ISO 6578 “Refrigerated hydrocarbon liquids — Static measurement — Calculation procedure” has been released as a new version in October 2025 with the designation ISO 6578:2025.
This third edition cancels and replaces the second edition (ISO 6578:2017), which has been technically revised. As stated in the new version, the main changes are alignement with ISO 6976:2016 physical property data and calculation examples have been moved from the main body into an Annex.

In addition, calculation data in various Annexes are now designated as “informative” and not as “normative” any more. This apparently reflects the current global business practise of signing medium and long term LNG delivery contracts which contain various sets of calculation data for the revised Klosek-McKinley equation. QuantityWare BCG allows to define any customer specific data set for ISO 6578 LNG or LPG density calculations.

For LPG, the alternative density calculation models (Francis equation and COSTALD routine)  are not referenced any more.

Thus, QuantityWare BCG customers are in general in compliance with ISO 6578:2025 for their LNG & LPG implementations. In Q2 2026, a detailed online documentation update (PMC and GMC) will be delivered with a dedicated note. If customers wish a detailed analysis of their ISO 6578 implementations, contact your certified BCG consultant or ask for a QuantityWare Spot Consultancy.