How this instrument works
The word dime traces to the Latin decimus, meaning tenth, by way of the French disme. The Coinage Act of 1792 used that original spelling, establishing the 'disme' as one-tenth of a dollar in America's brand-new decimal currency — a coinage system built entirely around units of ten rather than the fractional shillings and pence Europe still used. Federal law still states it plainly today: 31 U.S. Code §5101 defines a dime as a tenth of a dollar.
Today's dime is a physically smaller coin than either the penny or the nickel — 17.91 mm across, thinner and lighter than both — even though it is worth more than either, a mismatch that surprises people the first time they line the three coins up side by side. It is also the only US coin with a reeded edge originally cut for a reason that no longer applies: preventing silver shavings before 1965, when dimes still contained 90 percent silver.
The reeded edge survived a major redesign. The Coinage Act of 1965 stripped silver from dimes and quarters entirely, replacing it with a copper-nickel clad sandwich — the same 75% copper, 25% nickel alloy already used on the five-cent piece — bonded around a pure copper core, in response to a coin shortage caused by silver hoarding as bullion prices rose past the coins' face value.
Since 1946 the dime has carried the portrait of Franklin D. Roosevelt, chosen because Roosevelt helped found the March of Dimes to fight the polio he himself had lived with since 1921 — the charity's name came directly from its practice of asking ordinary Americans to mail in a dime each, which made the ten-cent coin the natural choice once officials began planning a memorial coin after his death in 1945.
- Enter a count into the Dimes field — 25 is preloaded to show the ×0.1 factor at work.
- US dollars updates instantly, always your dime count divided by exactly 10.
- To reverse it, multiply a dollar figure by 10 to see how many dimes it represents.
- A standard bank coin roll holds 50 dimes; enter 50 to check that it equals exactly $5.00.
Worked example — counting 25 dimes from a coin jar
Someone rolling loose change from a coin jar sorts out 25 dimes to wrap for the bank. Entering 25 into Dimes returns 2.5 in US dollars — the exact figure to write on the coin wrapper before sealing it, well short of the 50-dime, $5.00 roll a bank teller would expect, so another 25 dimes need to be added to fill the roll completely.
The same ×0.1 factor scales to any count: 7.5 dimes, an unusual but valid fractional entry for calculating partial rolls, converts to $0.75, and a single dime converts to exactly $0.10. Multiply 2.5 back by 10 and the count returns to 25 dimes precisely, confirming both directions of the conversion agree exactly.
Questions
How many dimes make a dollar?
Exactly 10. A dime is legally defined as one-tenth of a dollar under 31 U.S. Code §5101, so ten of them always sum to $1.00 with no rounding involved — the relationship is fixed by statute, the same way it has been since the Coinage Act of 1792 first defined the disme.
Why is the dime smaller than the penny and nickel despite being worth more?
Coin size in the US was never set to track face value — it originally tracked the value of the precious metal each coin contained. When dimes were struck in silver, a coin worth ten cents needed far less silver by weight than a nickel needed in base metal, so the dime stayed small even after 1965, when both coins switched to the same copper-nickel clad alloy.
Why does the dime have a reeded edge?
It is a holdover from the coin's silver era. Reeding — the fine ridges around the edge — made it easy to spot someone shaving slivers of precious metal off the rim of a 90%-silver dime before 1965. The dime kept its reeded edge after switching to copper-nickel clad in 1965, even though the coin no longer contains any metal worth shaving.
Why is Franklin D. Roosevelt on the dime?
Because of his direct connection to the March of Dimes, the charity he helped found to fight polio, a disease he had lived with since 1921. The organization got its name from asking ordinary citizens to mail in a dime each to support treatment and research, so the ten-cent coin was the natural choice for his memorial portrait when the Mint redesigned the dime in 1946, the year after his death.
What happened to silver dimes after 1965?
The Coinage Act of 1965 replaced 90%-silver dimes and quarters with a copper-nickel clad sandwich, in response to a national coin shortage caused by people pulling silver coins out of circulation as bullion prices rose above face value. Pre-1965 silver dimes are still legal tender today but circulate almost exclusively as collectibles, since their metal value now runs well above ten cents.
How many dimes are in a standard bank roll?
50 dimes, worth exactly $5.00 — the standard wrapper size US banks and the Federal Reserve use for dimes, distinct from the 40-coin roll used for nickels and quarters, though it happens to match the 50-coin roll used for pennies.