How to Find Her Ring Size Without Her Knowing

Getting the ring size wrong doesn't ruin a proposal — but knowing you have a reasonably accurate size going in means one less thing to worry about on the day. Here's what actually works, roughly in order of how reliable it is.

Borrow a ring she already wears on that finger

If she wears any ring — even a fashion ring, even on the "wrong" hand — on the ring finger specifically, that's your most accurate source. Take it to a jeweller (most will size it for free or for a small fee) rather than guessing from a printable ring sizer at home, which is easy to get wrong by half a size depending on paper stock and printer scaling. Put the ring back exactly where you found it.

Recruit someone she trusts

A close friend, sister or parent can often just ask her outright, frame it as their own idea ("I'm thinking of getting a ring, what size are you? Let's compare"), or borrow a ring on your behalf without raising suspicion the way you asking directly might. This is usually the single easiest option if you have someone reliable to ask.

Use a jeweller's estimate from another piece of jewellery

Some jewellers can give a rough estimate from a ring worn on a different finger, adjusted for typical size differences between fingers — it's less precise than sizing the actual ring-finger ring, but better than a pure guess.

If you genuinely can't find out

Guess slightly larger rather than smaller — a ring that's a touch loose can be worn on a chain or resized more easily and cheaply than one that doesn't fit at all on the day. Buying loose (rather than pre-set) and having a local jeweller size the setting after the proposal, once you know the real size, is a completely normal path — see Buying a loose diamond for a bespoke engagement ring.

What to do if you guessed wrong

Almost every jeweller resizes rings as a matter of course, and it's a routine, inexpensive job for most standard bands. The moment matters far more than the exact fit on the day — a resize afterwards is normal, not a failure.

Related reading

• Should you buy the diamond or the ring first?
• Buying a diamond for an engagement ring: where to start
• Ring Settings Guide: Prong, Bezel, Halo & Pavé Explained