How the denarius's silver content changed, why a different coin later displaced it, and what the surviving fineness estimates can—and cannot—tell us about Roman money.
Under Augustus, the denarius was about 3.9 grams and nearly pure silver. By the 260s AD, the denarius had largely given way to the antoninianus; NGC's fineness series puts some antoniniani of Gallienus at 5% silver or less, with a few around 2.5%. Those figures describe estimates for surviving issues, not every coin or a continuous fall in the same denomination.
A coin built for a war
Rome introduced the denarius around 211 BC, during the Second Punic War. Britannica gives its early weight as about 4.57 grams. It became a principal Roman silver denomination and remained in use for centuries.
Under Augustus, the denarius standard settled at about 3.9 grams and roughly 98% fine. This was the imperial coin before successive changes in weight and fineness.
Nero makes the first cut
The first big reduction came from Nero around 64 AD. He lowered the weight by roughly 12.5%, to about 3.3 or 3.4 grams, and dropped the fineness from about 98% to roughly 93%. NGC's series on the decline of Roman silver coinage gives those figures, and they matter less for their size than for what they started. Once an emperor had shown that the silver content could be quietly reduced, every stressed treasury had the same option on the table.
It is worth knowing that emperors did try to go back. Domitian restored the old purity around 84 AD, then reversed himself within a year or so and accepted the lower standard again. Good intentions did not survive contact with the cost of the army.
The slide, century by century
Fineness percentages for ancient coins are estimates based on surviving specimens. The imperial figures through Gallienus follow NGC's published series; the table also draws on Britannica for the Republic-era weight and Carson for Aurelian's reform. Figures are approximate, not guarantees for every coin. From Caracalla onward, the percentages refer to the antoninianus, which largely replaced the denarius.
| Period | Reported fineness or weight | Notes |
|---|---|---|
| c. 211 BC (Republic) | about 4.57 g | Britannica gives this early weight; the cited page does not establish a fineness percentage |
| Augustus, 27 BC–64 AD | ~98% or higher, ~3.9 g | The classic denarius |
| Nero, c. 64 AD | ~93%, ~3.3–3.4 g | First great reduction |
| Vespasian, 69–79 | ~89%, sometimes ~80% | Post civil-war finances |
| Trajan, from 107 | ~89–90% | Slow drift continues |
| Antoninus Pius, by 148 | ~83–84% | Falls during a famously peaceful reign |
| Commodus, by the 190s | ~71% | Second century ends well below where it started |
| Septimius Severus, 193–211 | ~57% | NGC's published estimate |
| Gordian III, 242–244 | ~37% (Rome), ~43% (Antioch) | Mints differed from each other |
| Valerian, by 260 | as low as ~15% | Empire under simultaneous invasion and civil war |
| Gallienus, by 268 | ~5% or less, some ~2.5% | Effectively bronze coins wearing a silver face |
| Aurelian's reform, 274 | reformed antoninianus; about 5% silver in NGC's account | A new standard, not a return to the earlier denarius |
Why emperors did it
Military expenditure was one important pressure on imperial finances, but it was not the only cause of each change in coinage. Under Septimius Severus, the denarius's fineness fell to around half in NGC's series. Reducing silver content allowed a given amount of metal to support more coins; the fiscal effects and public response varied by period.
Caracalla introduced the antoninianus in 214/215, apparently tariffed at two denarii, but it weighed only about one and a half times as much as a denarius. On that basis it contained less silver than two denarii; this comparison does not by itself show how people valued or used it.
The silver wash
Late antoniniani could retain a bright silver-coloured surface despite having little silver in the alloy. The visible finish is not literal paint, and a coin's appearance alone cannot establish its composition; the low fineness estimates come from analysis of surviving issues.
What it did to the people holding the coins
Debasement formed part of a broader third-century crisis that also included civil wars, disease, and invasions; the coinage alone cannot explain it. In 301, Diocletian issued an Edict on Maximum Prices listing limits for goods and services, including wages. Its preface blames greed and profiteering. That is evidence of the government's stated rationale, not a neutral account of the causes of inflation or proof of how every household experienced it.
The edict's reach and effects are debated, so describing it simply as a failure overstates what the cited evidence establishes. Aurelian's later reform altered the coinage standard; it was not a return to the earlier denarius. By the third century the denarius had largely disappeared as a silver coin, though its name continued as a unit of account.
Sources & References
- Encyclopaedia Britannica: denarius: introduction and Republican weight
- NGC Ancients: The Decline of Roman Silver Coinage, Part I (11 September 2018): fineness series from Augustus to Gallienus
- British Museum object record 1946,1004.770: denarius of Septimius Severus
- British Museum object record R.15321: denarius of Septimius Severus
- Online Coins of the Roman Empire: RIC IV Septimius Severus 29A
- R.A.G. Carson, "The Reform of Aurelian", Revue numismatique (1965)
- A. Wassink, "Inflation and Financial Policy under the Roman Empire", Historia 40 (1991)
- Overview of Diocletian's Edict on Maximum Prices (301) and the Aphrodisias fragments — a secondary summary, not a substitute for the inscriptions or specialist studies.
- Image: Caracalla antoninianus, Wikimedia Commons, CC0
- Image: Gallienus antoninianus, Wikimedia Commons, CC0
Fineness percentages are scholarly estimates for the period rather than guarantees for every coin, and where published series disagree the table shows the range. Reviewed against these records on 7 September 2026. If a date, figure, or interpretation needs correction, please contact hello@cointoss.uk.