BELLBOOK TOOLS / 01

Your ship’s CII,
by the numbers.

Estimate a rating from annual fuel use and distance,
then compare the targets ahead.

Ship & annual activity

Enter complete records for 1 January–31 December of the selected year.

1. Check your ship

Ship typeActivity yearGross tonnage (GT)

For covered ships of at least 5,000 GT. Confirm Convention applicability beyond tonnage and ship type.

Fuels consumed

Confirm the ship type and fuels before calculating.

2. Enter annual records

Where to find the inputs

GT: use gross tonnage from the International Tonnage Certificate.
DWT: use deadweight from approved ship particulars, not the cargo actually carried.
Distance: reconcile the annual DCS total with voyage logs and check that the unit is nautical miles (nm).
Fuel: use annual consumption by fuel type from DCS records, in tonnes (t), not bunker deliveries or tank balances.

Deadweight tonnage (DWT)Annual total distance (nm)

Include distance both under way and not under way. Do not substitute cargo carried or laden distance alone.

Annual fuel consumption

Tonnes · Enter 0 for unused fuels

HFO · Heavy fuel oil

CO₂ conversion factor 3.114LFO · Light fuel oil

CO₂ conversion factor 3.151Diesel / Gas oil

CO₂ conversion factor 3.206

Fossil oils only. LNG, LPG, methanol, biofuels, G5 corrections and voyage adjustments are not included.

This tool provides an unadjusted estimate based on your inputs for reference. It does not replace official CII verification or reporting, legal advice, or a determination of regulatory compliance. Full disclaimer

YOUR CII ESTIMATE

Unadjusted estimate

3. Result and next steps

Enter your ship’s data
to see the result here.

To try a worked case,
choose “Load example”.

BEHIND THE NUMBER

Follow the calculation.

From inputs to result

Same activity, changing annual targets

A comparison holding fuel, distance and capacity constant. It is not a forecast of future operations.

Same-activity CII comparison through 2030
Year	Reduction	Required CII	Est. rating

Show rating boundaries for the selected year

Display values use up to 6 decimals. Calculations and CSV retain full precision. Numerical equality with a boundary shows both adjacent grades.

METHOD & GUIDANCE

The method is part of the result.

Multiply each fuel’s consumption by its CO₂ conversion factor, add the emissions, then divide by ship capacity times annual total distance. Compare with the required CII and ship-type rating boundaries for the selected year.

This tool calculates DWT-based AER or GT-based cgDIST. Do not substitute a similar ship type for an unsupported one.

Scope: the 8 listed ship types, 2026–2030, fossil HFO, LFO and diesel/gas oil. Actual CII must account for all consumed fuels. Results are incomplete for ships using unsupported fuels.

Read the CII example and reporting guidance →Review SEEMP corrective actions after D or E →

Official IMO documents

Method reviewed 2026-09-28
G2 reference lines · G3 annual reductions · G4 rating boundaries