Required CII

The Required CII is the annual reference carbon-intensity value a ship must beat to avoid a poor rating. It is computed from a ship-type-specific 2019 reference line and a yearly reduction factor (the Z factor), so the bar tightens each year: 13.625, 16.25, 18.875, and 21.5 percent below the reference line for 2027 through 2030 under MEPC.400(83). The boundaries between the A-to-E bands are then set by fixed multipliers (dd vectors) around the required value, so a ship rated C sits near the required line and an A ship is well below it.