Roman Measurements

Measures of Capacity
Romans measured dry capacity (grain) by the MODIUS (8.75 litres or 1.1 peck; by weight just over 6-2/3 kilograms or 14-2/3 lbs.) and wet capacity (oil and wine) by the AMPHORA (26 liters or nearly 7 gallons). The amphora was three times the volume of the modius. In markets, oil and wine were usually cited by the sextarius (0.539 litres or just under 1 pint).
Dry and Liquid Measures
1 Modius = 16 Sextarii
1 Culleus = 20 Amphorae
1 Sextarius = 16 Cyathi
1 Amphora = 48 Sextarii

In the Price Edict (301), Diocletian priced many items by the MODIUS CASTRENSIS ("camp modius"), equivalent to 1.5 modii.
Greeks measured grain by the MEDIMNOS (25 kilgrs. or 55 lbs.), equal to 6 Roman modii. In Egypt grain was measured by the ARTABA (18.75 kilgrs. or 41.3 lbs.), equal to 4.5 modii. Greeks measured wet capacity by the METRETES, divided into 12 choes = 144 kotylai = 864 kyathoi. The KOTYLE was half of the Roman SEXTARIUS.
In the Principate, an adult male required 4 modii as his monthly ration of wheat, which probably represented two-thirds of his caloric intake (with oil, vegetables, and protein making up the other third). The Roman soldier was allotted 1 cyathus (1/16 sextarius) of olive oil and 1 to 2 sextarii of wine per day. A peasant family of four consumed an annual minimum of 120 modii of wheat, 120 sextarii of olive oil, and possibly 720 sextarii of wine (often mixed with vinegar as posca).

Measures of Area
Romans measured area by the amount ploughed in a day by a yoke of oxen. Land was reckoned by the IUGERUM (28,000 square Roman feet or 5/8 of an acre). A farm of 10 iugera (5-6 acres or 2.5 hectares) could provide a plebian family of most of its annual subsistence needs. In Egypt, land was measured by the AROURA (equal to 1.1 iugera). 
Measures of Distance 
Romans measured distance by the mile, mille passuum ("one thousand of paces"), equivalent to 1,620 English yards or 92% of the English mile. 1 Roman mile = 1,000 paces (passus) = 5,000 feet (pedes). An average day's march for a Roman army was 15 to 17 miles; a forced march (magnum iter) was 20 to 25 miles. 
 

The Roman Era