You've found the ring. You've started planning the moment. There's just one problem: you have no idea what size her finger is, and asking would give the whole thing away.
You don't have to ask. With a little planning, you can get a real measurement, or at least a good estimate to confirm before you order. Here's how.
1. Borrow a ring she already wears
The best clue is a ring that fits her comfortably on the finger she'll wear her engagement ring on. Check which hand and finger that is: her other hand can be a different size, so a ring from there is only a reference, not her size.
Once you have the ring, the most reliable step is to take it to a jeweler, who can measure it on a ring mandrel in a minute. If that isn't possible, you can measure it yourself:
- Measure the inside diameter in millimeters, edge to edge across the widest inner point, then compare it with the chart below.
- Trace the inside edge on paper with a sharp pencil, and measure the circle.
Treat a home measurement as an estimate, and confirm the fit before you order. Then put the ring back exactly where you found it.
2. Press it into soap or clay
If you only have her ring for a moment, press it gently into a bar of soap or a little modeling clay and lift it straight out. The outline gives you a rough idea of the inner circle. It's an estimate only, so it's worth showing a jeweler or confirming another way.
3. Ask the people closest to her
Her best friend, sister, or mom may already know her size, or can find out far more naturally than you can. A friend can suggest trying on rings together "just for fun."
One honest caution: the more people who know about the proposal, the harder it is to keep secret. Choose someone you trust completely.
4. Have a friend use a ring sizer on her finger
A ring sizer worn on the actual finger gives you a real measurement. AIOVO sends a free ring sizer with free shipping to the US, Canada, the UK, and Australia. No purchase is needed, and it's one per household. It arrives flat, so it's easy to keep out of sight.
Hand it to a trusted friend who can size her during a casual moment. For the best reading:
- Put it on the finger she'll wear the ring on.
- Make sure it's snug but can still slide over the knuckle.
- Measure later in the day, at room temperature, and check two or three times.
5. Find a believable cover story
If you'd rather size her yourself, give her a reason that has nothing to do with a proposal. Say you're buying a ring as a gift for your sister or mom and they have "similar hands," then use the ring sizer on her finger. Keep it light, and don't overexplain.
6. Still not sure? Talk to us
If none of these work out, don't guess. Contact AIOVO before you order, and we'll help you think through the options for the ring you have in mind.
What not to order from
Some shortcuts are tempting but aren't reliable enough to order a ring:
- Comparing her fingers with yours
- How her hands look
- Average ring sizes
Ring size chart: inside diameter to US size
If you measured the inside of a borrowed ring, use this chart as an approximate reference. Confirm the fit on her finger before ordering.
| Inside diameter (mm, approx.) | US ring size |
|---|---|
| 14.9 | 4 |
| 15.3 | 4.5 |
| 15.7 | 5 |
| 16.1 | 5.5 |
| 16.5 | 6 |
| 16.9 | 6.5 |
| 17.3 | 7 |
| 17.7 | 7.5 |
| 18.1 | 8 |
| 18.6 | 8.5 |
| 18.9 | 9 |
For a full walkthrough, see our ring size guide.
Common mistakes to avoid
- Measuring the wrong finger or hand. Size the finger she'll actually wear the ring on. Her other hand is only a reference.
- Using a ring she wears loosely or stacked. If it spins or slides around, it isn't a true reading.
- Forgetting about band width. Wider bands can feel tighter, but there's no automatic half-size rule. Try a sizer close to the band width you're choosing, and judge by comfort and knuckle clearance. Our guide to engagement ring band width explains more.
- Measuring when her hands are unusually cold, hot, or swollen. Measure when her hands feel normal, and repeat at different times to confirm a consistent fit.
Frequently asked questions
What if the ring doesn't fit?
It happens, and it doesn't ruin the moment. AIOVO offers one complimentary resize within 60 days of delivery, depending on the ring's design and whether it can be adjusted safely. Contact us before sending a ring back. You cover shipping to AIOVO; we cover return shipping after resizing. See Warranty & Resizing for details.
What if the ring is a little loose?
If it could slip off, don't keep wearing it. Contact us about resizing instead.
Can I propose before I know her size?
Yes. Some people propose first and confirm the size afterward. Just check the ring's resizing options before you order.
How long does it take to get a free ring sizer?
AIOVO ships it as soon as possible after your request, and you'll get tracking details by email once it's on its way. Delivery time depends on where you live.
Ready for the next step?
Once you know her size, the hardest secret is behind you. Request your free ring sizer to confirm it, then explore our engagement rings, each one priced as a complete ring, with the diamond and setting included.
The surprise is yours to keep.
