When you’re planning the perfect proposal, the last thing you want is for the ring to be the wrong size. It’s a small detail that can make a big moment that you want to get right. I’m Benjamin Khordipour, a GIA-certified gemologist and vintage jewelry expert with a decade of experience helping thousands of couples find their perfect engagement ring.
1. Measure a Ring She Wears on Her Ring Finger
If she already wears a ring on her left-hand ring finger, you’re in luck. You can discreetly borrow that ring and bring it to a jeweler for professional sizing. If borrowing isn’t possible, you can still trace the ring onto paper, or press it into a bar of soap to make an impression. Alternatively, you can measure its inner diameter with a ruler or caliper.
Important Note: Keep in mind that ring sizing is “finger-specific”, which means that each finger has different dimensions. Even the same finger on the opposite hand will vary by up to half a size. So this method only works if you’re certain she wears that specific ring on the correct finger. Be especially cautious not to pick a ring from a different finger and assume it’s transferable.
Overall, this method can give an accurate result with little risk so long as you’re measuring a ring from the correct finger.
It’s low-effort and doesn’t involve anyone else, and you don’t need to order any tools online.
2. Ask Family or Friends to Investigate
Sometimes, the people closest to her already know her ring size, or they’re able to find out her size without raising suspicion. You can ask a sister, best friend, or even her mom to bring it up in conversation, put their ring on her finger, go ring shopping “for fun,” or casually try on rings during an outing. They might even stage a fake shopping trip to help you out.
That said, trust is key here. Make sure whoever you ask is discreet and doesn’t accidentally tip her off. A friend with subtlety and good acting skills will be your best asset.
This is a great method when you don’t have access to her rings and can’t measure her finger directly. It’s low-risk and keeps the surprise intact.
3. Measuring While She Sleeps (My Top Method)
If you’re not in a crazy rush (and can wait 2-3 days), this method is the best that we’ve seen and it will also be the most accurate. I recommend buying a metal ring sizer (we sell them on Etsy for $12). They’re the ring sizers that expert jewelers use for their customers.
Once the ring sizer comes, gently slide each size onto her ring finger while she sleeps. The one that fits snugly but slides off without resistance is likely the right size.
Pro tip: Warm the metal sizer to room temperature before using it, so that the cold steel doesn’t wake her up.
This method gives you the most accurate result without involving anyone else, assuming that you pull it off smoothly. It does carry the risk of waking her up, but with care and preparation, it’s a great stealthy option for committed partners.
Important Note: Although there are other techniques on the internet like using a piece of non-stretchy string, dental floss, or a strip of paper to wrap around her finger, we don’t recommend it. Additionally, the plastic ring belt, isn’t always 100% reliable.
4. Use Another Ring and Extrapolate
If she doesn’t wear a ring on her left-hand ring finger, you might still be able to get an estimate by analyzing other rings she owns. Check her jewelry box or take note of the rings she wears daily. Even if they’re for different fingers, they can provide clues, especially if you know which hand and finger each ring fits.
For example, if she wears a ring on her right-hand ring finger, and she’s right-handed, that finger is often slightly larger due to muscle use (usually by half a size to a full size). Middle fingers tend to be even larger, while pinkies are much smaller. Take all of that into account when estimating the size for her left-hand ring finger.
While this approach isn’t the most precise, it’s better than guessing blindly. Think of it as a last resort or a complementary tactic when combined with another method. Just be cautious not to overestimate if you’re working from a larger finger size.
5. Take a Guess Based on Her Hand Size
When all else fails, it’s possible to make an educated guess based on the size and shape of her hand. Most women in the U.S. fall between ring sizes 5 and 7, with 6 being the most common. If you’ve seen her friends’ hands and know their sizes, you can compare and get a sense of where she might fall.
Another trick is to hold her hand and compare her ring finger to one of your own (like your pinky finger). If your pinky is smaller than her ring finger, you’ll have a starting rough-estimate of her size. While not scientific, this method can get surprisingly close if done carefully.
6. Discreetly Measure Her Finger During Daily Tasks
You can get creative by guiding her into doing an activity that naturally makes an impression of her finger. For example, ask her to help you plant seeds in the garden and gently press her ring finger into the soil. Or give her a craft project or toy that requires inserting fingers into a mold-like shape.
Afterward, you can discreetly examine or measure the impression left behind. While this idea may feel a bit MacGyver-esque, it works for partners who are observant and quick-thinking. It’s especially useful if you live together or share activities that allow for spontaneous measurement opportunities.
This approach definitely isn’t for everyone, but for hands-on couples, it can be a fun and subtle way to gather sizing info. It works best when done playfully and without making her feel like she’s being observed.
7. Ask for Size Far in Advance
One of the simplest and most overlooked strategies is to ask her directly for her ring size.
The trick is to ask well before the proposal is on her radar. You can casually bring it up during a conversation about future plans or even while discussing jewelry in general. Another great approach is to order a metal ring sizer and ask her to measure her finger “just in case” or “for some future date.”
The key here is timing. If you bring it up a month or more before your actual proposal, the element of surprise will almost certainly still be there. By the time the big moment arrives, she’ll have forgotten all about it, or at least she won’t suspect the timing.
This method gives you a perfect measurement without the risk or guesswork, and it still allows you to plan a thoughtful, meaningful surprise. Plus, asking in advance shows that you’re thoughtful and planning ahead, qualities she’ll likely appreciate just as much as the ring itself.
Frequently Asked “Finger Size” Questions
1. How accurate does the engagement ring sizing need to be for the proposal?
You don’t need to get the ring size perfect, as being within half a size is usually good enough for the proposal.
Once the proposal is over, most jewelers will usually adjust the ring for free if it’s slightly too big or too small.
What matters most is that the ring can go on her finger during the proposal without being uncomfortably tight or way too loose that it will fall right off. If you’re unsure, it’s usually better to size slightly larger, since it’s easier to resize down than to stretch a ring up.
2. Can engagement rings be resized later?
Yes, most engagement rings can be resized by one or two sizes without any issues. Rings with plain shanks are the easiest to adjust, while designs with intricate filigree, side stones, or eternity bands will have more limitations. Some rings will not be able to be resized.
It’s best to consult with the jeweler to avoid damaging the ring’s structure or aesthetics during resizing.
3. What if I get the size completely wrong?
If the ring doesn’t fit at all, don’t panic.
Most jewelers will offer one free resizing or will at least help you exchange the ring for the correct size. The key is to stay calm, keep the mood light, and let her know that the ring can be adjusted. Most partners are so touched by the proposal that they won’t mind a quick trip to the jeweler afterward.
4. When guessing her finger size, is it better to go big or small?
If you have to make an educated guess, always go slightly larger. A ring that’s too small may not go past her knuckle during the proposal, which can feel frustrating or anticlimactic. A slightly larger ring can at least be placed on her finger and admired, even if it is spinning around a bit. Plus, as mentioned above, resizing down is usually much more simple.
5. Can I resize a ring with side stones or vintage detailing?
Resizing a ring with side stones, filigree, or vintage engraving can be more complex and may require a specialist.
In some cases, resizing too much can distort the design or loosen the settings. However, a skilled jeweler familiar with antique rings will often be able to make precise adjustments while preserving the craftsmanship.
Important Note: Always check with a vintage jewelry expert before making changes to a vintage ring.
Talk to a Jewelry Expert
Once you have her ring size, the real fun begins: choosing a ring that matches her style, personality, and your vision for the proposal. Whether you’re leaning vintage, classic, or completely custom, our collection at Estate Diamond Jewelry offers rare, handpicked engagement rings that she’ll treasure forever.
Fill out the form below, and one of our engagement ring experts will get back to you within one business hour to help you find the perfect ring.