DENOMINATIONS of the Roman Empire

GOLD Coins

Aureus
The aureus was the main gold coin of the Early Empire, and its minting was under the direct control of the Emperor. Under Augustus, the currency was such:
  1 aureus = 25 denarii
1 quinarius (gold) = 12 1/2 denarii
1 denarius = 16 asses
1 quinarius (silver) = 8 asses
1 sestertius = 4 asses
1 dupondius = 2 asses
1 as = 4 quadrantes
1 semis = 2 quadrantes
1 quadrans = 1/4 as
Solidus
Constantine introduced a new gold coin in his reign, to replace the aureus, which was called the solidus and was 1/72 of a pound.
Image Not Yet Available Scripulum
This was another gold denomination introduced by Constantine, worth 1 1/2 of a
solidus.
Image Not Yet Available Semissis
was a smaller gold coin introduced by Constantine, and was worth 1/2 of a
solidus. It was replaced in the reign of Theodosius I.
Tremissis
The tremissis was introduced by Theodosius I to replace Constantine's
scripulum, and was worth 1/3 of a solidus.

SILVER Coins

Denarius
The denarius was the main silver coin, in fact the main denomination, of the Roman Republic. Under the Empire, Augustus controlled the minting of the gold and silver denominations, and the denarius continued. Under Nero the weight and fineness of the denarius dropped, and this cost-cutting practice was continued under successive emperor. By the reign of Caracalla, the denarius was about 40% silver, and the new
antoninianus was introduced. The denarius continued, but was gradually phased out, first becoming bronze, and then disappearing after serving the Romans for almost 400 years.
Quinarius
Silver quinarii, or half denarii, were minted sporadically throughout the Republic. Its minting became more regular under the Early Principate and, under Augustus, it was worth 8 asses.
Antoninianus
This coin was introduced by Caracalla and worth twice that of the
Denarius, but it actually only had about 1 1/2 of the denarius's silver content. Both the Antoninianus and the denarius continued for some time until the denarius was phased out. Gradually, over the Third Century, the silver content of the antoninianus dropped, until it was merely silver washed bronze coins. At this time, it is considered to be an AE coin.
Image Not Yet Available Argenteus
This silver coin was first minted by Diocletian as part of his monetary reforms. It lasted until the reign of Constantine and replaced the old denarius, for it was roughly the same fineness and weight of the early denarius.
Image Not Yet Available Miliarense
This silver coin was worth 1/18 of a
solidus, and was introduced by Constantine late in his reign to replace the argenteus.
Siliqua
Another silver coin introduced by Constantine, and worth 1/24 of a
solidus. Originally it was 1/96 of a pound of silver, but his son, Constantius II reduced it to 1/144 of a pound of silver.

Bronze Coins

Sestertius
The orichalcum sestertius (plural: sestertii) was the largest bronze denomination in the early Roman Empire, and it continued, growing only gradually smaller until the reign of Postumus (usurper in the breakaway Gallic Empire, 259-258 AD) who minted the last sestertius. Because of their larger flan, the sestertii, particularly of the earlier empire, had the potential for exquisite reverses which many moneyers, particualrly under the Adoptive and Antonine dynasties, used to portray their finest works.
Dupondius
As
Semis
Image Not Yet Available Quadrans
The copper quadrans (plural: quadrantes) was worth a quarter of an as under Augustus. It was one of the smallest denominations in the Early Principate.
Follis
The bronze follis, originally silver washed, was a new denomination of Diocletian's monetary reforms. The follis, however, soon began to decline in diameter and weight. The follis then mingled into the AE category (below) as the size of bronze coins fluctuated radically. The example to the left is an earlier (therefore larger) version of the Follis.
Centenionalis
The bronze centenionalis were the attempts of Constans and Constantius II to reintroduce a large bronze coin, as the follis (above) had by then shrunk dramatically. The centionalis, however, did not last long and by the end of Theodosius the Great only smaller varieties of bronze coins were minted.

AEs
The bronze coinage of the later Roman Empire has too many varieties in diameter and weight. No record is known of the names of these denominations, or their worth. They are broadly categorised as AE1 (27mm or larger in diameter), AE2 (23 to 27mm), AE3 (17 to 23mm) and AE4 (less than 17mm). The two varieties pictured to the left are an AE3 of Valentinian I and an AE4 of Theodosius I.