For girls or very young women: Choose pearls no larger than 7.0mm.
For petite women who are very slim or women who like dainty things: Choose pearls up to 7.0mm or 7.5mm.
For most women: Bigger is better when it comes to pearls, although not all women like pearls over 12.0mm in size. So when choosing pearl size, go for the largest pearl size in your chosen price range without compromising quality.
Freshwater Pearls: The most popular sizes for pearl necklaces are between 6mm and 9mm. (Classic white pearl necklaces are often 7.0-8.0mm pearls. Mature women usually prefer 8.0-9.0mm pearls.)
Akoya Pearls: The most popular sizes for pearl necklaces are between 6.0mm and 8.5mm. (Classic white pearl necklaces are often either 6.5-7.0mm or 7.0-7.5mm pearls.)
Tahitian Pearls: The most poplular sizes for round pearl necklaces are between 8.0mm and 12.0mm. Baroque Tahitian pearls may be larger.
South Sea Pearls: The most popular sizes for pearl necklaces are between 9.0mm and 14.0mm.
What do the millimetre sizes mean? 6mm is just under a quarter of an inch. That's about the size of the diameter of the eraser on the bottom of a pencil. 13mm is about the size of an old fashioned marble. That's about half an inch.
Does .5mm difference in size really look any bigger? The price difference seems a lot. Yes, every half a millimetre of size increase does look bigger. This is because the pearls are spherical, so even a small increase in linear size is quite a big increase in volume. The oyster secretes many layers over a long time to make the pearl even fractionally bigger, so time and costs are a lot more.