Solidus

The gold coin of the Roman and Byzantine Empire

The solidus (Latin solidus) was a gold coin introduced by the emperor Constantine in the 4th century AD. replacing the aureus. Its introduction marked one of the most important monetary reforms of antiquity, guaranteeing stability to the imperial economic system.

The solidus had a weight of approximately 4.5 grams, equal to 1/72 of a Roman pound, and maintained remarkable consistency over time in both the weight and purity of the gold. This stability made it a reference currency in international trade for several centuries.

solidus front solidus rear
Roman solidus, front Roman solidus, reverse

The role in the Byzantine system

The solidus became the basis of the coinage of the Byzantine Empire, maintaining a central role until the 10th century. Thanks to its reliability, it was widely used even outside the imperial borders, influencing numerous European and Mediterranean monetary systems.

Among its fractions were the semis (half solidus) and the tremisse (one third of solidus), used to facilitate smaller payments.

Byzantine solidus front solidus byzantine reverse
Byzantine solidus, front Byzantine solidus, reverse

From solidus to the Carolingian system

The solidus does not directly belong to the Carolingian system, but represents an important historical bridge between Roman and medieval coinage.

In the Carolingian system, the term soldo derives from the solidus, although in most cases it remained a unit of account rather than an actually minted coin.

This terminological continuity demonstrates how the medieval monetary structure is deeply rooted in the Roman and Byzantine legacy.

Related pages

Essential data

MetalGold
WeightApproximately 4.5g
Ratio1/72 of a Roman pound
PeriodFrom the 4th century AD