Ring sizer
30-second setup: match a card, then measure
Accurate for this screen
Hold the card flat against the screen, one corner on the outline's top-left corner, and press + or − until the outline matches the card's edges exactly.
For a laptop or monitor whose size you know. Enter the diagonal as sold — 13.3, 15.6, 24, 27. A card is more accurate, because the advertised size is rounded.
Kept on this device only
Lay the ring flat on the circle. Press + or − until the circle just fills the inside of the ring.
Ring size
- India
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- US
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- UK
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- EU
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- JP
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Already know a size? Convert it
No ring to measure? Print a sizer
A strip to wrap round the finger, discs to lay a ring on, and a 100 mm bar to check the print scale.
Ring sizer — find your ring size on screen
Put a ring that fits on the circle, grow or shrink the circle until it just fills the inside, and read the size in five systems at once.
The short answer
To find a ring size online, calibrate the screen with a bank card, then lay a ring that already fits on the on-screen circle and adjust the circle until it exactly fills the inside of the ring. The inner diameter gives the size in every system: 16.5 mm is Indian size 12, US 6, UK L½ and EU 52. Size the finger the ring will be worn on, and if the result falls between two sizes choose the larger, especially for a wide band.
Four steps to the right size
Step 1: Calibrate with a card
Hold any bank card against the screen and match the outline to it. It takes a few seconds and is remembered on this device.
Step 2: Lay the ring on the circle
Use a ring that fits the right finger. Rest it flat on the screen, centred on the circle.
Step 3: Match the inside edge
Press + or − until the circle just fills the inside of the ring — no gap inside, none of the circle hidden under the metal.
Step 4: Read every size
The result shows the Indian, US, UK, EU and Japanese size together with the diameter in mm, which is the number to give a jeweller.
Indian ring sizes in mm, US, UK and EU
One row per Indian size. The diameter and circumference are exact; US, UK and Japanese sizes are the nearest named size, since the scales do not line up.
| India | Diameter | Circumference | US | UK | EU | Japan |
|---|---|---|---|---|---|---|
| 4 | 14.01 mm | 44 mm | 3 | F | 44 | 4 |
| 5 | 14.32 mm | 45 mm | 3¼ | F½ | 45 | 5 |
| 6 | 14.64 mm | 46 mm | 3¾ | G½ | 46 | 6 |
| 7 | 14.96 mm | 47 mm | 4 | H | 47 | 7 |
| 8 | 15.28 mm | 48 mm | 4½ | I | 48 | 8 |
| 9 | 15.60 mm | 49 mm | 5 | J½ | 49 | 9 |
| 10 | 15.92 mm | 50 mm | 5¼ | K | 50 | 10 |
| 11 | 16.23 mm | 51 mm | 5¾ | L | 51 | 11 |
| 12 | 16.55 mm | 52 mm | 6 | L½ | 52 | 12 |
| 13 | 16.87 mm | 53 mm | 6½ | M½ | 53 | 13 |
| 14 | 17.19 mm | 54 mm | 6¾ | N | 54 | 14 |
| 15 | 17.51 mm | 55 mm | 7¼ | O | 55 | 15 |
| 16 | 17.83 mm | 56 mm | 7½ | O½ | 56 | 15 |
| 17 | 18.14 mm | 57 mm | 8 | P½ | 57 | 16 |
| 18 | 18.46 mm | 58 mm | 8½ | Q½ | 58 | 17 |
| 19 | 18.78 mm | 59 mm | 8¾ | R | 59 | 18 |
| 20 | 19.10 mm | 60 mm | 9¼ | S | 60 | 19 |
| 21 | 19.42 mm | 61 mm | 9½ | S½ | 61 | 20 |
| 22 | 19.74 mm | 62 mm | 10 | T½ | 62 | 21 |
| 23 | 20.05 mm | 63 mm | 10¼ | U | 63 | 22 |
| 24 | 20.37 mm | 64 mm | 10¾ | V | 64 | 23 |
| 25 | 20.69 mm | 65 mm | 11¼ | W | 65 | 24 |
| 26 | 21.01 mm | 66 mm | 11½ | W½ | 66 | 25 |
| 27 | 21.33 mm | 67 mm | 12 | X½ | 67 | 26 |
| 28 | 21.65 mm | 68 mm | 12¼ | Y½ | 68 | 27 |
| 29 | 21.96 mm | 69 mm | 12¾ | Z | 69 | 28 |
| 30 | 22.28 mm | 70 mm | 13 | Z | 70 | 29 |
Indian size = inner circumference in mm − 40. US diameter = 11.63 mm + 0.8128 mm × size. Jewellers' own charts differ by up to a size, so when ordering, give the diameter in mm as well.
What changes a ring size
Match the inside, not the outside
A ring size is the hole, not the band. A thick ring can be 3 mm wider on the outside than the size it actually is.
Between sizes, go up
A slightly loose ring can be worn and cheaply tightened; a tight one cannot be worn at all. Wide bands — 6 mm and over — sit tighter, so go up half a size for those too.
Fingers change through the day
They are smallest in the morning and in the cold, largest in the evening and the heat. Size a ring that feels right in the evening.
Give the jeweller the millimetres
Jewellers' charts differ from each other by up to a size. The inner diameter in mm means the same thing on every chart, so quote it alongside the size.
One number, kept on your device
The calibration is a single figure — pixels per millimetre for this screen — stored in your own browser. Nothing you measure is sent anywhere, and there is no account. The margin of error is shown beside every result, because a tool that hides it is guessing on your behalf.
- No upload, no account, no email
- Calibrate once for every measuring tool here
- Margin of error shown for your own screen
- Warns you when browser zoom would make it wrong
- No ads beside the ruler or the sizing circles
Questions people ask
Anything we've missed?
How accurate is an on-screen ring sizer?
After calibration the circle is true to about one pixel, which is around half an Indian size on a phone and a little more on a laptop. That is good enough to choose between neighbouring sizes, and the page shows the margin for your own screen. For an expensive or non-returnable ring, confirm with the jeweller or the printable sizer as well.
What if I do not have a ring to measure?
Use the printable ring sizer on this page: a paper strip that wraps round the finger and reads the size at a slot. Print it at 100%, check the 100 mm bar on the sheet with a ruler, and pull the strip snug over the knuckle, not just the base of the finger.
How do Indian ring sizes work?
An Indian ring size is the inner circumference in millimetres minus 40. Size 12 is a 52 mm circumference, which is 16.5 mm across. Each size up adds 1 mm of circumference, about a third of a millimetre of diameter.
Is my Indian size the same as my US size?
No. Indian size 12 is about US 6, Indian 14 is about US 6¾ and Indian 18 is about US 8½. The chart on this page converts every size, and the converter above the chart does it for one size at a time.
Can I find someone's ring size secretly?
Yes — borrow a ring they wear on the same finger and lay it on the circle here; it takes under a minute. Make sure it is from the right finger and hand: the dominant hand is usually about half a size larger.
Why do I have to calibrate first?
Because a browser does not know how big your screen is. Web pages assume 96 pixels to the inch, and almost no real screen matches that, so an uncalibrated on-screen ruler can be out by 30% or more. Matching an outline to a bank card once tells the page how many pixels make a millimetre on your screen.
Do I have to calibrate every time?
No. The calibration is kept on this device, in this browser, and every measuring tool on Spolvero uses it. You are asked again only if the browser zoom changes, because zoom changes the size of everything on the page.
Is anything uploaded?
No. The calibration is one number stored in your own browser. Nothing you measure is sent anywhere, and the tools work with the connection switched off once the page has loaded.
Guides worth reading
- Measuring
ATM and credit card size in cm, mm and inches, and how to use a card as a ruler
Every ATM, debit and credit card is 8.56 × 5.398 cm (85.6 × 53.98 mm, or 3.370 × 2.125 inches). How to measure with one and set a screen ruler.
5 min read - Ring size
How to find someone's ring size secretly: five ways that work
Five ways to get a partner's ring size without asking, from borrowing a ring for a minute to asking a friend, ranked by accuracy, with mistakes to avoid.
6 min read - Ring size
Indian ring size chart, with US, UK and EU sizes side by side
What an Indian ring size measures, the full conversion to US, UK and EU sizes with diameters in mm, and why two jewellers' charts can disagree by a size.
6 min read
More to measure
Online Ruler
Match the outline to a bank card once, and the ruler below is true to size on this screen.
Bangle Sizer
Lay a bangle that fits on the circle and match it to the inside edge, or measure round your hand with the thumb tucked in.
Indian Ring Size Chart
Every Indian ring size with its diameter in millimetres and the US, UK, EU and Japanese size beside it.
Poster Maker
Print any picture wall-sized on A4 or Letter, at a true scale you can check with a ruler.
See everything on the Measure page.