How To Size a Marble

The size of a marble is measured by its diameter in inches. Marble manufacturers utilized a sieve system of measuring. Using a device that measured marbles in 1/16” increments, the smallest opening that the marble would fall through was the size. Because of this method, the marbles classified as one size by a manufacturer could in fact vary by 3/64”.


You can duplicate this process by using a Circle Template, available at Staples and other office supply stores. The smallest hole that the marble will fall through is the diameter. Alternatively, you can use a caliper to measure diameter. Only use plastic calipers so that you don't scratch the marble.


Marbles under 1-1/4" are generally sized in 1/16" increments, because this is the size increment that manufacturers used. In practice, any marble under 2-1/2" is usually sized in 1/16" increments. Over 2-1/2" it is usually 1/8" increments.


Back in the late 1800s and early 1900s, it was technically impossible to produce a handmade glass marble in sizes much greater than about 2-3/4” in diameter. The marble would sag and deform during the annealing process because of its weight. However, different types of marbles are more common in some sizes than others. Machine-made marbles are usually 1/2” to 3/4”. This is because marble tournament regulations set the size of the shooters to be between 5/8” and 3/4” and the size of the target marbles to be 5/8”. Again, the relative rarity of different sizes varies greatly from one type of marble to the next.