Maritime Decarbonization & ESG Operations
IMO Shipping CII Rating, AER & EEOI Carbon Formula
Calculate IMO MARPOL Annex VI Attained Annual Efficiency Ratio AER (g CO2 / DWT-nm), Voluntary Operational EEOI (g CO2 / cargo-ton-nm), CII Compliance Ratio, and A-to-E Rating Band.
Never confuse mandatory capacity-based AER with cargo-based EEOI in IMO CII audits!
Under IMO MARPOL Annex VI (MEPC.352(78) & MEPC.354(78)), cargo vessels >= 5,000 GT receive an annual A-through-E Carbon Intensity Indicator (CII) rating based on Annual Efficiency Ratio AER = (Fuel_MT * CF_CO2 * 1,000,000) / (Vessel_DWT * Annual_Distance_nm), measured in grams of CO2 per deadweight-ton-nautical-mile using static summer DWT capacity on EVERY leg (including empty ballast voyages)! By contrast, Sea Cargo Charter / IMO voluntary Energy Efficiency Operational Indicator EEOI = (Fuel_MT * CF_CO2 * 1,000,000) / (Mean_Cargo_MT * Annual_Distance_nm) divides by ACTUAL cargo mass transported—so on a 60% laden/ballast bulk cycle, EEOI equals AER / 0.60 and penalizes empty ballast positioning whereas AER does not!
Verify on Annual_HFO_Burn = 6,000 MT (B2), IMO_CO2_Factor CF = 3.114 t-CO2/t-fuel (official HFO factor, B3 -> 18,684,000,000 g CO2), Vessel_DWT = 100,000 DWT (B4), Annual_Distance = 60,000 nm (B5 -> 6.0e9 DWT-nm), Mean_Cargo_Carried = 60,000 MT (60% cycle utilization, B6), and Required_CII_Benchmark = 3.20 g/(DWT-nm) (B7): Attained AER is 18.684e9 / 6.0e9 = 3.114 g/(DWT-nm) (E2); Operational EEOI is 18.684e9 / 3.6e9 = 5.190 g/(cargo-t-nm) (E3); CII Ratio Attained / Required is 3.114 / 3.20 = 0.9731 (E4); and Bulk-Carrier Rating Band (<=0.86 A, <=0.94 B, <=1.06 C, <=1.18 D, >1.18 E) is "Rating C (Moderate Compliant)" (E5)!
| IMO MARPOL Annex VI Metric (6,000t HFO @ CF=3.114, 100k DWT, 60k nm, 60k Cargo, Req=3.20) | Formula | Verified Output |
|---|---|---|
| Attained Mandatory AER | (Fuel * CF * 10^6) / (DWT * Dist_nm) | 3.114 g CO2 / (DWT * nm) |
| Operational Voluntary EEOI | (Fuel * CF * 10^6) / (Cargo * Dist_nm) | 5.190 g CO2 / (t-cargo * nm) |
| CII Compliance Ratio | Attained_AER / Required_CII | 0.9731 (0.7161 on LNG) |
| IMO Annual CII Rating (A–E) | Bulk Carrier d1..d4 Thresholds | Rating C (Moderate Compliant) |
IMO Attained AER & CII Compliance Ratio Formula
Validate Fuel_MT > 0, CF > 0, 0 < Mean_Cargo_MT <= Vessel_DWT, Distance_nm > 0, and Required_CII > 0!
=LET(fl_t, B2, cf_c, B3, dw_t, B4, ds_n, B5, cg_t, B6, rq_c, B7, IF(OR(fl_t <= 0, cf_c <= 0, dw_t <= 0, ds_n <= 0, cg_t <= 0, cg_t > dw_t, rq_c <= 0), "Invalid IMO Noon Log", LET(ae_r, (fl_t * cf_c * 1000000) / (dw_t * ds_n), ROUND(ae_r / rq_c, 4))))IMO Five-Band CII Rating Classifier (A through E)
Test dual-fuel LNG retrofit (Fuel = 5,000 MT, CF = 2.75 -> Ratio 0.7161 "Rating A") vs hull-fouled speed-up (Fuel = 7,800 MT HFO -> Ratio 1.2651 "Rating E", triggering immediate SEEMP Part III corrective action)!
=IF(ISTEXT(E4), E4, IF(E4 <= 0.86, "Rating A (Major Superior)", IF(E4 <= 0.94, "Rating B (Minor Superior)", IF(E4 <= 1.06, "Rating C (Moderate Compliant)", IF(E4 <= 1.18, "Rating D (Corrective Plan @ 3 Yrs)", "Rating E (Immediate SEEMP Action)")))))Try the example
Use the original values or change them to test your understanding.