Ballast-Leg Correction

Many voyages are laden out, ballast back. This calculator computes the round-trip CO₂ intensity per tonne-nm of cargo delivered, which is usually a better comparator than a single-leg AER or EEOI.

VoyageEEOI

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This calculator requires JavaScript to compute its result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

\text{EEOI}_\text{rt} = \frac{(F_\text{laden} + F_\text{ballast}) \cdot C_f \cdot 10^6}{m_\text{cargo} \cdot d_\text{laden}}

Symbol	Meaning	Unit
$\text{EEOI}_\text{rt}$	Round-trip Energy Efficiency Operational Indicator	g CO₂ / (t cargo · nm)
$F_\text{laden}$	Fuel burned on the laden leg	t
$F_\text{ballast}$	Fuel burned on the ballast leg	t
$C_f$	CO₂ conversion factor for the fuel	t CO₂ / t fuel
$m_\text{cargo}$	Cargo mass delivered	t
$d_\text{laden}$	Distance of the laden leg	nm
$10^6$	Tonnes → grams

Source: IMO MEPC.1/Circ.684 - EEOI guidelines; IMO MEPC.364(79) - Cf factors

In short

Round-trip EEOI attributes the ballast-leg fuel to the cargo-nm of the paired laden leg - a fairer comparator than per-leg AER.

Learn the theory Voyage Estimation: TCE, Bunkers, and Canal Economics