6 accurate measuring methods, step-by-step instructions, tools you need, common mistakes to avoid, full AU/US/UK/EU size chart and a free ring size calculator.
1. Always measure the same finger and same hand the ring will be worn on โ sizes vary between fingers and hands. 2. Always measure in millimetres (mm) โ not centimetres or inches. 3. If between two sizes, always choose the larger size โ a ring that is too large can be resized down; one that is too small cannot be worn.
The single most important tool. Must have millimetre (mm) markings โ centimetre-only rulers are not precise enough for ring sizing.
โ EssentialCut to approximately 1 cm wide and 10 cm long. Used to wrap around the finger or inside an existing ring for circumference measurement.
โ EssentialUsed to mark the overlap point on the paper strip or string. A fine tip gives the most accurate mark โ avoid thick markers.
โ EssentialNon-stretchy thread works well as an alternative to paper. Dental floss is ideal โ it's thin, non-stretch, and available everywhere.
โก AlternativeThe most precise tool for measuring the inner diameter of an existing ring. Accurate to 0.1 mm. Available at hardware stores for under $15.
โก Best for accuracyPrint a ring size chart at exactly 100% scale. Place an existing ring over the printed circles to match the size without any measurement.
โก Handy alternativeApps like "Ring Sizer" can estimate size from a photo of a ring placed on a flat surface. Useful quick reference โ always verify with a ruler.
โก Quick estimateThe most accurate starting point for gift ring sizing. Borrow a ring worn on the intended finger. Even 30 seconds is enough to measure it.
โ Best sourceMost accurate method โ uses a ring they already own on the same finger
Choose a ring they regularly wear on the same finger and same hand the new ring will go on. Even 1โ2 minutes is enough time to complete this measurement.
Lay the ring flat on a hard, well-lit surface. A white piece of paper underneath makes it easier to see clearly.
Place a ruler across the inside of the ring โ from inner edge to inner edge. This is the inner diameter. Read the measurement in millimetres. Do not measure the outside of the ring.
Write the diameter down immediately. Look it up in the Diameter (mm) column of the size chart below to find the AU, US, UK or EU ring size.
For maximum accuracy, use vernier calipers instead of a ruler. Calipers can measure to 0.1 mm precision, which can be the difference between a half size. Take your borrowed ring to a jeweller if you are unsure โ they will size it in under a minute for free.
Great alternative when you only have the ring for a few seconds
Lay the ring flat on a sheet of white paper. Keep the ring completely still โ use a small piece of blu-tack to hold it in position if needed.
Use a fine-tip pen to trace carefully around both the inner edge and the outer edge of the ring. Keep the pen vertical (not angled) for accuracy.
Use a ruler to measure straight across the traced inner circle โ from one side to the directly opposite side. Measure in mm. This is your inner diameter.
Find the matching diameter in the chart below or enter it into the calculator above to get the ring size in AU, US, UK and EU formats.
Take the traced paper to a jewellery store rather than measuring it yourself โ a professional can match it against their sizing mandrel for perfect accuracy. This is especially important for engagement rings.
Use when you can measure their finger directly (e.g. while they sleep)
Cut a strip approximately 8โ10 mm wide and 10 cm long. Non-stretch paper is essential โ elastic or stretchy materials give inaccurate results.
Wrap the paper strip snugly around the base of the finger where the ring will be worn. Make sure it passes comfortably over the knuckle without being forced.
Use a fine-tip pen to mark exactly where the paper strip overlaps itself. This mark represents the inner circumference of the finger.
Remove the strip, lay it flat on a hard surface, and measure from the end of the strip to the pen mark with a ruler. This measurement in mm is the finger circumference.
Find the matching value in the Circumference (mm) column of the size chart below, or enter it directly into the calculator using the "Circumference (mm)" option.
If the measurement falls between two sizes, always choose the larger one for a gift. Also check whether the strip passed easily over the knuckle โ if the knuckle is noticeably larger than the base, add half a size to your result.
Same principle as paper strip โ use thread or dental floss instead
Use dental floss, embroidery thread, or thin twine. Do not use elastic thread, wool, or any material that stretches โ this gives a false reading that is too small.
Wrap once around the base of the target finger. The thread should sit snugly โ not tight, not loose. It should be able to slide over the knuckle with light pressure.
Hold or mark the overlap point, then lay the thread flat and measure the length from end to mark in mm. This is the circumference.
Use the Circumference (mm) column in the chart below or the calculator to find the matching AU ring size.
The string method is slightly less accurate than paper because strings can twist or compress. For higher accuracy, repeat 3 times and take the average of the three measurements before converting to a ring size.
For when you have the ring for only a moment and need a quick capture
Bar soap works best when slightly moist. Modelling clay (like Blu-tack or craft clay) is an excellent alternative and can be reused multiple times.
Press the ring flat and evenly into the soap or clay to create a clean circular impression. Do not press too hard โ you want a shallow, clean circle, not a deep deformation.
Once the ring is removed, measure straight across the inner circle of the impression in mm. This is the inner diameter of the ring.
Use the Diameter (mm) option in the calculator below or find the matching row in the size chart.
The impression method can be slightly distorted if the ring is not pressed perfectly flat. Always press straight down โ not at an angle โ and measure across the widest part of the impression circle for accuracy.
No ruler needed โ just print, place and match
Search for "printable ring sizer PDF" from Blue Nile, Brilliant Earth, or Michael Hill. When printing, set scaling to 100% (Actual Size) โ never "Fit to Page." Check the printed reference line matches the stated mm length exactly.
Take one of their existing rings and place it over the printed circles on the chart, one at a time.
The circle where the inner edge of the ring lines up perfectly with the outer edge of the printed circle is your size match.
The size is usually printed inside or next to the matching circle. Cross-reference with the conversion chart below to find the AU equivalent if needed.
Always verify the print scale is correct by measuring the printed reference bar with a physical ruler. Even 1 mm of scale error can result in the wrong ring size. When in doubt, take the printed chart and the borrowed ring to a jeweller for confirmation.
Best overall method โ fast and reliable
Most precise โ 0.1 mm accuracy
Very good when pen is held vertically
Accurate only if printed at 100% scale
Good โ higher in warm conditions
Can be affected by string tension
Good backup when you have seconds
Useful quick estimate โ verify with ruler
Last resort only โ high chance of error
| AU / UK | US / Canada | EU / ISO | Diameter (mm) | Circumference (mm) | Typical Wearer |
|---|---|---|---|---|---|
| F | 3 | 44 | 14.07 mm | 44.2 mm | Child / Petite |
| G | 3ยฝ | 45.5 | 14.48 mm | 45.5 mm | Small Women |
| H | 4 | 46.75 | 14.88 mm | 46.8 mm | Women |
| I | 4ยฝ | 48 | 15.29 mm | 48.0 mm | Women |
| J | 4ยพ | 48.75 | 15.49 mm | 48.7 mm | Women |
| K | 5ยผ | 50 | 15.90 mm | 50.0 mm | Women |
| L | 5ยพ | 51.25 | 16.31 mm | 51.2 mm | Women |
| M | 6ยผ | 52.5 | 16.71 mm | 52.5 mm | Safe Gift โ |
| N โญ | 6ยพ | 53.75 | 17.12 mm | 53.8 mm | Most Common โ |
| O | 7ยผ | 55 | 17.52 mm | 55.1 mm | Women |
| P | 7ยพ | 56.25 | 17.93 mm | 56.3 mm | Men / Large โ |
| Q | 8ยผ | 57.5 | 18.34 mm | 57.6 mm | Men |
| R | 8ยพ | 59 | 18.75 mm | 58.9 mm | Men |
| S | 9ยผ | 60.25 | 19.15 mm | 60.2 mm | Safe Gift โ |
| T โญ | 9ยพ | 61.5 | 19.56 mm | 61.4 mm | Most Common โ |
| U | 10ยผ | 62.75 | 19.96 mm | 62.7 mm | Popular โ |
| V | 10ยพ | 63.75 | 20.27 mm | 63.7 mm | Men |
| W | 11 | 64.5 | 20.68 mm | 64.9 mm | Men |
| Z | 12ยฝ | 68.5 | 22.00 mm | 68.5 mm | XL |
Proportional circles for popular sizes. For reference only โ always confirm with a ruler in mm.
Always measure the inner diameter โ the space inside the ring that sits against the finger. The outer diameter includes the metal band thickness and will give a size 2โ4 sizes too large.
โ Fix: measure inside, not outsideRing sizes differ between fingers on the same hand. Borrowing a pinky ring to size a ring-finger gift will result in a significantly too-small size. Always use a ring from the exact intended finger.
โ Fix: match finger and hand exactlyElastic thread, wool, or stretchy ribbon gives a false reading that is too small โ the material compresses around the finger. Always use paper, dental floss, or non-stretch thread.
โ Fix: use paper strip or dental flossIf a printable ring sizer is printed at "Fit to Page" or any scale other than 100%, all the circles will be the wrong size and every match will be incorrect. Always print at 100% actual size.
โ Fix: verify with ruler before useCold fingers can be up to a full size smaller than warm fingers. A measurement taken on a cold winter day may result in a ring that is too tight during summer or after physical activity.
โ Fix: measure when hands are warmWhen a measurement falls between two ring sizes, some people instinctively choose the smaller to avoid a loose fit. Always choose the larger size for a gift โ resizing down is easier and cheaper than enlarging.
โ Fix: always go one size up