How Wide Is a Dime in Mm? Why This Tiny 17.91 Mm Coin Is Modern Science's Secret Ruler
By Maya Lin-Takahashi
The United States Mint enforces strict physical tolerances across all circulating coinage produced at its Philadelphia and Denver facilities. While people handle coins without considering manufacturing variances, the physical envelope of a dime requires micron-level repeatability to satisfy vending sensors, automated banking counters, and high-speed sorters.
The coin carries an outer diameter of 17.91 millimeters alongside a standard dime thickness in mm of 1.35 millimeters. Converted to imperial units, the diameter of a dime in inches is precisely 0.705 inches, with a thickness of roughly 0.053 inches. The coin's overall weight stands at 2.268 grams (0.080 ounces), equivalent to roughly 35 grains under traditional troy fractions.
These dimensions trace back to the Coinage Act of 1965, which transformed American circulating currency. Prior to 1965, the Roosevelt dime contained 90% silver and 10% copper. When surging precious metal values prompted widespread hoarding, federal authorities moved circulating dimes and quarters to a composite structure. The resulting modern cupronickel coin composition consists of an outer cladding made of 75% copper and 25% nickel, bonded permanently to an inner core of pure copper. Overall, copper accounts for 91.67% of the coin's total weight, with nickel making up the remaining 8.33%.
This layered metallurgical design matches the electrical conductivity and magnetic signature of traditional silver coins, preventing widespread obsolescence in coin-operated equipment while holding absolute dimensional stability across billions of strikes.
Maya is a hardware enthusiast who tests and reviews smart home devices, smartphones, wearables, and audio gear. She focuses on practical consumer value and build quality.
