Engagement Ring Sizing Guide: How to Guess Her Ring Size and Keep it a Secret
Planning a surprise proposal is thrilling–but figuring out your partner's ring size without them finding out can be the trickiest part before you go ring shopping for a diamond engagement ring.
You want the magical moment to unfold seamlessly with a perfect engagement ring that slips on effortlessly. Whether you’re borrowing clues or doing a little detective work, there are clever (and discreet) ways to discover the right ring size without spoiling the surprise.
Borrow a Ring They Already Wear
One of the simplest ways to estimate the right ring size is to borrow a different ring your partner already wears on their ring finger (or one that fits a similar finger on the opposite hand). Take it to your jeweler for measurement or, if that’s too risky, trace the inner circle on paper or use a small ruler to measure the diameter of the ring in millimeters.
Keep in mind that the dominant hand fingers can sometimes be a slightly larger size, so a jeweler can make a small adjustment (like a half size) if needed for an engagement ring on the left hand.
Compare Hands
Comparing hands may sound unscientific, but it can help! If your finger size or hands are similar in size as your partner, try sliding one of their rings onto your finger to see where it fits. The jeweler can use that point as a reference—perhaps it fits your pinky or halfway down your ring finger—and translate that into an accurate estimate.
Try the String or Paper Strip Method
If you have the opportunity to measure your partner’s finger directly while they’re sleeping or distracted (and you’re confident they won’t notice!), wrap a small piece of string or a thin strip of paper around the base of their ring finger. Mark where the ends meet, then measure the length in millimeters.
Compare that measurement to a ring size chart—most jewelers can convert it instantly into the correct size. Be gentle and don’t pull the string too tight—it should fit snugly but still be able to slide comfortably over the knuckle.
Use a Printable Ring Sizer
Many jewelers offer printable ring sizers online that let you match an existing ring to a series of circles, or measure with a paper strip that works like a mini tape measure. This can be done at home—and best of all, it’s easy to hide your research afterward! You could also order a plastic ring sizer online to measure ring size.
Ask a Friend or Family Member for Help
A best friend, sibling, or family member can often help you solve the mystery. They may already know your partner’s ring size or can casually do a shopping trip where your partner tries on rings “just for fun.” The key is keeping it light and natural so your secret stays safe.
Consider the Average Ring Size
When all else fails, statistics can help. The average women’s ring size is typically between size 6 and 7, while the average men’s ring size is around 9 to 10. If your partner has slender fingers, you might guess slightly smaller (around 5 or 5.5), and if they’re taller or have larger hands, a size up (around 7.5 or 8) might be closer.
Keep Knuckle Size in Mind
Knuckle size can affect the perfect fit more than you might think. If your partner has larger knuckles and slimmer fingers, the ring should slide over the knuckle without spinning loosely once it’s on. If you’re unsure, aim for a comfortable middle ground; jewelers can fine-tune the fit after the proposal to balance comfort and security.
When in Doubt, Size Up Slightly
It’s always better to go a little larger than too small—resizing down is far easier than making a ring bigger. Many engagement ring styles can be resized by one to two sizes without compromising design or gemstone placement.
Some Settings Are Easier to Resize Than Others
Not all engagement ring settings can be resized with the same ease. Simple designs—like solitaires or classic settings with plain metal bands—are usually the easiest to adjust. Jewelers can gently cut and reshape the band without disturbing the diamond or weakening the setting.
More intricate rings, however, can pose a challenge. Eternity rings, where diamonds or gemstones wrap entirely around the ring, are very difficult (and sometimes impossible) to resize without altering the design.
Likewise, wedding rings that have pavé settings or bands with delicate engravings, milgrain edges, or tension-set stones require extra care or alternative solutions like adding sizing beads or inserts. Displayed is a pave setting, a milgrain edged mens wedding band, and a tension set ring.
A wide band will be harder to resize than a thin band. If choosing a wide band, it’s wise to size up slightly (like a half size). Comfort-fit wedding bands are slightly rounded inside and will require extra care during resizing to maintain their smooth interior contour.
The type of precious metal also matters–gold and platinum resize cleanly and are forgiving for adjustments. Rose gold, due to its copper content, can be trickier—it’s more prone to cracking if reshaped too often. Titanium and tungsten rings typically can’t be resized at all because of their hardness.
If you’re choosing a ring before knowing the exact size, a solitaire, halo, or three-stone ring with a plain back offers flexibility for easy resizing after the proposal.
Use a Ring Size Conversion Chart
If you’re measuring from a ring purchased overseas or see sizes listed in the UK, Europe, you could ask your jeweler for a ring size conversion chart, or look at the one below. It helps you match the measurements perfectly to U.S. ring sizes so you don’t get lost in translation.
A Final Thought
The perfect proposal isn’t about precision–it’s about meaning. Even if the size isn't a perfect fit on day one, resizing is quick, easy, and often complimentary when done at the same jewelry store where you purchased it. What matters most is the love and intention behind your choice. The ring is a symbol of your love story together–and that’s what makes it priceless.
At E.D. Marshall Jewelers, we specialize in helping you plan the perfect surprise proposal–from discreet sizing assistance to resizing after the big “yes”. We can make subtle recommendations based on your partner’s style. If you are interested in having a custom engagement ring created, we’re able to bring your vision to life.
Whether you’re guessing from a distance, or gathering secret clues, we’ll ensure your perfect engagement ring fits beautifully and your secret stays safe. Come visit our showroom and talk to one of our professional jewelers when you are ready to begin your ring shopping journey.