United States circulating coinage is manufactured by the United States Mint under strict legal dimensional tolerances. Whether you are identifying an unknown coin, verifying coin slots, checking a vending machine coin mechanism, or using a coin as a makeshift physical ruler, having exact official measurements in both millimeters and inches is indispensable.
Official United States Mint Coin Specifications Table
The table below provides official specifications published by the United States Mint for currently circulating denominations:
| Coin Denomination | Diameter (mm) | Diameter (in) | Thickness (mm) | Weight (grams) | Edge Detail | Official Composition |
|---|---|---|---|---|---|---|
| Penny (1 Cent) | 19.05 mm | 0.750 in | 1.52 mm | 2.500 g | Plain | 97.5% Zinc, 2.5% Copper |
| Nickel (5 Cents) | 21.21 mm | 0.835 in | 1.95 mm | 5.000 g | Plain | 75% Copper, 25% Nickel |
| Dime (10 Cents) | 17.91 mm | 0.705 in | 1.35 mm | 2.268 g | 118 reeds | Cupronickel (91.67% Cu, 8.33% Ni) |
| Quarter Dollar (25 Cents) | 24.26 mm | 0.955 in | 1.75 mm | 5.670 g | 119 reeds | Cupronickel (91.67% Cu, 8.33% Ni) |
| Half Dollar (50 Cents) | 30.61 mm | 1.205 in | 2.15 mm | 11.340 g | 150 reeds | Cupronickel (91.67% Cu, 8.33% Ni) |
| Native American / Golden Dollar ($1) | 26.49 mm | 1.043 in | 2.00 mm | 8.100 g | Lettered edge | Manganese Brass (88.5% Cu, 6% Zn, 3.5% Mn, 2% Ni) |
Detailed Denomination Analysis
1. The Lincoln Penny (1 Cent)
The US cent has a standardized outer diameter of 19.05 mm (exactly 0.750 inches, or 3/4 of an inch). Since mid-1982, pennies are composed of a zinc core (97.5%) plated with a thin copper jacket (2.5%), weighing exactly 2.500 grams with a thickness of 1.52 mm. If measuring pre-1982 bronze pennies, note that their composition was 95% copper and 5% zinc, weighing 3.110 grams. Their outer diameter, however, remained unchanged at 19.05 mm.
2. The Jefferson Nickel (5 Cents)
The US five-cent coin has a diameter of 21.21 mm (0.835 inches), a thickness of 1.95 mm, and weighs exactly 5.000 grams. Because it weighs exactly five grams, two fresh nickels can serve as a dependable 10-gram calibration weight for digital pocket scales.
3. The Roosevelt Dime (10 Cents)
The dime is the smallest and thinnest circulating coin in the United States, measuring 17.91 mm (0.705 inches) across with a thickness of only 1.35 mm and a weight of 2.268 grams. Its reeded circumference features 118 distinct vertical ridges.
4. The Washington Quarter Dollar (25 Cents)
Measuring 24.26 mm (0.955 inches) with a thickness of 1.75 mm and a weight of 5.670 grams, the quarter is the most widely circulated denomination in American commercial vending. Its outer edge has 119 reeds.
5. The Kennedy Half Dollar (50 Cents)
The half dollar is the largest circulating clad coin produced by the US Mint, with a diameter of 30.61 mm (1.205 inches), a thickness of 2.15 mm, and a substantial mass of 11.340 grams. It features 150 edge reeds.
6. The Golden Dollar ($1)
The modern dollar coin (Sacagawea, Presidential, and Native American series) has a diameter of 26.49 mm (1.043 inches), a thickness of 2.00 mm, and a weight of 8.100 grams. For older historical dollar coins, such as the Susan B. Anthony dollar (1979–1999) which featured a reeded edge and copper-nickel clad composition, or earlier silver Morgan/Peace dollars (38.1 mm diameter), check before relying on this as older collectible issues carry distinct physical dimensions.
Using US Coins for Real-World Size Estimation
Knowing coin sizes helps you gauge unfamiliar objects on the fly:
- Need a 3/4 inch gauge? Lay down a penny (19.05 mm is exactly 0.750 inches).
- Need an approximate 1 inch reference? A quarter (24.26 mm / 0.955 in) is slightly under an inch (off by just 1.14 mm), while a Golden Dollar (26.49 mm / 1.043 in) is slightly over an inch.
- Need a 5-gram balance weight? A US nickel weighs exactly 5.000 grams.
Frequently Asked Questions
Why is a US 10-cent dime smaller than a 5-cent nickel?
Historically, US dimes were minted from 90% silver, where physical intrinsic metal value equaled face value. The nickel contained cheaper base metals (copper-nickel alloy) and required larger physical volume to maintain distinct tactile weight.
Can I use a US quarter to calibrate an online ruler?
While a quarter measures exactly 24.26 mm, we recommend calibrating with an ISO ID-1 credit card (85.60 mm) instead. A credit card is more than 3.5 times wider, which substantially reduces human eye alignment error.
Do older pennies have different weight or thickness?
Yes. Pre-1982 pennies were 95% copper and weighed 3.11 grams. Modern zinc-core pennies weigh 2.500 grams. Their official diameter remains 19.05 mm across both eras.
Measure your coins right now!
Calibrate your screen and measure your pocket change down to the millimeter:
Source: United States Mint Official Coin Specifications.