Find a ring size without asking, a jeweler or a ring sizer

Option 1: measure the finger on your phone

Under the hood it's the same engine as the ring tool, just drawn as two vertical bars instead of a circle. Widen them until they sit against the sides of your finger and the app converts that gap straight into a diameter and a size.

1. Calibrate first: open Calibration, lay a ruler on the screen and move the slider until the marks match.
2. Open Finger Sizer.
3. Rest the finger flat on the screen, between the bars, at the spot where the ring will sit.
4. Drag the slider until both bars just touch the skin, without pressing into it.
5. Read the diameter, circumference and US, UK, Swiss/EU and Asian sizes, then tap Save Measurement.

Option 2: estimate with the Find My Size quiz

When you cannot measure, for example when the ring is a surprise, open Find My Size. The Ring Size Finder asks five questions: gender, body frame, height range, which finger the ring is for, and whether you already know a size. Then tap Get My Estimate.

Weight never enters the formula, unlike many size calculators out there. It starts from a baseline ring-finger size — US 10.0 male, 6.5 female, 8.0 otherwise — then nudges it up or down for frame, height and which finger, rounds to the nearest half size, and converts that to an approximate diameter.

Already know your size? Pick Yes, I know my size, type it in, and the quiz skips the guesswork entirely — US 8.5 just maps to about 18.7 mm.

The result screen is blunt about what it isn't: This is an estimate only, with buttons for Measure with Ring Sizer and Measure with Finger Sizer right underneath. Take the hint. Two people who answer identically can genuinely wear sizes a full size or more apart.

How to secretly find someone's ring size

The quiz is a first guess. A borrowed ring beats it every time, and it only has to leave the jewelry box for a minute or two. Calibrate the screen before you take the ring, so the clock only starts when you have it in hand.

Borrowed ring checklist

1. Before: open Calibration, lay a ruler on the screen and move the slider until the marks match. Do this the day before if you can.
2. Pick the right ring: one they wear on the same finger and the same hand the new ring is for.
3. Open Ring Sizer and lay the ring flat in the middle of the screen.
4. Drag the slider until the circle sits on the inside edge of the band, not the outside. The outside edge reads a size or more too big on a thick band.
5. Read the US, UK, EU and JP sizes and tap Save Measurement.
6. Put the ring back exactly where it was, the way it was lying.

When the ring is from a different finger

Only a ring from the wrong finger? The Finger Guide shows typical sizes per finger: an index finger usually runs half to one size bigger than the ring finger. Hands differ too, often by half a size. Use it to adjust, and treat the result as an estimate.

Between two sizes

Pick the larger one. A ring that is a little loose can be made smaller; one that won't pass the knuckle can't be worn at all, and the surprise is gone. A thick or comfort-fit band also feels tighter than a thin one of the same size, so check Comfort Fit Adjustment in System Converter if the new ring is wide.

When not to trust the estimate

• The borrowed ring itself doesn't fit well: they twist it off easily, or it leaves a mark.
• It sits on a different hand or finger from the new ring.
• The new ring is an eternity band or another style that can't be resized.
• You skipped calibration.

Common mistakes

• Treating the quiz result as a measured size. It is a demographic average.
• Measuring a cold finger in the morning. Fingers are smallest then.
• Skipping calibration. Every screen draws millimetres slightly differently.
• Pressing the bars into the skin. They should just touch.

Questions and answers

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• Which finger to measure for your ring size · Ring Sizer

More Ring Sizer guides

• How to measure your ring size at home with your phone
• Ring size conversion chart: US, UK, EU and Japanese sizes
• Which finger to measure for your ring size
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• Birthstone by month: a chart for all 12 months
• How to clean and care for a ring at home
• Compare two ring sizes: how big is the difference?
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• Ring no longer goes over your knuckle: which size now?
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• All questions about Ring Sizer
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