When getting sized professionally, the most common approach is trying on various rings like these to find the right size.

Before buying a ring, it’s important to know your finger size. This may sound simple and straightforward, but that’s not always the case.

If you’re buying from a typical brick and mortar store, then this process should be easy. The sales associate can size you with what looks like a bunch of rings on a key chain, or you can try on different rings to find the right fit. Whether or not they have a ring in your size, though, is another thing. That’s actually one reason why people go online to shop, because the selection is much better with a wider variety of sizes available.

Another technique for determining ring size is to take a ring you wear regularly and have it sized. Basically, the ring is put on a mandrel (looks like a stick) and then the size is read from the middle of the ring (a distinction that is more important for wide men’s rings).

A ring mandrel looks like a stick with little notches like a ruler indicating size.

Ring sizes are unisex. Unlike clothes, there are no separate classifications for men’s sizes and women’s sizes. (Average women’s sizes range from 5 to 7, and common men’s sizes range from 8 to 11.) There is variation, however, between countries. In the U.S., sizes typically range from 4 to 16, whereas the U.K. will use letters. For example, a size 7 U.S. would be a size N 1/2 in the U.K. I often refer our international clients to Wikipedia for its very handy ring size conversion chart.

Rings fit differently too. Not all rings are made the same. Some are wide. Some are thin. Some are flat on the inside — referred to as standard fit. Some are rounded on the inside — referred to as comfort fit. Some are very rounded on the inside… “true” comfort fit versus “light” comfort fit. All of those things come into play when determining size. Consider what it’s like when trying to find the right pair of jeans or a pair of glasses. It can be tricky to get it just the way you want it, if you are sensitive to it.

This is why I always tell people: “If you’re not sure about the finger size, make sure you can return or exchange it.” This is particularly important when ordering online or through a catalog. (deBebians offers a 30-day return and exchange policy.)

Another factor that comes into play is the human body. Our bodies are always changing, and your finger size can and will fluctuate throughout the day. Factors that can increase your finger size include warm or hot weather and salty foods, and cold conditions will shrink your finger size.

Before I close, I just want to mention a few things to avoid. Don’t try to measure your ring size with a ruler, a piece of paper, a dime, a string, a piece of plastic, etc. It’s about as reliable as guessing your finger size. The two methods I mentioned above are the best. Any jewelry store will size you for free, and it’s best to go to a reputable jewelry store. A quick trip to a reputable jewelry store to get your size right the first time can save you a headache later.