CII calculator
Calculate a ship's attained Carbon Intensity Indicator (CII), the required CII and the A–E rating under MARPOL Annex VI regulation 28, and see how the rating moves as the requirement tightens up to 2030. Enter the annual figures reported under the IMO Data Collection System (DCS).
CII calculators by ship type
- Bulk carrier (DWT)
- Gas carrier (DWT)
- Tanker (DWT)
- Container ship (DWT)
- General cargo ship (DWT)
- Refrigerated cargo carrier (DWT)
- Combination carrier (DWT)
- LNG carrier (DWT)
- Ro-ro cargo ship (vehicle carrier) (GT)
- Ro-ro cargo ship (GT)
- Ro-ro passenger ship (GT)
- Ro-ro passenger ship — high-speed craft (SOLAS chapter X) (GT)
- Cruise passenger ship (GT)
How the CII is calculated
- Attained CII = total CO₂ emitted ÷ (capacity × total distance travelled), in grams of CO₂ per capacity-nautical mile (MEPC.352(78), amended by MEPC.412(84)). Capacity is DWT for cargo ships and tankers, GT for ro-ro, ro-pax and cruise ships.
- CO₂ = fuel mass × conversion factor CF for each fuel (MEPC.364(79)), summed.
- Reference CII = a × Capacity−c, the 2019 median line of the ship type (MEPC.353(78)).
- Required CII = (1 − Z/100) × reference CII, with the reduction factor Z for the year (MEPC.338(76), amended by MEPC.400(83)).
- Rating: the required CII times four factors gives the boundaries between A, B, C, D and E (MEPC.354(78)). Ships rated D for three consecutive years or E in one year must submit a corrective action plan.
Reduction factor Z
| Year | 2023 | 2024 | 2025 | 2026 | 2027 | 2028 | 2029 | 2030 |
|---|---|---|---|---|---|---|---|---|
| Z | 5% | 7% | 9% | 11% | 13.625% | 16.25% | 18.875% | 21.5% |
CO₂ conversion factors
| Fuel | CF (t CO₂ / t fuel) |
|---|---|
| Diesel / gas oil (MGO, MDO — ISO 8217 DMX–DMB) | 3.206 |
| Light fuel oil (ISO 8217 RMA–RMD) | 3.151 |
| Heavy fuel oil (ISO 8217 RME–RMK) | 3.114 |
| LPG — propane | 3.000 |
| LPG — butane | 3.030 |
| Ethane | 2.927 |
| LNG | 2.750 |
| Methanol | 1.375 |
| Ethanol | 1.913 |
What this calculator leaves out
It does not apply the correction factors and voyage adjustments of MEPC.355(78) (for example ice class, shuttle tankers, cargo heating, or periods excluded for safety reasons). Those can lower the attained CII of the ships they apply to. The official rating is issued by the flag Administration or recognized organization after DCS verification.