Actual Size Viewer & Ring Sizer
Rings, coins and everyday objects drawn at their real physical size on your screen. Calibrate once and what you see is what you get.
Actual size viewer
Calibrate before you rely on this. Until you do, everything below is drawn at the browser's assumed 96 DPI, which is wrong on most screens. A ring size read from an uncalibrated screen can easily be two sizes out.
Not calibrated
Place a ring you already own flat on the screen and move it over the circles until one matches the inside edge of your ring. That circle is your size.
Tap a circle to see its full conversions.
Ring size conversion chart
| US / Canada | UK / AU | ISO / EU | Inside ⌀ (mm) | Inside ⌀ (in) |
|---|---|---|---|---|
| 3 | F | 44.2 | 14.07 | 0.55 |
| 3.5 | n/a | 45.5 | 14.47 | 0.57 |
| 4 | H | 46.8 | 14.88 | 0.59 |
| 4.5 | n/a | 48.0 | 15.29 | 0.60 |
| 5 | J½ | 49.3 | 15.69 | 0.62 |
| 5.5 | n/a | 50.6 | 16.10 | 0.63 |
| 6 | L½ | 51.9 | 16.51 | 0.65 |
| 6.5 | n/a | 53.1 | 16.91 | 0.67 |
| 7 | N½ | 54.4 | 17.32 | 0.68 |
| 7.5 | n/a | 55.7 | 17.73 | 0.70 |
| 8 | P½ | 57.0 | 18.13 | 0.71 |
| 8.5 | n/a | 58.2 | 18.54 | 0.73 |
| 9 | R½ | 59.5 | 18.95 | 0.75 |
| 9.5 | n/a | 60.8 | 19.35 | 0.76 |
| 10 | T½ | 62.1 | 19.76 | 0.78 |
| 10.5 | n/a | 63.3 | 20.16 | 0.79 |
| 11 | V½ | 64.6 | 20.57 | 0.81 |
| 11.5 | n/a | 65.9 | 20.98 | 0.83 |
| 12 | X½ | 67.2 | 21.38 | 0.84 |
| 12.5 | n/a | 68.5 | 21.79 | 0.86 |
| 13 | Z½ | 69.7 | 22.20 | 0.87 |
ISO/EU sizes are the inside circumference in millimetres. UK letters are given for whole US sizes only, because the letter scale does not map cleanly onto US half sizes and interpolating it would mislead.
Each coin is drawn at its official diameter. Hold a real coin against one to confirm your calibration, or use them to judge the size of something in a photo.
US coins
Euro coins
Common objects at true size. Useful for checking a listing's stated dimensions, or as a sanity check on your calibration.
Finding your ring size without a jeweller
The most dependable way to size a ring at home is not to measure your finger. It is to measure a ring you already own and wear comfortably. Fingers change through the day and with temperature. A ring does not. Lay it flat on the screen, line its inside edge up against the circles above, and read off the size that matches.
Ring sizing is defined by the inside of the band, and the three main systems simply express that measurement differently. US and Canadian sizes run on a numeric scale where each whole size adds about 2.55 mm of inside circumference. UK and Australian sizes use letters. The ISO and continental European size is the most direct of the three, because it is the inside circumference in millimetres: an ISO 54 ring measures 54 mm around the inside. A US 7 is a UK N½ and an ISO 54.4, all describing one ring.
Two things catch people out. The first is band width. A wide band sits against more of your finger and feels tighter than a narrow one at the same nominal size, which is why jewellers often suggest going up a half size past roughly 6 mm of width. The second is that a knuckle can be larger than the base of the finger. The ring has to pass over it, so you size for the knuckle and accept that it may spin once on.
Why calibration is not optional here
An actual size ruler or ring sizer is only as good as its assumption about your screen. Browsers lay out in CSS pixels, defined as 1/96 of an inch, and real displays are nothing like that. A high-density laptop can exceed 160 pixels per inch. An uncalibrated ring sizer on such a screen draws every circle far too small, and reading a size two steps out and ordering a ring that will not fit is entirely possible.
So this page warns you plainly until you calibrate, rather than quietly showing figures it cannot stand behind. Calibration is one step: hold a bank card against the screen and match the outline. Every card worldwide is 85.6 mm wide under ISO/IEC 7810, which makes it a reference nearly everyone carries. Afterwards, hold a coin against its circle in the Coins tab. If it matches, your calibration is sound and every tool on the site is now accurate.
Coins and objects as a scale reference
The coin diameters here are official specifications from the issuing mints, which makes them useful in both directions: as a way to check your calibration, and as a familiar scale for judging how big something is. A US quarter is 24.26 mm across and a two-euro coin is 25.75 mm, close enough that seeing both at true size tells you more than either number does alone.
The everyday objects tab covers what people most often check against a listing: bank and business cards, AA and AAA batteries, SD and microSD cards. To measure something not listed, the ruler handles it directly, and the paper size guide covers standard sheet formats.