Free Ring Size Calculator: What Is RingSize?
RingSize is a free online ring size calculator that turns your phone screen into a measuring tool. In about two minutes you can measure your ring size at home, with no printer, no app download and no sign-up. You calibrate the screen with a bank card, then either match a circle to a ring you already own or match a line to a strip of paper wrapped around your finger. The tool shows your size in US, UK, EU, Indian and Japanese ring sizes, together with the inner diameter and circumference in millimetres.
A careful measurement saves returns, resizing fees and waiting time, which is what this tool is built for.
How to Measure Ring Size at Home in 4 Steps
- Open RingSize on your phone and tap "Start measuring". Put the phone flat on a table and keep the browser at its normal zoom level.
- Calibrate your screen. Stand a bank card, or any card of the same size, upright on the screen and drag the slider until both sides of the card touch the side lines. This teaches the tool how many pixels make one millimetre on your phone.
- Choose a method: "I have a ring that fits" or "I have no ring (paper strip)".
- Adjust the slider until the circle matches the inside edge of your ring, or until the gold line meets the mark on your paper strip. Your size appears instantly, and you can switch between US, UK, EU, IN and JP.
That is the whole process. For a longer walkthrough, read our guide on how to measure your ring size at home.
How to Find Ring Size: Two Easy Methods
Method 1: Measure a ring that already fits
Take a ring that fits the finger you want to size. Place it flat on the on-screen circle and look straight down with one eye closed. Resize the circle until its edge touches the inside of the band. The diameter shown is the inner diameter of the ring, which is what ring sizes are based on.
Method 2: How to determine ring size with a paper strip
No ring? Cut a strip of thin paper about 6 mm wide and 10 cm long. Wrap it snugly around the base of your finger and mark where the end overlaps. Lay the strip flat along the gold line from the zero mark and drag the slider until the line ends at your mark. RingSize divides the circumference by pi to get the diameter, then finds your size. Use thin paper, because thick paper adds roughly half a millimetre.
Ring Size Chart: US, UK, EU, India and Japan
Ring sizes follow different systems around the world, which is why a ring size chart is useful. The US and Canada use numbers such as 5, 6 or 7½. The UK and Australia use letters such as L½ or N½. EU sizes follow ISO 8653 and are based on the inner circumference in millimetres, Indian sizes run roughly 40 below the circumference, and Japan uses a numeric scale of its own. This table shows common ring size measurements in all five systems.
| US | UK | EU | IN | JP | Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|---|---|
| 5 | J½ | 49 | 9 | 9 | 15.69 | 49.30 |
| 6 | L½ | 52 | 12 | 11 | 16.51 | 51.86 |
| 7 | N½ | 54 | 14 | 14 | 17.32 | 54.41 |
| 8 | P½ | 57 | 17 | 16 | 18.13 | 56.96 |
| 9 | R½ | 60 | 20 | 18 | 18.95 | 59.52 |
| 10 | T½ | 62 | 22 | 20 | 19.76 | 62.07 |
Need every size? See the complete US ring size chart with UK, EU, India and Japan conversions.
What Is My Ring Size? How to Know Your Ring Size
If you are asking "what is my ring size?", measure first, then read the result against the chart. Most adults fall between US 5 and US 11, but finger size varies widely, so treat any average as a starting point, not a rule.
Fingers change during the day, so measure at least twice, ideally when your hands are warm and at a normal temperature. If your knuckle is larger than the base of your finger, choose a size that slides over the knuckle with slight resistance and still stays put at the base. Our ring size guide covers how to figure out ring size when you are between sizes.
How to Check Ring Size Accurately: Practical Tips
- Calibrate carefully. The card step is the foundation of every measurement.
- Measure the right finger, since size differs between fingers.
- Allow for wide bands. A band wider than about 6 to 8 mm feels tighter, so go up a quarter to half a size.
- Repeat on a different day and use the middle value.
- Use the nearest half size. RingSize shows it under your US result.
- Confirm valuable rings with a jeweler.
Ring Size Guide: Sizing Up, Sizing Down and Ring Size Adjusters
If your result sits between two sizes, choose the larger one so the ring passes the knuckle comfortably. A slightly loose ring can be fixed: a jeweler can resize most metal rings by one or two sizes, and a ring size adjuster, such as a small spring coil or silicone sleeve, can make a ring fit a little tighter for a while. Some rings, including many tungsten, titanium and ceramic bands, cannot be resized at all, so measure properly before you buy. Our ring size adjuster guide explains the options.
Frequently Asked Questions About Ring Size
Is the RingSize ring size calculator free?
Yes. RingSize is free, runs in your browser and does not ask you to sign up. The measurements you make stay on your device.
How accurate is it?
Accuracy depends on careful calibration with a real card and on keeping the page at its normal zoom level. Treat the result as a reliable estimate and confirm the size with a jeweler for an expensive ring.
Why does RingSize only work on a phone?
Every screen has a different pixel density, so the tool needs a phone screen and a quick card calibration to turn pixels into millimetres. On a computer it shows a QR code so you can continue on your phone.
What if I do not have a ring to measure?
Use the paper strip method: wrap thin paper around your finger, mark the overlap and match its length on screen. Calibration also works with a ruler.
Which size system should I choose?
Pick the system your shop uses: US for the USA and Canada, UK for the UK and Australia, EU for most of Europe, IN for India and JP for Japan.
More answers: see all ring size FAQs.