The most reliable way to find out her ring size secretly is to borrow a ring she already wears on the same finger, measure the inside diameter in millimeters (or trace the inside of the band on paper), and match it to a ring size chart. If you can't borrow one, a trusted friend or family member who knows her size, or who can help you get a ring, is the next best thing.

Here's how to do each of those quietly, which finger and hand matter, and what to do if you're still not certain.

Step 1: borrow the right ring

Not every ring she owns is useful. The best one is a ring she wears on the same finger and hand you're buying for.

Fingers on the dominant hand are often slightly larger, so a ring from her right hand may fit a touch loose on her left if she's right-handed. Use it as a guide, not a guarantee.

Also check that the ring actually fits her well. If she always twists it, takes it off because it's tight, or only wears it in winter, it may not reflect her true size.

Timing the borrow

Pick a ring she doesn't wear daily, so it won't be missed for an evening. Measure it the same day and put it back exactly where it was. Taking a quick photo of how it was stored helps.

Step 2: measure, trace or press the ring

Once you have the ring, you have a few options. Use more than one if you can.

Measure the inside diameter

Lay the ring flat and measure straight across the widest inside point, from inner edge to inner edge, with a millimeter ruler. Don't include the metal. Then match the number to the chart in our guide on how to measure ring size at home, which lists US sizes 4 to 10 with inner diameters and circumferences.

Trace it

If you can't measure right away, place the ring on a sheet of paper and trace carefully around the inside of the band with a sharp pencil. Trace the inside, not the outside, or the size will come out too big. Do it twice to check. Later, measure across the traced circle.

Press an impression

A common trick is to press the ring gently into a bar of soap or a piece of modeling clay to leave a clean impression of the inner circle. Wipe the ring afterward so there's no residue on it. You can then measure the impression at your own pace.

Slide it onto your own finger

As a backup, slide the ring onto one of your fingers and mark with a pen where it stops. A jeweler can size that point on your finger later. It's less precise than the other methods, but better than nothing.

Step 3: ask someone she trusts

Friends, sisters, her mom or a close cousin can be your best allies.

• They may already know. Close friends often know each other's ring sizes from shopping together or trying on rings.
• They can borrow a ring for you. A friend has easier access to her jewelry box, and is less suspicious.
• They can bring it up casually. "Let's try on rings for fun" on a day out is an easy way to find out her size.

Only involve people who are genuinely good at keeping a secret.

Step 4: low-key conversation ideas

If borrowing isn't possible, some indirect approaches work:

• Mention you're buying a ring for someone else (a sister, a friend) and ask her to try on a ring "to check the size."
• Notice if she's ever had a ring resized, or has a sizing receipt from a jeweler.
• If you're shopping together, wander past a jewelry counter and let her try things on.

These are less precise, but they can confirm a measurement you already have.

Why average ring sizes aren't a reliable guide

It's tempting to look up an "average" women's ring size and order that. We'd steer you away from it. Ring sizes vary widely from person to person, depending on build, hand shape, knuckle size and even climate. An average describes a large group, not the one finger you're buying for, and a half size either way is the difference between a comfortable fit and a ring that won't go over the knuckle.

A real measurement from one of her rings, even an imperfect one, is far more useful than any average.

What to do if you're still not sure

Go slightly larger, not smaller

If your measurements land between two sizes, choose the larger. A ring that's a little loose can still be worn, and a jeweler can often suggest a simple fix such as a sizing insert. A ring that's too small may not go on at all, which is a much worse moment during a proposal.

Please measure before ordering

We want to be clear about this: our returns policy does not accept returns or exchanges for incorrect sizing. Eligible, unworn items can be returned within 14 days of delivery, but wrong size is not one of the eligible reasons. So it's worth taking the time to get the best measurement you can. If you'd like a second opinion, email service@furmanluxury.com with what you've measured and the ring you're considering, and we'll help you choose before you order.

Think about resizing early

Some rings are easier to adjust later than others:

• Solitaires and simple bands can often be resized by a jeweler. Because our rings are gold-plated sterling silver, a resize may also mean re-plating, so ask your jeweler.
• Full eternity bands, with stones all the way around, generally can't be resized. If you're unsure of her size, a solitaire or a ring with stones only across the top is the safer pick. Our engagement ring guide compares styles.

Choose a design with built-in flexibility

The Promise Duo Ring is offered in three size ranges (4–6, 6.5–8 and 8.5–10) rather than one exact size, which gives you a little more leeway. Check the product page for how the fit works before ordering.

Or propose with something that doesn't need a size

Some people propose with a meaningful necklace or pendant and choose the ring together afterward. It's still a surprise, and she gets a say in the final ring.

A note on our ring sizes and timing

Most of our rings come in US sizes 4 to 10, many with half sizes, such as The Signature Ring. Some designs, like the Luna Oval Cut Engagement Ring, come in whole sizes 5 to 9, so check the options on each page.

Each piece is finished to order in up to 7 business days, and delivery then usually takes 7 to 14 business days with tracking. If you have a proposal date in mind, leave yourself plenty of time, including time to measure carefully before you order.

Ready when you are

Once you've got a size you trust, browse our engagement rings or the engagement and promise pieces in Love & Proposals. If you're thinking of a promise ring rather than an engagement ring, our post on what a promise ring means may help you decide.