Marine fuel is commonly quoted by mass, but propulsion depends on usable energy. Lower calorific value (LCV) is often expressed in MJ/kg. Numerically, 1 MJ/kg equals 1 GJ per metric tonne, so an energy-basis comparison can divide the price per tonne by the LCV to estimate price per GJ.
For an illustration only, assume two offers both cost USD 600 per tonne. At 40.5 MJ/kg, the energy price is about USD 14.81/GJ. At 42.7 MJ/kg, it is about USD 14.05/GJ. The first offer is about 5.4% more expensive per unit of stated energy. These are explicit calculation assumptions, not current market quotes or evidence about a particular fuel lot.
The calculation is only a first comparison. Confirm whether values use LCV or higher calorific value, use a consistent laboratory or regulatory method, and consider engine efficiency, fuel quality, handling losses, and any operational limits. A declared or default energy value is not the same as a tested batch result.
Energy content and greenhouse gas performance must also stay separate. FuelEU Maritime combines energy use with prescribed well-to-wake emission factors and other rules. The EU ETS applies to covered reported emissions. A lower price per GJ does not prove lower lifecycle emissions, regulatory eligibility, or a lower total compliance cost.
The Verdaxis public energy calculator lets a user enter price, energy density, consumption, voyage, allowance-price, and coverage assumptions. Its price-per-GJ and voyage results are scenarios based on those inputs. They are not supplier quotes, verified laboratory results, or compliance determinations.