How to Measure Ring Size

Getting engaged, or looking to buy a ring for a family member or special friend? One of the first things you will want to know is what size to buy, because when it comes to rings, size does matter. Too small and it will not fit, too big and it will slip off the finger.

Ring try on using ring sizer in home try on kit

First the facts: 

Ring sizes are measured in millimeters based on the inner circumference of the ring. Rings are sized on a standard scale so that a woman's size 6 is theoretically the same from jeweler to jeweler, but there can be small differences - in the same way that a size 4 dress at Ralph Lauren may not fit the same as a size 4 from another fashion design house.  

The US and Canada follow a numerical scale with half and quarter sizes; however, other countries may follow an alphabetical scale, which only uses whole sizes or includes a set circumference adjustments. All jewelers, however, use two different metrics of sizing: either measuring from the side edge of the ring or the center of the inside of the ring. The average ring size for women is between 5 and 7, but it is always best to get an exact ring measurement before spending a lot of money, as it is not always easy to re-size it after purchase.

There are several different ways to figure out the proper ring size, so you do not make a costly mistake. There are a variety of ring sizers and ring size charts you can print out to measure your ring size at home. When you print a ring size chart, make sure it is actual size, so choose "Scale 100" when selecting print options. The ring sizer measures the inside diameter of a ring; place it over the circles and see which one fits best.  

Jewelers use what is called a mandrel, which is a graduated metal wand with markers for size. The ring is slipped onto the mandrel and it rests on the correct size. If you do not want to go to a jeweler, you can buy your own mandrel to measure the correct size at home.

Another home method is to use a length of string to measure around your finger and compare it to the printed ring sizing guide, making sure the latter is printed to actual size. Wrap a piece of string around your ring finger and cut it at the point where the end overlaps, then line the string up with the ring size chart. 

If the ring size falls between two different sizes, you will want to go up a size, not down, because it is much easier to re-size a ring to make it smaller than the other way round. Your finger size may also change during the day, as a warm environment can cause fingers to swell. Also, you need to consider the style of ring you want. If you are leaning towards a ring with diamonds around the band, remember that the ring cannot be resized after purchase because it will stretch the metal holding the diamonds in place and cause them to fall out. 

How do you figure out her ring size if it is for a surprise proposal - and you don’t want her to know you are planning to pop that important question? 

You may have to opt for some covert operations. 

Find a family member, mother, sister, or a friend whom you trust to find your girlfriend’s ring size without her knowing. Borrowing one of her other rings, secretly, and getting it measured by a jeweler will give you the right answer. Another sneaky way is to take one of her rings and press it into a bar of soap to make a mold. A jeweler will be able to identify the correct size by looking at the marks it makes. Another way is to ask your secret helper to try on one of her rings without her knowing, so they can approximate its size according to theirs. 

Tips for finding ring size:

  • The ring should fit snugly, so that it goes on the finger easily, but is more difficult to take off, minimizing the risk of losing it. Take into account the size of the wearer’s knuckles. 
  • Finger sizes change during the year. Your ring will be tighter in the summer when it is hot, so make sure it is not too uncomfortable to bear during the heat. We recommend measuring your finger three to four different times because the size actually fluctuates depending on temperature: It can be smaller if you are or swollen if you are overheated.
  • If you are choosing a wide band, be aware that it will fit tighter. Most jewelers recommend you go up .25 or .50 with a wider band.

Your lab-grown diamond ring is an important investment, and it is vital to choose the right size. Some of the methods mentioned above, although convenient, may result in inaccuracies. 

At Stefano Navi, we offer an easy-to-use complimentary ring sizer to help you get the correct fit.