Weights and Measures in the Roman World

Introduction

"Vinneus Valens served as a captain in the Imperial guard of the late lamented Augustus; he was in the habit of holding carts laden with cullei up in the air until they were emptied." (Pliny, Natural History VII.82)

The conversion factors between Roman and modern units are not easy to remember. The matter is complicated by the fact that scholars in Europe's main wine-producing countries always discuss relevant data on crop yields and consumption in metric terms (meters, liters, etc.), while writers in journals and books that cater to the American audience often present those data in the appropriately named U.S. System (miles, gallons, etc.).

Modern conversion factors:

1 U.S. gallon = 3.78 liters
1 U.S. pound = 454 grams
1 mile = 1.61 kilometers
1 acre = 0.00156 square miles = 4047 square meters
1 U.S. pint = 0.47 liters
1 U.S. ounce = 28.4 grams
1 inch = 2.54 centimeters