Pearls can range anywhere from under 1mm to giants of 20mm or more. As you can see, pearls are usually measured in millimeters, and are measured through the diameter. For most round pearls, the most popular size resides somewhere between 7mm and 7.5mm. Of course,size isn't the only factor to be considered when buying pearls. While you could pay off a small home if you were to sell a 20mm pearl, there are a number of other elements that make for a valuable pearl. For example, a clean, round 7mm pearl with good luster is more valuable than a baroque pearl that is dull, even though it may be 9mm.

However, since there are so many important factors to consider when you want to buy pearls, size is normally a good jumping off point for your decision making.

On a petite woman, a strand of pearls between 5 and 6mm is not only more affordable (as they are more available), but it usually looks much nicer when strung in a single on a petite frame, or on a taller woman in double, and even triple strands.

 
The size of 6 to 7mm is a nice size to look luxurious but still remain affordable. Strands in this size look very beautiful, and are considered to be a terrific value. These are the perfect pearls for the young professional, or for casual wear. Generally, this size offers the largest selection, so you should be able to locate some pearls of fine quality, still within your price range.

For something truly elegant, for evenings and fancy occasions, the favorite size tends to be 7 to 8mm. Necklaces in this size simply look gorgeous. At 40% larger than strands of 5 to 6 mm, they show their appealing qualities just that much more, without flaunting. Social outings and evenings at the theatre are perfectly accessorized in this size strand of pearls. However, buying a strand in this size can be quite the challenge. While pearls of smaller size are more likely to be of consistent quality all the way around the strand, it is more challenging for jewelers to come up with the pearls they need for a consistent 7 to 8mm strand. Therefore, you should be careful to have a look at what each pearl looks like in a strand of this size, to ensure consistent beauty and quality.

If you really have a soft spot for big pearls, keep in mind that anything above 8mm is considered to be high end and may set you back a pretty penny. This is because these larger pearls are more difficult to find and jewelers can not always guarantee their availability. Larger pearls are naturally not for everyday wear. They should be for special occasions, or if you really need to add something to a power business suit, or a lower cut dress.

Many factors determine the size of a pearl as it is being formed. The most important factor is the type of pearl itself, as well as the location in which it was formed.

A saltwater pearl, for example, the Akoya, will usually range from 5mm to 8.5mm. Conversely, a Tahitian pearl can grow up to 13mm; though the largest one was 25mm in diameter.

Pearls that are larger than 9mm are almost always black Tahitians, white South Sea pearls, or even large freshwater pearls. When shopping for pearls, begin with the size and then you'll be ready to face color, luster, surface, and all of the other aspects involved in pearl grading.