Modius

Ancient RomanHistorical unit (no longer in standard use)Approximate value

Sixteen sextarii, about 8.73 L. The standard Roman dry measure, used for grain.

1 modius = 8.733333333 liters (approximately).

Approximate value. Standards for the modius varied by place and period, so this converter uses the most commonly cited value. Treat results as estimates, not exact figures.

About the modius

Grain, not wine, was what the modius measured. It belonged to the Roman dry scale, where it stood at the top of the ordinary series, with the semimodius at half its size and the larger modius castrensis, about 12.93 L, above it. Wikipedia's table gives the plain modius as 8.73 L, the figure used here, and describes it as 2 and two thirds congii or 16 sextarii.

That puts it at one third of an amphora quadrantal, so liquid and dry measures shared a single system built on the cubic Roman foot. Because it is a multiple of the sextarius, the usual uncertainty applies: surviving vessels suggest the sextarius ranged from 500 to 580 mL, which would put the modius between roughly 8.0 and 9.3 L. A bronze modius stamped with a reference to imperial regulation of weights and measures survives, which shows that the state tried to keep the size fixed. Today it is a little under a quarter of a US bushel.

Sources: Wikipedia: Ancient Roman units of measurement

Modius conversion chart

1 modius expressed in every other volume unit:

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