How to Determine the Perfect Engagement Ring Size

Before your significant other puts a ring on it, here's how to accurately gauge your perfect size

Updated 11/03/17
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Jeffrey Coolidge

Your engagement ring will be a constant (sparkly) symbol of your marriage, long after your wedding day has passed. That's why it's of the utmost importance that you have an accurate measure of your ring size before your partner pops the question. Nothing's more disheartening than losing such a precious gem to the depths of your kitchen sink's drain, or, on the other end of the spectrum, having it cut off your circulation. Here, our extensive guide on how to determine the perfect ring size for your engagement or wedding ring. Because your ring sizing should never be a guessing game.

Ring Sizing Basics

Determining band fit can actually be one of the most complicated parts of the engagement ring process because several different components impact measurement and sizing.

Environment and activity. According to Taylor Lanore, diamond consultant and engagement ring designer for Lauren B. Fine Jewelry and Diamonds, temperature, diet, pregnancy, and other biological elements can impact your fingers. "Don't be afraid if your finger changes size; that means you're alive," says Lanore. "It can change from activity, season, and so many personal factors. There's not really a formula to pick the correct ring size across the board because everyone is so different and it depends on their lifestyles."

Finger shape. Yes, there are different kinds of fingers, and they can impact ring size and fit. If you have a tapered ring finger, it widens downward toward the base, which is where your ring will fit the tightest. Rings can easily fall off tapered fingers if they slide up, so it's incredibly important to have a snug fit. On the other hand are knotted fingers where the knuckle in the middle of the finger is the widest part, which the ring has to fit over. However, the ring might move around and fit too loosely at the base of your finger. In this case, consider getting sizing beads added to your sparkler. These small add-ons stay on the bottom of the inner ring close to your hand and act like pressure points to keep the ring in place. They're incredibly easy to put on and remove.

Band width. According to David Borochov, manager of R&R Jewelers in New York City, rings with thinner bands tend to run a bit larger, whereas thicker rings have a more snug fit. The more metal around your finger, the more space it takes up and the tighter it fits. "A thin size 6 ring will not fit the same as a thick size 6 ring," says Borochov. If you have your heart set on a thin, delicate band (super trendy right now!), then opt for a slightly smaller ring size (pro tip: thinner bands make the center stone stand out more).

International Ring Sizing

In the United States and Canada, ring sizes range from 3 to 13, which includes half and quarter sizes. The sizes are measured in inches or millimeters based on the ring's diameter or circumference. The diameter measures the inside length of the ring, whereas circumference measures the length of the entire band. International ring sizing involves the same measurement process, but the numbered sizes run on different scales, which vary by country. Australia and the United Kingdom actually use an alphabetical letter sizing system.

When to Measure Ring Size

Believe it or not, your ring finger measuring conditions need to be just right. Warm weather makes our fingers swell, and they tend to shrink from cold weather in the winter. Lanore says to avoid eating salty foods, drinking hot cocktails, or performing any strenuous activity before measuring because these can all make your fingers swell. "You want your body temperature to be normal and natural," she says. Your fingers can also be swollen when you first wake up, so it's best to get measured around the middle of the day at room temperature for the most accurate, comfortable fit. In the summer, Borochov recommends couples take a few minutes to cool down before getting measured, especially if they've been outside in the heat for long periods of time.

How to Measure Yourself

If you want to take matters into your own hands (er, fingers), you can use a few different at-home measurement methods with our printable size guide, which features both diameter and circumference for each ring size.

Paper Technique: Wrap a thin piece of paper around your ring finger, keeping it close to your knuckle where an engagement ring would realistically hit (you can also use string, but it's less reliable since it's super thin and more likely to move around). Don't wrap too tight; make sure the makeshift ring fits comfortably. Use a pencil to mark the spot on the paper where the ends overlap. Measure the length of the paper against a ruler and compare the measurement to the circumferences on the size guide for your ring size.

Printable Ring Sizer Technique: Print and cut out the ring sizer at the bottom of the size guide. Make sure that the guide is printed to scale by measuring the above diameters against a ruler for accuracy. Cut the slot marked at the end of the sizer, wrap it around the base of your left ring finger, and slide the pointed end through the cut. Gently pull until it fits securely. Check the number displayed on the sizer for your ring size.

Ring Technique: Grab a ring you already own that fits the ring finger on your left hand and place it against a ruler. Measure the inner diameter of the ring and compare the measurement to the size guide. Or, print the guide to scale and place the ring directly on top of the ring images to find a matching diameter and ring size that lines up perfectly.

How to Get Professionally Measured

If you don't trust your own judgement, don't worry. You can always turn to a professional jeweler for an accurate engagement ring measurement (some things are just better left to the pros). Borochov says to be wary of at-home measuring methods, anyway, as they aren't always completely accurate. Most jewelers use sizing rings, a large keychain with a set of rings in each size that you can try on in-house to quickly determine the most reliable fit. The type of sizing rings vary by jeweler, though. Some jewelers will have a standard set, which tend to be thicker than the average women's band size, and some jewelry shops will use sizing rings that more closely reflect their in-house designs and band widths. You can also buy your own inexpensive plastic ring sizer from Amazon for the same effect. Try to shop for rings from the same jeweler that sized you, or look to see if they have engagement ring styles similar to what you envisioned. This will help ensure that the size effectively translates onto your desired band. Keep the width of the sizing rings in mind, as well, since that could influence your band measurement.

How to Guess Your Girlfriend's Size

Even though more people now seem to involve their partners in the engagement ring selection, some still want to maintain the element of surprise before a proposal. But, if you don't know your significant other's ring size, don't fret. "It's great to have someone on the inside," says Lanore. "Talk to her mom or friends if they know about the proposal." If you don't have any resources, she recommends bringing a photo of your girlfriend where her hands are clearly visible to your jeweler. This visual of her hands can actually help them gauge a ring size range.

You can also try to base the measure off one of her current rings, but this isn't always the most foolproof method. "Some customers think taking one of their girlfriend's other rings will suffice, or even trace her ring on a piece of paper," Borochov says. "But, most women don't wear rings on their left ring finger until they get engaged, so the sizing will be off. Every finger is a little bit different." If you're completely clueless about your girlfriend's ring size, he advises turning to coworkers with similar frames and statures for a more accurate estimate.

No matter what, always try to go a few sizes up so the ring can at least fit on your partner's finger for the proposal; it really kills the mood if it's too small to slip on. You can still surprise her, and simply bring it back to the jeweler later for resizing.

Getting Your Ring Resized

Jewelers can typically alter engagement rings up to two sizes up or down, but any more than that could compromise the ring's integrity and might require the jewelry shop to make a new custom band. Also, be wary of getting an eternity band, which has diamonds around the entire band, if you don't know a precise ring size. According to Lanore, because of the diamond placement for this style, eternity bands can only be resized about a quarter size up or down if there's enough excess metal in the ring, otherwise they have to be completely remade.

It's normal to get a ring resized about two or three times, but any more than that can take a toll. "Resizing up or down more than one full size is like an earthquake for the ring," says Lanore. "Frequent resizes of any kind aren't good for the metal." Many people mistakenly believe that it's easier to resize rings smaller instead of making them larger. But, rest assured, Borochov says both processes are equally as doable, as long as you use a skilled, experienced jeweler.

Band Size Related to Carat Size

There's another common misconception that finger or ring size dictate how many carats the ring's diamond should be. "This is a rumor!" says Lanore. "It's not real. Whatever you enjoy seeing the most when you look down every day—that's the right diamond size and shape for you." Borochov concurs, saying some clients unnecessarily request smaller carats if their girlfriends have small fingers. In the grand scheme of things, it simply comes down to personal preference. Carat size has no impact on ring size, nor should the ring size influence the carat.

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