A few millimeters can make a big difference.

Engagement Ring
Credit: Tetra Images - Jamie Grill/Getty Images

When it comes to weddings, many trends will come and go. From engagement photo shoots to bridal registries, each generation of newlyweds redefines the expectations associated with wedding parties. A modern marriage doesn't have to follow the same rules as traditional weddings of years past—from blush bridal gowns to honeymoon funds, today's brides are redefining the world of weddings. They're trading sleek updos for more relaxed, flowing hairstyles; they're swapping traditional china sets for modern kitchen must-haves. But despite countless evolving traditions, one symbol has remained sacred: The diamond ring.

Wedding rings have been worn since antiquity, but diamond engagement rings first rose to prominence in the fifteenth century among European royalty and the higher classes. The circular shape of the ring symbolizes eternal commitment—it has no end point—and diamonds themselves represent pure love. With these symbolic values, a diamond ring is the perfect way to start a union; today, it's become a constant feature in most engagements. In fact, according to Diamond Council of America, 84% of today's US brides receive a diamond engagement ring.

While we wouldn't trade this tradition for anything, there's one problem that most hopeful suitors run into: Rings come in countless sizes. Buying a ring as a gift can be tricky if you don't know the recipient's ring size—while you can make an educated guess, it'd be disappointing to discover that the ring doesn't fit (especially if you're investing in a sparkler with a high price tag). We'd never try to guess at a friend's shoe size, so how are men supposed to guess the circumference of a significant other's finger down to the millimeter? Luckily, it's possible to have rings resized—but ideally, you'll get it right on the first try.

While you may automatically associate rings with weddings, there are a plethora of other cases and situations when you'll want to know a ring size. For example, if you are ordering a class ring for your college graduation, or if you're simply ordering jewelry online, you'll need to order a ring that's tailored to your finger size.

Unless you're going to the jeweler to make a big purchase, you probably won't have access to professional ring sizing equipment. But that shouldn't stop you from shopping for rings! We have a quick and easy way to size your fingers at home. Size your finger and write down the size for when you may need it. And who knows—soon enough, a special someone may need access to this information, too.

General Ring Sizing Guide

A well-fitting ring will sit comfortably at the base of your finger. It will slide off easily, but it won't be so loose to risk falling off on its own. It also won't be so tight to cut off circulation or change the color of your skin (it's worth noting that rings containing nickel or copper can cause skin discoloration, leaving the area of your skin a greenish-blue).

Ring sizes are measured in millimeters, with each half-size separated by 0.4 millimeters and each full size separated by .8 millimeters. This means that a fraction of a millimeter can completely change your ring size, so you'll want to ensure your measurements are as accurate as possible. Once you've measured your finger using one of the methods listed below, you can refer to this conversion chart to find your perfect ring size.

Ring Sizing Chart
Credit: Alexey Bezrodny/Getty Images

How To Measure Ring Size Using String or Floss

If you don't have a ring handy, this easy ring sizing method will help you get an accurate measurement of your finger size without any professional equipment.

The Supplies

All you'll need to measure your finger at home is a few simple supplies:

  • A piece of string or floss
  • A pen
  • A ruler with millimeter measurements

How To Measure Ring Size

  1. Cut a piece of string or floss that's at least 4 inches long.
  2. Wrap the string/floss completely around the base of the desired finger (the spot where you'll wear the ring), marking where the strings overlap with a pen. Do the same for the knuckle of the finger.
  3. Lay the string flat and use the ruler to measure the length in millimeters. Average the length between the finger base and the knuckle.
  4. Use the provided chart to translate the millimeter measurement into your ring size.

How To Measure Ring Size Using Another Ring

If you already have a ring that fits you well but you're unsure of its size, you can use this ring to determine your measurements.

The Supplies

  • A ring that fits the desired finger
  • A ruler with millimeter measurements

How To Measure Ring Size

  1. Measure the diameter of the inside of the ring.
  2. Use the provided chart to translate the millimeter measurement into your ring size.

Important Factors to Remember When Sizing for a Ring at Home

Each Finger is Different

Each of your fingers will be slightly different sizes. If you plan on wearing the ring on your left ring finger, be sure this is the finger that you size. If you want to wear a trendy ring on your middle finger or pinky, size these fingers. Another factor to consider: The fingers on your dominant hand may be slightly larger than the fingers on your non-dominant hand.

Temperature Matters

Have you ever noticed your fingers swelling when it's hot out? This is because temperature can actually impact the size of your fingers. Fingers tend to swell up in the heat and shrink slightly in the cold. Since you'll want to be able to wear your ring year-round, try to measure your finger in hot weather when it's at its largest. This way, you won't get a ring that won't fit over your finger in the summertime.

Size More Than Once

As stated above, your finger size can fluctuate and change based on the weather, the season, or other outside factors. If you want to ensure the accuracy of your measurement, size your finger a few different times at multiple points throughout the week, month, or year. This will help you gauge the average size of your finger over time and calculate a more accurate measurement.

Measure Various Parts of your Finger

Keep in mind that the part of your finger that you're sizing—the ridge where your finger meets the rest of your hand—is slightly tapered in. Your knuckle may be wider than the portion of your finger where you'll actually wear the ring. A ring that fits well will slide over your knuckle to rest comfortably and snugly on your finger, and will not be too loose to slide back over your knuckle easily. To ensure the ring will fit over your knuckle, measure the size of your knuckle as well as the spot where you'll wear the ring.

When in Doubt, Size Up

Professionals will typically recommend that, if you're between two sizes or deciding which size to order, you opt for the larger size. A ring that's a little loose is ultimately more wearable than a ring that won't fit onto your finger. In the case of adjustments, it's also much easier to resize the ring to make it smaller than to expand it to make it larger (which would require sourcing the same metal or material used to make the ring).

WATCH: 16 Unique Engagement Rings That'll Make You Say 'I Do'

How To Get Someone Else's Ring Size

If you're a hopeful suitor looking to propose or merely a friend or family member who wants to gift a cute ring, you'll need to find the recipient's ring size. With friends, it's easier to sneak the question in without causing suspicion, but when it comes to engagements, your partner is more likely to read into the question. If you want to maintain the shock factor of the proposal, downright asking for a ring size can be tricky. Here are a few of our strategies for finding out someone else's ring size.

The Cardinal Rule: Stay Honest (and Subtle)

You shouldn't be jumping through hoops to secretly acquire your partner's ring size. (Read: Please do not attempt to secretly measure their fingers in their sleep.) There are many other ways to go about this task, but subtlety is key.

That being said, it's completely acceptable to ask your partner downright for her ring size—just be vague as to the purpose of this request. Chances are that if you're in a serious, committed relationship, she already suspects the proposal is coming soon anyways. If she catches on to the purpose of the question, the worst it can do is start an open, honest dialogue about your future together. Ultimately, knowing that you're buying a ring doesn't have to ruin the surprise and fun of when, where, and how you'll propose.

But, if you want to stay sneaky, here are a few ways you can find your partner's ring size on the down-low.

  1. Take her ring shopping. As a fun weekend activity, take your partner to a jewelry store and have her try on some rings. This will not only allow you to learn her ring size, but it will also help you get a feel for the style and cut of the rings she likes. It's important to get a ring that suits her tastes—she'll likely be wearing it for the rest of her life, after all!
  2. Phone a friend. Ask your partner's mom, sister, or friends to help you get your partner's ring size. Chances are her girlfriends will be able to execute this task without raising much suspicion. After all, Mama always knows best.
  3. Phone the jeweler. If your partner has shopped at a local jewelry store before, call the store to see if they have her ring size on file. If you have shared accounts online, you can also check her purchase history to see if she's bought any rings in her size.
  4. Borrow one of her rings. If your partner already wears rings frequently, borrow one of the rings from her jewelry box and use the above tactic to measure it at home (or take it to the jeweler's). If you don't want your partner to notice her ring's gone missing, you can also quickly trace the inside of the ring onto a piece of paper and measure the diameter later. Just be sure to keep in mind which finger she wears this ring on, because that can change the measurement.
  5. Think ahead. Ask your partner her ring size early on and write it down to save for later. Not only can you now get her other rings as gifts, but when the big day comes, you'll be prepared.