Ring Size Finder — Measure a Ring on Your Screen
Place a ring that fits on the circle, adjust until it matches, and read your size in US, UK, EU, Japan and India sizes.
Place a ring on the circle and adjust until the circle fills the inside of the ring.
Not calibrated yet, so sizes may be off. Sizes are a guide; confirm with a jeweller before buying an expensive ring.
How the ring sizer works
Your ring size depends on the inside diameter of the ring. This tool draws a circle at real size on your screen. Lay a ring that already fits on the circle and adjust the circle until its edge lines up with the inside edge of the ring. The matching size appears in five sizing systems.
Related guides: How to Measure Your Ring Size at Home · How to Measure Your Wrist for a Bracelet or Watch
How to use it
- Tap Calibrate and match a bank card first. Without calibration the circle is not real size.
- Place a ring that fits well flat on the circle.
- Use − and + or the slider until the circle's outline sits just inside the ring's inner edge, then read your size.
Good to know
- EU sizes equal the inside circumference in millimeters (ISO 8653).
- Each whole US size adds about 0.81 mm to the inside diameter.
- Wide bands fit tighter; many jewellers suggest going up half a size for bands wider than about 6 mm.
- Already measured in mm, cm or inches? Use the mm to ring size converter.
Ring size chart
| US | Diameter (mm) | Circumference (mm) | UK | EU | Japan | India |
|---|---|---|---|---|---|---|
| 3 | 14.1 | 44.2 | F | 44 | 4 | 4 |
| 3½ | 14.5 | 45.5 | G | 45 | 5 | 5 |
| 4 | 14.9 | 46.8 | H | 47 | 7 | 7 |
| 4½ | 15.3 | 48.0 | I | 48 | 8 | 8 |
| 5 | 15.7 | 49.3 | J½ | 49 | 9 | 9 |
| 5½ | 16.1 | 50.6 | K½ | 51 | 10 | 10 |
| 6 | 16.5 | 51.9 | L½ | 52 | 12 | 12 |
| 6½ | 16.9 | 53.1 | M½ | 53 | 13 | 13 |
| 7 | 17.3 | 54.4 | N½ | 54 | 14 | 14 |
| 7½ | 17.7 | 55.7 | O½ | 56 | 15 | 15 |
| 8 | 18.1 | 57.0 | P½ | 57 | 16 | 16 |
| 8½ | 18.5 | 58.2 | Q¼ | 58 | 18 | 18 |
| 9 | 18.9 | 59.5 | R½ | 60 | 19 | 19 |
| 9½ | 19.4 | 60.8 | S½ | 61 | 20 | 20 |
| 10 | 19.8 | 62.1 | T½ | 62 | 21 | 21 |
| 10½ | 20.2 | 63.3 | U½ | 63 | 22 | 22 |
| 11 | 20.6 | 64.6 | V½ | 65 | 24 | 24 |
| 11½ | 21.0 | 65.9 | W½ | 66 | 25 | 25 |
| 12 | 21.4 | 67.2 | X½ | 67 | 26 | 26 |
| 12½ | 21.8 | 68.5 | Y½ | 68 | 27 | 27 |
| 13 | 22.2 | 69.7 | Z½ | 70 | 29 | 29 |
Three ways to calibrate
Auto-detect your device
The ruler recognizes about 130 phones, tablets, laptops and monitors, including iPhones, Galaxy phones, Pixels and MacBooks.
Enter your screen size
Enter your screen's diagonal size (for example, 15.6" for a laptop), and the ruler works out the scale from your screen resolution.
Calibrate with a bank card
Hold any bank card against the outline on screen and move the slider until they match. Bank cards are the same size everywhere: 85.60 × 53.98 mm.
How accurate is the ruler?
How accurate the ruler is depends on how well it knows your screen's pixel density, meaning how many pixels fit in an inch. There are three ways to set it, from most to least accurate:
Bank card (±0.5%): Bank and credit cards are made to one worldwide size, 85.60 × 53.98 mm (ISO/IEC 7810 ID-1). Because every card is exactly the same, matching one on screen gives the most accurate result.
Auto-detect (±1%): The ruler looks up your device's published screen size and resolution. Screens of the same model can differ very slightly, so this is a little less exact. It covers about 130 devices.
Screen size (±2%): You type in your screen size, and the ruler works out the rest from your resolution. Advertised sizes are rounded (a "15.6-inch" screen may really be 15.59 inches), so this is the least exact method. It's a good fallback when you don't have a card.
Real-life objects to check your measurements
Use these everyday objects to confirm the ruler is calibrated correctly.
Bank or credit card: 85.60 × 53.98 mm (3.37 × 2.13 in)
A4 paper: 210 × 297 mm (8.27 × 11.69 in)
US Letter paper: 8.5 × 11 in (215.9 × 279.4 mm)
US quarter: 24.26 mm (0.955 in) across
1 euro coin: 23.25 mm (0.915 in) across
AA battery: about 50.5 mm long and 14.5 mm wide