The Sizing Guide
Getting her size right
— even without asking.
Ring sizing is genuinely solvable. Here's how to approach it — methods ranked by how well they actually work, and honest guidance for what to do if things don't go perfectly on the day.
Resizing is part of the story
Most engagement rings get resized at least once — because guessing is hard, fingers change, and getting close is genuinely good enough. Every Maison Rivelle ring includes one complimentary resize within 90 days.
Close is enough to propose
A ring that's one size off will still go on the finger for the moment that matters. She's not thinking about fit when she says yes. The perfect fit is a conversation for the day after.
When in doubt, go slightly larger
A ring that's a little large can be worn immediately while you arrange a resize. A ring that's a little small can't go on at all. Between two sizes, choose the one that gives her more options on the day.
The most common ring size for women in the US falls between a 6 and a 7. That one fact won't get you to the right ring — but it does mean that if you're completely without leads, a 6.5 is a more grounded starting point than guessing. This guide is about getting you well beyond a starting point, through methods that range from confirmed measurements to thoughtful estimates, in the order you should try them.
Start with the methods section. The covert tactics are there if you need them — most people only need one or two. And hold onto this: the size just needs to be close enough to make the moment happen. Everything after that is a detail.
Three ways to find her size. In the order worth trying them.
Some methods give you a confirmed measurement. Some give you a close estimate. Some give you a reasonable starting point. Here they are in order — with honest notes on what to watch for with each one.
Borrow one of her existing rings
If she has rings she wears regularly on her left ring finger, borrowing one briefly and taking it to a jeweller gives you a confirmed measurement rather than an estimate. A jeweller can measure the inner diameter in under a minute using a mandrel or calipers — you don't need to leave the ring with them. Take a quick photo of it on the mandrel, return it before she notices, and you have the size.
One thing worth knowing: rings worn on the right hand, or on middle or pinky fingers, don't translate directly to the left ring finger size. Right-hand fingers tend to run slightly larger. If her existing collection only gives you non-ring-finger options, the covert tactics section below covers how to adjust.
Reliability
Go to a jeweller together
If keeping the proposal a complete surprise isn't essential — or if she already knows it's coming and just not when — going to a jeweller together is the most straightforward path to a perfect fit. It's genuinely romantic: it tells her you care enough about the ring fitting beautifully that you wanted her involved in that part.
You can frame it as browsing for inspiration, looking at rings for a relative, or simply having an honest conversation about wanting to get it right. Many couples find that talking about the ring before the proposal makes the proposal itself feel more certain and more tender — not less special. And a jeweller will measure both the knuckle and the base of the finger, which matters for anyone whose knuckle is noticeably wider than their finger at rest.
Reliability
Ask someone who knows her well
A close friend, her sister, or her mother may already know her ring size — or may be able to find out naturally without it seeming strange. This works especially well when the person you're asking already has the kind of relationship where rings, jewellery, and life plans come up in conversation.
The one thing to hold in mind: the more people who know a secret, the more chances it has to travel. Ask one person. Trust them. Be clear that you'd like it kept between you. A surprise that accidentally travels back to her is still a proposal — it just lands differently.
Reliability
When none of these are possible
Go with your best read on her frame. For an average frame, US 6 or 6.5 is most common. For a slimmer frame, US 5 or 5.5. For a larger frame, US 7 or 7.5. You've seen her hands — trust your observation. A ring that's one size off is resizable. Make your best honest estimate, order it, and move forward. The ring will fit perfectly soon enough.
Getting the size without giving away the plan. What actually works.
These methods sit somewhere between a confirmed measurement and a thoughtful guess. Each one works in the right circumstances. Each one has a realistic limitation — noted honestly, so you can choose the approach that fits your situation and your relationship.
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Trace the inside of one of her rings onto paper
While she's asleep or away, place one of her rings flat on a piece of paper and trace the inner circle carefully with a fine pencil. Bring the traced circle to a jeweller — they can measure the inner diameter and convert it to a size. More reliable than photographing a ring, because camera angles distort scale in ways that are hard to correct for.
Works best with a ring she wears on her left ring finger. For rings from other fingers, adjust one size smaller for the right ring finger, more for middle or index.
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Compare her finger to yours while she sleeps
Gently rest your finger alongside hers and note where it falls — is her finger slightly smaller than yours at the first knuckle, the same, a little larger? Take that reference to a jeweller and they can give you an estimate based on the comparison. Imprecise, but it gives you a physical reference rather than a visual guess.
Accuracy within ±1 size. Best used alongside another method rather than on its own.
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Ask her to try on your ring
If you wear a ring, invite her to try it on under a casual pretense — asking her opinion on whether it suits her, or whether it looks too big. Note which finger it fits and how — that's a direct comparison point to bring to a jeweller. Simple, and often works naturally in conversation.
Worth knowing: if she's observant and the timing is delicate, she may connect the dots. Read your situation before choosing this one.
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A jewellery browse, framed as something else
Take her into a jewellery store with a plausible reason — browsing for a birthday gift for someone, looking at earrings for yourself — and at some point suggest trying on rings just for fun. Watch where they sit comfortably on her left ring finger. A natural way to get the information without asking for it directly.
Works well when the cover story is something you'd actually do anyway. Feels more genuine if you come away having genuinely looked at something for the stated occasion.
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Ask a mutual friend to find out naturally
A close friend can bring ring sizes into conversation naturally — "I'm thinking about getting myself a ring, what size are you?" — in a way that doesn't raise any flags. She reports back, the secret stays intact, and you have the number. Works particularly well when the friend already has that kind of easy, casual conversation with her about things like jewellery and personal style.
Choose someone who won't over-explain or seem overly casual. One question, naturally placed, is all it takes.
The care that goes into finding her size without her knowing — that's its own kind of love. She'll likely hear the story someday. It almost always becomes one of her favourite parts.
Ring size moves with the body. Knowing when it's largest and smallest helps you size accurately.
The same finger can vary by up to a full size across a single day — expanding with warmth and activity, contracting with cold and rest. This isn't unusual, it's simply how fingers work. It means there's a better and worse time to take a measurement, and a few things worth knowing before you rely on a size you've found from an existing ring.
Time of Day
Fingers are typically smallest in the morning, when circulation is lower and the body has been at rest. By late afternoon, after a day of movement, eating, and hydration, they're at their largest. The difference between a morning and an afternoon measurement can be up to half a size — meaningful when you're trying to get it right.
→ Mid-day gives the most representative measurement. Early morning and late evening both sit at the edges.
Temperature
Cold causes fingers to contract; warmth causes them to expand. In winter, a finger can measure a full size smaller than in summer. A ring sized comfortably in January may feel tighter in August. If you're proposing in summer and sizing in winter, it's worth telling the jeweller — they can suggest sizing slightly up to account for the seasonal difference.
→ Size in conditions similar to how she'll wear the ring day to day.
Hydration & Diet
Sodium causes the body to retain fluid, which shows up in the fingers. A salty meal can add noticeable temporary size; dehydration takes it away. Neither reflects how her fingers actually sit on an ordinary day. A measurement taken at normal hydration, without a recent high-sodium meal, gives the most accurate everyday reading.
→ Normal hydration, no recent salty food. That's the everyday baseline.
Dominant Hand
The dominant hand is typically half a size to a full size larger than the other. Most engagement rings are worn on the left hand. If she's right-handed, her left ring finger will usually run slightly smaller than her right — which matters when you're using an existing right-hand ring as your reference and need to adjust accordingly.
→ Right-handed: expect the left ring finger to run about ½ size smaller than the right.
A note on knuckles: some people have a knuckle that's noticeably wider than the base of their finger. A ring sized to slide comfortably over the knuckle will spin at the base; one sized for the base won't pass the knuckle at all. If this is her situation — you can usually tell by looking at how her existing rings sit — mention it when ordering. Sizing beads or a comfort-fit band are both practical solutions that your jeweller can advise on.
Every country uses a different system. Here's how they all map to each other.
If she has rings from outside the US, or if you're looking at a size from a UK or European brand, the numbering systems are entirely different and don't convert intuitively. The table below covers the most commonly used systems. The highlighted rows show the range where most women's ring finger sizes fall.
| Diameter (mm) | US / Canada | UK / Australia | Europe (ISO) | Japan | Circumference (mm) |
|---|---|---|---|---|---|
| 14.1 mm | 3 | F | 44 | 4 | 44.2 mm |
| 14.5 mm | 3½ | G | 45½ | 5 | 45.5 mm |
| 14.9 mm | 4 | H | 47 | 7 | 46.8 mm |
| 15.3 mm | 4½ | I | 48 | 8 | 48.0 mm |
| 15.7 mm | 5 | J½ | 49½ | 9 | 49.3 mm |
| 16.1 mm | 5½ | K½ | 51 | 11 | 50.6 mm |
| 16.5 mm | 6 | L½ | 52 | 12 | 51.9 mm |
| 16.9 mm | 6½ | M½ | 53½ | 13 | 53.1 mm |
| 17.3 mm | 7 | N½ | 54½ | 14 | 54.4 mm |
| 17.7 mm | 7½ | O½ | 56 | 15 | 55.7 mm |
| 18.1 mm | 8 | P½ | 57 | 17 | 57.0 mm |
| 18.5 mm | 8½ | Q½ | 58 | 18 | 58.3 mm |
| 18.9 mm | 9 | R½ | 59½ | 19 | 59.5 mm |
| 19.4 mm | 9½ | S½ | 61 | 21 | 60.8 mm |
| 19.8 mm | 10 | T½ | 62 | 22 | 62.1 mm |
Highlighted rows (US 6–7) cover the most common range for women's ring fingers. Diameter measurements are approximate. When converting across systems, measuring inner diameter in millimetres directly from a ring is more reliable than converting through multiple systems.
The most reliable approach when converting: measure the inner diameter of an existing ring in millimetres — a ruler or calipers both work — and find that diameter in the table. This bypasses the conversion entirely and gives you a number your jeweller can use directly, in any system.
What to do if the ring doesn't fit. Which is more common than you'd think — and completely fine.
A meaningful number of engagement rings don't fit perfectly on the day they're given. The story of the ring that was a little too large or a little too small is one many couples tell warmly for years afterwards. It doesn't change what she said. It doesn't change the moment. It just adds one more chapter to the beginning of the story.
If it's too small
The ring won't go over her knuckle.
Hold the ring in your hand and let the moment happen anyway. The proposal lives in what you say and what she answers — not in whether the ring is on the finger. Put it on her right hand or a different finger for the photos. She'll have it on the right finger very soon, and a much better story to tell about the day.
→ Get in touch the day after. We'll send a prepaid label and have it back to you within 5–7 business days.
If it's too large
The ring slides or spins on her finger.
She can wear it immediately — which is the happier of the two scenarios. For the short term, wearing another ring on the same finger adds enough friction to keep it in place. A small piece of tape on the inside of the band also works as a temporary fix. She can wear it and love it while the resize is arranged.
→ Get in touch whenever you're ready. A ring that runs large is the easier adjustment.
Our resize policy: every Maison Rivelle ring includes one complimentary resize within 90 days of delivery. We handle it by mail — a prepaid label goes out to you, and the ring comes back within 5–7 business days of us receiving it. Most rings can be adjusted up or down by two sizes without any structural impact. For pavé and eternity settings, there are a few more considerations — we'll walk you through those when you reach out, based on your specific ring.
The only thing that actually matters on proposal day
The ring being the perfect size on the day you propose is a lovely detail. The fact that you chose this person, found a ring that felt right for her, and built a moment around asking the most important question you'll ever ask — that is what the proposal is. We're here to handle the rest.
We're here.
A question this guide didn't answer?
Just ask us.
If you have a specific sizing question, a ring you've already ordered, or a situation that feels a little outside the ordinary — reach out. We respond within one business day.
