Ring Size Calculator
Find your ring size in under a minute. Measure a ring you own right on the screen, type in a measurement, or print a ruler, then convert instantly to US, UK and EU sizes.
Step 1. Calibrate your screen. Rest any bank or ID card against the screen (on a phone, lay the phone flat on a table and set the card on top). Drag the dashed outline until it is exactly the size of the card, then take the card away. Nothing is drawn or written in this step. Every card in the world is the same standard size, so matching it teaches the tool your screen’s true scale and makes the circle in step 2 millimeter accurate.
Enter your measurement to see your size in US, UK and EU.
Enter your measurement to see your size in US, UK and EU.
Print a ring size ruler
Lay the end of your marked strip at 0 and read the US size printed above your pen mark.
How to measure your ring size
There are two ways. If you own a ring that already fits the right finger, use the on screen tool at the top of this page. If you have no ring, measure your finger with a paper strip.
Method 1: You have a ring (on screen tool)
- Grab any bank, debit or ID card. Every card in the world is the same standard size, 85.6mm wide. The tool asks for it only to learn your screen’s true scale, because every screen shows millimeters differently. Nothing is drawn or written on anything in this method.
- Match the dashed outline to the card. In the Measure with a ring tab above, rest the card against the screen (on a phone, lay the phone flat on a table and set the card on top). Drag until the dashed outline is exactly the size of the card, then take the card away. The screen is now calibrated.
- Place your ring on the screen and match the circle. Lay the ring flat on the screen and drag until the circle exactly fills the inside edge of the ring. Your US, UK and EU sizes appear instantly.
Method 2: No ring (paper strip)
- Cut a thin strip of paper. About 10cm long and roughly as wide as a ring band (5 to 7mm). Paper beats string: string stretches while you wrap it and steals a size.
- Wrap it where a ring would sit. Around the lowest part of the finger, where the finger meets the hand. Snug against the skin but never squeezing. If your knuckle is clearly wider, wrap the knuckle too, and choose a size between the two readings so the ring can pass over it.
- Mark where the end overlaps. Hold the wrap still and draw one small pen line on the strip exactly where its end meets the layer underneath.
- Measure the strip flat, in millimeters. Unwrap it, lay it flat, and measure from the end of the strip to your pen mark. That number is your finger circumference. No ruler at home? Use the Print a ruler tab above: lay the strip at 0 and your US size is printed right above the mark.
- Enter the number in the calculator. Type it into the Finger circumference tab above for your US, UK and EU sizes. Landed between two sizes? Take the larger one.
Accuracy tips: measure at the end of the day when fingers are largest, avoid measuring cold hands (fingers shrink), and wrap two or three times, keeping the largest consistent reading.
Ring size conversion chart
| US size | UK size | EU size | Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|
| 3 | F | 44 | 14.1 | 44.3 |
| 3.5 | G | 45.5 | 14.5 | 45.6 |
| 4 | H½ | 47 | 14.9 | 46.8 |
| 4.5 | I½ | 48 | 15.3 | 48.1 |
| 5 | J½ | 49 | 15.7 | 49.3 |
| 5.5 | K½ | 50.5 | 16.1 | 50.6 |
| 6 | L½ | 52 | 16.5 | 51.8 |
| 6.5 | M½ | 53 | 16.9 | 53.1 |
| 7 | N½ | 54.5 | 17.3 | 54.3 |
| 7.5 | O½ | 55.5 | 17.7 | 55.6 |
| 8 | P½ | 57 | 18.1 | 56.9 |
| 8.5 | Q½ | 58 | 18.5 | 58.1 |
| 9 | R½ | 59.5 | 18.9 | 59.4 |
| 9.5 | S½ | 61 | 19.4 | 60.9 |
| 10 | T½ | 62 | 19.8 | 62.2 |
| 10.5 | U½ | 63.5 | 20.2 | 63.5 |
| 11 | V½ | 64.5 | 20.6 | 64.7 |
| 11.5 | W½ | 66 | 21.0 | 66.0 |
| 12 | X½ | 67 | 21.4 | 67.2 |
| 12.5 | Z | 68.5 | 21.8 | 68.5 |
| 13 | Z+1 | 69.5 | 22.2 | 69.7 |
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Ring sizing FAQs
How do I measure my ring size at home?+
Wrap a thin strip of paper or a piece of string snugly around the base of your finger, mark where it overlaps, and measure that length in millimeters with a ruler. That length is your finger circumference. Enter it in the calculator above to get your US, UK and EU sizes.
What time of day should I measure my finger?+
At the end of the day, when your fingers are at their largest. Fingers are smaller in the morning and in cold weather, so an evening measurement at normal room temperature gives the most reliable fit.
What if I'm between two ring sizes?+
Choose the larger size. A slightly loose ring can be worn comfortably (or resized down more easily), while a tight ring can be uncomfortable and hard to remove.
Can I measure using a ring I already own?+
Yes. Measure the inside diameter of a ring that fits the intended finger, straight across the widest inner point, in millimeters. Switch the calculator to "ring diameter" mode and enter that number.
Do wide bands fit differently?+
Wide bands (6mm+) fit more snugly than thin ones. If you're buying a wide band and measure between sizes, go up a half size for comfort.
Are US, UK and EU ring sizes different?+
Yes. US sizes use numbers (3 to 13), UK sizes use letters (F to Z), and EU/ISO sizes are the finger circumference in millimeters. The calculator and chart on this page convert between all three.
How does the "measure on screen" tool work?+
First you calibrate the screen by matching an on-screen outline to any bank or ID card (every card is the same standard size, 85.6mm wide). Once calibrated, place a ring that fits on top of the circle and resize it until the circle sits just inside the band. The tool reads the inner diameter and gives your US, UK and EU size. Your calibration is saved for next time.