Tips for Finding Someone’s Engagement Ring Size — Without Them Knowing

Planning a surprise proposal? Congrats — and smart to think about ring size ahead of time. As a goldsmith, I’ve helped many clients pull off surprise proposals. Below is an honest, practical guide with stealthy methods, how accurate they are, and what to do if you miss the mark. Read on below on tips for finding someone's engagement ring size without them knowing (from an experienced goldsmith).

A Quick Ethical Note

A surprise proposal is romantic for many people — but it’s still important to respect boundaries and privacy. Avoid sneaky actions that could feel invasive (don’t go through drawers or private files). If you think the person might not want a surprise or you’re unsure about their comfort with jewelry, consider asking indirectly (or proposing together). Okay — now the practical tips.

Here Are The Real Tips for Finding Someone’s Engagement Ring Size — Without Them Knowing (Stealth Methods & Non-Stealth Methods)

-Stealth Methods (what they are, how to do them, and accuracy)

1) Borrow a ring they already wear (best method)

• How: “Borrow” a ring they wear on their ring finger (e.g., to clean it, photograph it, or as part of a wardrobe task).

• What to do: Take it to a jeweler or place it on a ring-sizing mandrel. Or trace the inner circumference on paper.

• Accuracy: High (if it’s worn on the correct finger).

• Stealth rating: High.

2) Trace the inside of a ring

• How: Place the ring on a piece of paper and carefully trace the inside edge with a pen.

• What to do: Measure the circle’s diameter with a ruler and convert to a ring size using a chart.

• Accuracy: High (if traced cleanly).

• Stealth rating: High.

3) Measure ring’s inner diameter with calipers or a ruler

• How: Measure the inside width (mm).

• What to do: Use a ring-size conversion chart (mm → US size).

• Accuracy: Very high.

• Stealth rating: Medium–High (requires access to a ring).

4) Compare with your own rings or a printable sizing chart

• How: If they have other rings (on other fingers), compare widths against a printable ring-size chart or one of your rings.

• Accuracy: Medium (different fingers differ in size).

• Stealth rating: High.

5) Enlist a close friend or family member

• How: Ask someone close to them to casually try to find out the size or to bring the topic up in conversation (“I’m thinking of buying you something—what size do you wear?”)

• Accuracy: Variable, dependent on honesty and the friend’s sleuthing.

• Stealth rating: High.

6) Pretend to shop (low-key store visit)

• How: Suggest a casual trip to a jewelry store “just to look” and have them try on rings. You can ask the salesperson to record sizes or pick up clues for design preferences. Or let a friend take them.

• Accuracy: High.

• Stealth rating: Medium (requires interaction).

7) Use a ring sizer app or online tool

• How: If you can borrow a ring briefly, some apps let you take a picture of the ring on a reference card and estimate size.

• Accuracy: Medium.

• Stealth rating: High.

8) Buy a temporary/adjustable ring as a placeholder

• How: Purchase an inexpensive adjustable ring or an open band that’s easy to size. Use it for the proposal, then present the real ring later.

• Accuracy: N/A (this is a workaround rather than sizing).

• Stealth rating: Very High.

9) Estimate based on height/hand size (the absolute last resort)

• How: Use average-conversion charts (e.g., female average sizes cluster around 5–7 US, male around 8–11 US). Combine with visual observation of finger proportions.

• Accuracy: VERY Low. Use only if the design can be resized later (some ring designs cannot be resized after they're made) or buy a placeholder.

• Stealth rating: Very High.

-Non-Stealth Methods (Direct, Reliable)

1) Go to a jeweler to have the finger professionally sized

• How: Make an appointment (or pop into a jeweler) and have them fit your partner with a proper ring sizer. This is the most reliable way to get an exact size because the jeweler uses calibrated mandrels and assesses finger width, temperature, and band style.

• Accuracy: Very high.

• Stealth rating: Low — this is an open approach, best when you’re proposing together or when a surprise isn’t essential.

• Best use: When you want guaranteed accuracy and immediate professional advice about band width, comfort fit, and resizing options.

2) Order a ring sizer online and have them try it on

• How: Buy a physical ring-sizing kit and have your partner try it on casually (“I ordered this for fun/for a costume”), or give it as part of a joint shopping moment. Kits are cheap and usually include a range of sizes.

• Accuracy: High (when used correctly).

• Stealth rating: Low–Medium. Not stealthy if you present it directly, but useful when surprise isn’t necessary.

• Best use: When you want a private, accurate measurement at home without visiting a store; handy if you plan the purchase together.

Expert Sizing Tips & Tolerances

• Resizing is common. Most plain bands can be resized up or down 1–2 sizes. Intricate settings, eternity bands, and some metals (titanium, some platinum styles) are harder or more expensive to resize.

• Wider bands fit tighter. If you choose a wide band (wider than 2.5mm), size up slightly (a half-size or so).

• Comfort fit vs. standard fit: Comfort-fit interiors feel slightly looser — consider that when sizing.

• When in doubt, go slightly larger. A ring too tight is an immediate problem; one that’s slightly large can often be temporarily tightened (ring guards) until resizing.

• Plan for seasonal differences. Fingers will swell in heat; measure when they’re at a normal temperature.

What to do if You Guessed Wrong

• Make the moment about the promise, not the fit. If it doesn’t fit perfectly on the day, that’s fixable! Just focus on the surprise and the meaning behind the ring.

• Use a temporary ring guard. Ring guards can reduce the ring size without taking the ring to a jeweler. I love these things! I would suggest these from Amazon:

  

  
  

Quick FAQ

Q: Can you size a ring from a photo?

A: Honestly- no. It is nearly impossible to get an accurate read on the size of a ring based off of a photograph. This is due to varying screen sizes, and lack of size reference.

Q: Is it rude to ask their friends?

A: Not at all! Most close friends/family are delighted to help with a proposal and will be discreet.

Q: How long does resizing take?

A: Varies by jeweler and complexity. Simple resizing can take days; complicated jobs may take longer. (If timeline matters, mention it when working with your jeweler.)

I'm Here to Help!

If you want help pulling off the surprise, I do confidential sizing help and can work with photos or a borrowed ring to confirm size — and I'll explain resizing options up front so you’re covered if sizes don’t match perfectly on the day.

If you purchased a ring from me and need it resized, just send an email to bling@exodusgoldsmiths.com! I'll send you instructions on how to get the ring back to my shop and a repair slip to print and include in the package. Just pay for shipping, and I'll resize the ring for free within the warrantied timeframe. However, some designs cannot be resized and will need to be remade entirely instead. If this is the case, I'll send you a quote to remake the ring before proceeding.

Want a sizing chart or a printable ring-trace template? Fill out your email below and I will include a printable PDF with diameter-to-size conversions and a tracing template!