehicle carriers) and by the distance sailed. The result is in grams of CO₂ per capacity-nautical mile.
What is the required CII for 2026?
The reference value for the ship type and size, reduced by Z = 11% in 2026. Z rises to 13.625% in 2027, 16.25% in 2028, 18.875% in 2029 and 21.5% in 2030.
Which ships need a CII rating?
Bulk carriers, tankers, container ships, gas and LNG carriers, general cargo ships, refrigerated cargo carriers, combination carriers, ro-ro, ro-pax and cruise ships and vehicle carriers of 5,000 GT and above, since 2023.
What happens if a ship is rated D or E?
A ship rated D for three consecutive years, or E in one year, must add a plan of corrective actions to its SEEMP Part III and have it verified.
Does this calculator apply the G5 correction factors?
No. It gives the uncorrected CII from your figures. The full calculator in the CarbonKeel app applies documented voyage adjustments and correction factors under MEPC.355(78).
EU ETS, FuelEU, CII and UK ETS for each ship, from the public register or your own data, with the reports for owners, charterers and lenders.