Open the Measure tab and tap Ring Sizer. Place a ring that fits flat on the circle and adjust it (slider, + / − or pinch) until the circle exactly fills the inside of the ring. No ring? Choose Paper strip: wrap a thin strip of paper around the base of your finger, mark where it overlaps, put the end on the 0 line and drag the marker to your mark. You get the size in US, UK/AU letters, EU/ISO, Japan/China and Italy/Spain/Switzerland, plus the diameter and circumference.
SizeSnap knows the pixel density of every iPhone that runs iOS 17 or later, so millimetres on screen are real millimetres. To double-check — or on an iPad, a Mac, or a brand-new model — tap Check screen accuracy, place any bank or ID card (or a US quarter / 1 euro coin) on the outline and move the slider until it matches. Measured carefully, the result is within about a quarter of a ring size. Between two sizes, SizeSnap recommends the larger one. For an engagement ring, confirm with a jeweler.
SizeSnap is free. SizeSnap Pro is an optional one-time purchase (no subscription) for families: unlimited profiles on iPhone and Apple Watch, size cards you can send for gifts, and the ring measurement history. It works with Family Sharing. To restore it on a new device, tap Restore Purchases in Settings. If you bought SizeSnap while it was a paid app, Pro is already yours.
Version 1.0 converted EU to US shoe sizes one-to-one, which made US and UK sizes about one size too large above EU 42. Version 1.1 follows the major brand charts (for example, men's EU 44 = US 10 = UK 9.5), and UK ring letters now follow the British Standard (US 7 = N½). If you saved a size in 1.0, open it once and check it.
On the watch: open the Converter tab, pick a category, turn the Digital Crown to your size, then tap the row or "Save as My Size". On the iPhone: open My Sizes, tap a category, and tap your size in the list — or tap Save after measuring a ring. Saved sizes appear in My Sizes on both devices.
Long-press your watch face, tap Edit, choose a complication slot, and select SizeSnap. The complication shows the saved sizes of the profile selected under Settings → Apple Watch in the iPhone app (or your first saved size if you use only one profile). Tapping it opens My Sizes.
Yes. The watch app is fully standalone: all conversion tables live on the watch, and you can browse, convert, and save sizes without your iPhone nearby — including on cellular-only walks and trips. The iPhone app adds family profiles and bigger tables, but it is optional.
Purchases and refunds are handled by Apple, not by us. Request a refund at reportaproblem.apple.com — sign in with the Apple ID used for the purchase, find SizeSnap, and choose "Request a refund". Apple typically decides within 24–48 hours.
Email us at homasglobal443@gmail.com. We read everything and usually reply within two business days. Feature requests are welcome — several size tables in the app started as user suggestions.