What is the diameter of a quarter in mm? Coins come in all shapes and sizes, with diameters ranging from small to large. If you’ve ever wondered about the size of a quarter, one of the most common coins, you’ve come to the right place.

If you’re short on time, here’s a quick answer: the diameter of a quarter is 24.26 mm.

In this comprehensive article, we will explore everything you need to know about measuring the diameter of a quarter, from the history of the coin’s size to how it compares to other coins in circulation.

The Origins of the Quarter Coin

Introduction of the Quarter in 1796

The quarter coin was first introduced in the United States in 1796, as part of the Mint Act signed by President George Washington. The quarter, along with other coins such as the half dollar and silver dollar, were authorized due to a need for new circulating coinage in the young nation.

The original quarter design featured a depiction of Liberty on the front and an eagle on the back. The very first quarters were minted in silver and had a diameter of approximately 27mm and a weight of 6.74 grams. This first design was attributed to noted early American engraver Robert Scot.

Changes to the Quarter Over Time

Over the two centuries since its introduction, the quarter has undergone some key design changes and variations:

  • In 1838, the eagle on the back of the quarter was replaced with a depiction of a seated Liberty.
  • The “Seated Liberty” quarter design lasted for over 50 years until 1892, when the iconic Standing Liberty quarter was first released into circulation. This stunning design is a favorite of collectors today.
  • In 1932, the Washington Quarter entered circulation, bearing the first United States coin portrait of an actual historical figure – the first president, George Washington. This enduring design remains on the quarter to this day.
  • Starting in 1999, the 50 State Quarters program saw a unique commemorative quarter design released every 10 weeks to honor each U.S. state. This program ran for over a decade and is credited with renewing a strong interest in coin collecting.

Overall the design variations and programs, the quarter has maintained the same diameter, mass, and composition (a copper-nickel mix) since 1965. Today it remains an extremely widely circulated coin, with approximately 1.6 billion quarters produced every year by the U.S. Mint.

Measuring a Quarter

Using a Ruler or Calipers

To precisely measure the diameter of a United States quarter dollar coin, a ruler or caliper tool can be used. Most quarters have a diameter right around 24.26 mm, though there is some variation allowed in the minting process.

Using a standard ruler marked with millimeters or a dial calipers adjustable to metric units will allow an accurate reading. Care must be taken to properly align the coin in the calipers or place it evenly along the ruler markings to get the true diameter. Some specialty rulers meant specifically for coin collecting have pre-marked notches for common coin sizes that make this easier.

When using a ruler, the quarter should be placed vertically between the markings, with the flat sides pressed gently against the edges of the ruler. The measurement should be taken from the outermost edges of the reeded pattern on the sides of the coin.

Taking several measurements and averaging them helps account for tiny blemishes or uneven wear on the coin’s edges. Digital calipers that can display fractional millimeters may provide the most precision.

Converting Inches to Millimeters

If a ruler or device marked only in inches or fractions of an inch is used, converting the measurement to millimeters is straightforward. One inch equals exactly 25.4 millimeters. Most U.S. quarters have a stated diameter of 0.955 inches.

To convert, the fraction of an inch must first be converted to its decimal equivalent by dividing the numerator by the denominator. 0.955 inches multiplied by 25.4 mm per inch gives 24.26 mm.

Some older quarters varied slightly in size from the modern measurements. Up until 1965, quarters were minted from 90% silver and had a diameter of 24.26 mm. From 1965 onward, new copper-nickel-clad quarters were introduced that were slightly smaller at 24.13 mm across.

So a quarter’s precise diameter depends partly on its mint year and metal composition. But nearly all will be around 24-24.3 mm across.

The Quarter’s Official Diameter

Diameter Defined

The diameter of a circle is the length of a straight line drawn between two points on the circle that passes through its center. Simply put, it is the width of a circle measured through its midpoint. For a common coin like a quarter, knowing its diameter gives us a sense of its overall size and dimensions.

The Quarter’s Diameter in Millimeters

According to the United States Mint, which produces billions of coin currency each year, the official diameter of a quarter is 24.26 mm. This measurement has been carefully defined to allow the quarter to work properly in vending machines, toll booths, laundromats, and any other application where coin currency is used.

To give some perspective on how small 24.26 mm is, it is slightly smaller than the diameter of a golf ball, which measures 42.67 mm. So a quarter is quite tiny compared to a golf ball, even though we don’t usually think of quarters as being small coins when using them.

The quarter underwent a redesign in 1932, transitioning to a smaller diameter of 24.26 mm from the previous diameter of 27 mm used in earlier versions of the coin. This change in size brought the quarter’s diameter in line with that of the nickel (21.21 mm), dime (17.91 mm), and half-dollar (30.61 mm) to streamline manufacturing and acceptance.

So the next time you have a quarter, know that it is precisely 24.26 mm in diameter. This small size and thickness allow it to easily fit into vending machines, parking meters, coin rolls, and pockets as it goes about its circulation carrying out approximately 25 cents worth of commerce with every exchange.

How the Quarter Compares To Other Coins

Diameters of Pennies, Nickels, and Dimes

When comparing the diameter of a quarter to other popular US coins like pennies, nickels, and dimes, there are some clear size differences. According to the United States Mint, the specifications are:

  • Penny – 0.75 inches (19.05 mm)
  • Nickel – 0.835 inches (21.21 mm)
  • Dime – 0.705 inches (17.91 mm)
  • Quarter – 0.955 inches (24.26 mm)

As you can see, the quarter is the largest of the four coins in diameter. It beats out the penny by 0.205 inches (5.21 mm), the nickel by 0.12 inches (3.05 mm), and the dime by 0.25 inches (6.35 mm). So if you were stacking these coins in order of increasing diameter, it would go penny, dime, nickel, quarter.

Visual Comparisons

Another helpful way to compare the size of a quarter to other coins is through visuals. Placing the quarter next to the smaller penny, nickel, and dime makes the size difference very apparent.

Penny vs. Quarter The penny looks tiny compared to the wide quarter. You could fit almost 3 pennies inside the diameter of one quarter!
Nickel vs. Quarter The nickel is closer in size but still noticeably smaller than the quarter. About 4 nickels lined up would equal the diameter of one quarter.
Dime vs. Quarter Stacked next to the quarter, the dime looks miniature in comparison. You could line up almost 2 and a half dimes to reach the full diameter of a single quarter.

So visually, it’s quite obvious that the quarter dominates over the smaller penny, nickel, and dime in terms of sheer diameter size. The quarter maintains its top spot as the largest coin of the four most common US coin denominations.

For further size comparisons and visuals of coins, check out the useful graphic at US Mint Coin Specifications.

Numismatic Context

Collector Interest in the Quarter

The quarter is one of the most popular coins collected by numismatists and hobbyists. According to data from the American Numismatic Association, over 200,000 people collect Washington quarters minted before 1965.

The unique designs and low production of early quarters make them highly desirable for collectors looking to complete a set.

Some key reasons quarters catch collector interest include:

  • Early quarters (1932-1964) have a silver composition that makes them intrinsically more valuable
  • Proof and silverproof quarters are specially struck for collectors with mirrored surfaces and extra polish
  • Errors like off-center strikes and double-die coins appeal to specialists seeking dramatic oddities
  • Low mintage issues like the 1932-D can command over $1,000 in top condition due to scarcity

Modern issues also find an audience, with many Americans collecting one or more of the America the Beautiful series showing national parks and sites or the 50 State series with unique reverse designs based on each state. The huge variety gives hobbyists an achievable yet engaging lifetime challenge.

Errors and Variations

Production glitches and die anomalies have produced some remarkable Washington quarters over the years. Major error types include:

Off-center strikes – The blank is fed incorrectly through the press causing a dramatic displacement of the design. Broadstrikes – A coin is struck without the collar to form the rim and outline the design.
Double die obverses – Doubling of design elements from a die imprinting the blank twice. Die breaks – Breaks/cracks in the die face cause raised irregular lines across coins.

These types of errors are scarce but highly sought-after by specialists. For example, a 2000-P New Hampshire quarter with a dramatic off-center strike sold for over $1,200 at a public auction in 2022.

There are also many minor design variations discovered through close study of the Washington quarter series. These include smaller doubled die details, repunched mint marks, clash marks from die damage, die chips/cracks, and many other anomalies.

While less obvious to casual collectors, they give interested hobbyists and numismatists an intriguing aspect to study for this very common coin.

What Is The Diameter Of A Quarter In MM – Conclusion

As we have seen, the quarter has an official diameter of 24.26 mm, originating from its introduction in the late 18th century.

While the quarter’s diameter has stayed largely consistent, it remains unique compared to other circulating US coins.

Understanding the quarter’s size gives helpful context for everyday use, collecting, and more. Equipped with this knowledge, you can confidently handle quarters of all types.

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