The sextarius was an ancient Roman unit of measurement used primarily for liquids, equivalent to about 0.5 liters or roughly 0.13 gallons. It was part of the Roman system of weights and measures, which included other units like the modius for dry goods. The sextarius was commonly used in trade and daily life, especially for measuring wine and oil. In addition to its use in commerce, the sextarius also played a role in Roman law and regulations regarding food and drink. It was often referenced in legal texts to define quantities for rations or portions, ensuring fair distribution among citizens and soldiers.