Complete step-by-step UK guide to measuring ring size using a ruler โ measure an existing ring's inner diameter OR measure your finger circumference with paper/string and a ruler. Full UK ring size chart AโZ+2 in mm included for 2026
Method 1 (Existing Ring): Place a well-fitting ring on a flat surface. Lay your mm ruler across the inside of the ring and measure the inner diameter in mm. Example: 16.5 mm = UK M. Multiply by ฯ (3.14159) if you need the circumference.
Method 2 (Paper or String + Ruler): Wrap a paper strip or cotton string around the finger base, mark the overlap, lay flat and measure in mm with your ruler. That reading is the circumference โ look it up in the chart below.
Place a well-fitting ring flat on a hard surface. Lay a mm ruler across the inside of the ring. Measure the inner diameter from one inner edge to the opposite inner edge in mm. Look up in the Diam. (MM) column below. Fast and highly accurate.
Wrap a thin strip of plain paper around the finger base and mark the overlap. Lay flat and measure from end to mark in mm with the ruler. This gives your finger circumference โ look up in Circ. (MM) column below. The most popular free method.
Wrap non-stretchy cotton string or waxed dental floss around the finger base. Mark overlap. Straighten flat and measure to your mark in mm with the ruler. Works identically to the paper method โ use if no paper is available.
A digital calliper measures the inner ring diameter to ยฑ0.1 mm โ far more precise than a standard ruler alone. If you have access to digital callipers, use the inner jaw measurement on an existing ring for the best at-home accuracy available.
Place an existing ring on paper and trace around the inner circle with a pencil. Measure the traced circle's inner diameter in mm with a ruler. Less precise than measuring the ring directly, but useful when you want to keep the ring on the finger.
Any UK jeweller will size your ring for free using calibrated metal ring gauges. This is the most accurate method of all and is recommended for engagement rings, eternity bands, and any ring over ยฃ100 regardless of at-home method used.
Select a ring that currently fits comfortably on the exact finger and hand you plan to wear the new ring on. It should slide on smoothly and sit snugly without being tight. If no ring fits perfectly, use the paper strip or string method (Method 2) instead.
Lay the ring perfectly flat on a table, desk or book. A light-coloured hard surface is easiest to read against. Make sure the ring is not tilted or resting on its side โ it must lie flat to give an accurate diameter reading.
Place the ruler so it crosses through the centre of the ring opening. The ruler must pass through the very widest point of the inner circle โ not at an angle. Ensure the zero end of the ruler lines up exactly with the inner edge of the ring on one side.
Read the measurement in millimetres (mm) at the point where the ruler meets the opposite inner edge of the ring. This is the ring's inner diameter. Read to the nearest 0.5 mm for maximum accuracy. Example: 16.5 mm = UK M (women's most common).
Rotate the ring 90ยฐ and measure the diameter again in mm. The two readings should be identical if the ring is a perfect circle. If they differ by more than 0.5 mm, the ring may be slightly oval โ take the average of the two readings.
Find your diameter reading in the Diam. (MM) column of the UK ring size chart below. The UK letter size in the first column is your ring size. If your reading falls between two rows, always choose the larger UK letter size.
Use plain printer paper. The strip should be long enough to wrap around your finger with some overlap. A width of 5 mm is ideal โ narrow enough to wrap flat, wide enough to mark cleanly. Use non-stretchy paper only. Your mm ruler will be used in Step 5 to measure the strip.
Fingers are at their largest in the evening when warm. Cold fingers or morning measurements can read up to one full UK letter size smaller. Warm your hands under lukewarm water for 30 seconds if needed before measuring.
Wrap the strip around the base of the finger you will wear the ring on โ just above where it meets the palm. Snug but not tight: you should be able to slide it very slightly. If it leaves a red mark it is too tight.
With a fine-tip ballpoint pen, mark a precise thin line on the strip at the exact overlap point. A sharp mark gives the best ruler reading in the next step.
Remove the strip. Lay it flat on a hard surface. Place the zero end of your ruler at the very edge of the strip. Read the measurement in millimetres at your pen mark. This is your finger circumference in mm. Repeat 3 times and take the average.
Find your average mm reading in the Circ. (MM) column of the chart below. If your reading falls between two rows, always choose the larger UK letter size.
| UK Size | Diam. (MM) โ Ruler on Ring | Circ. (MM) โ Strip + Ruler | Circ. (CM) | ๐บ๐ธ US | ๐ช๐บ EU | Best For |
|---|---|---|---|---|---|---|
| F | 13.9 mm | 43.7 mm | 4.37 cm | 3 | 44 | XS Women |
| G | 14.3 mm | 44.9 mm | 4.49 cm | 3.5 | 45 | Small Women |
| H | 14.7 mm | 46.2 mm | 4.62 cm | 4 | 46 | Small Women |
| I | 15.0 mm | 47.1 mm | 4.71 cm | 4.5 | 47 | Small Women |
| J | 15.3 mm | 48.0 mm | 4.80 cm | 5 | 48 | Women |
| Jยฝ | 15.5 mm | 48.7 mm | 4.87 cm | 5.25 | 49 | Women |
| K | 15.7 mm | 49.3 mm | 4.93 cm | 5.5 | 49 | Women |
| Kยฝ | 15.9 mm | 49.9 mm | 4.99 cm | 5.75 | 50 | Women |
| L โญ | 16.1 mm | 50.6 mm | 5.06 cm | 6 | 51 | Women Popular |
| Lยฝ | 16.3 mm | 51.2 mm | 5.12 cm | 6.25 | 51 | Women Popular |
| M โญ | 16.5 mm | 51.9 mm | 5.19 cm | 6.5 | 52 | Most Common โญ |
| Mยฝ | 16.7 mm | 52.5 mm | 5.25 cm | 6.75 | 53 | Women Popular |
| N โญ | 16.9 mm | 53.1 mm | 5.31 cm | 7 | 53 | Most Common โญ |
| Nยฝ | 17.1 mm | 53.8 mm | 5.38 cm | 7.25 | 54 | Women |
| O | 17.3 mm | 54.4 mm | 5.44 cm | 7.5 | 54 | Unisex |
| Oยฝ | 17.5 mm | 55.0 mm | 5.50 cm | 7.75 | 55 | Unisex |
| P | 17.8 mm | 55.9 mm | 5.59 cm | 8 | 56 | Unisex |
| Q | 18.2 mm | 57.2 mm | 5.72 cm | 8.5 | 57 | Slim Men |
| R | 18.6 mm | 58.5 mm | 5.85 cm | 9 | 59 | Men |
| S | 19.0 mm | 59.7 mm | 5.97 cm | 9.5 | 60 | Men |
| T โญ | 19.56 mm | 61.4 mm | 6.14 cm | 10 | 61 | Men Most Common โญ |
| Tยฝ | 19.76 mm | 62.1 mm | 6.21 cm | 10.25 | 62 | Men Popular |
| U โญ | 19.96 mm | 62.7 mm | 6.27 cm | 10.5 | 63 | Men Popular |
| V โญ | 20.37 mm | 64.0 mm | 6.40 cm | 11 | 64 | Men Popular |
| W | 20.78 mm | 65.3 mm | 6.53 cm | 11.5 | 65 | Men |
| X | 21.18 mm | 66.6 mm | 6.66 cm | 12 | 67 | Large Men |
| Y | 21.59 mm | 67.8 mm | 6.78 cm | 12.5 | 68 | Large Men |
| Z | 21.99 mm | 69.1 mm | 6.91 cm | 13 | 69 | XL Men |
| Z+1 | 22.20 mm | 69.7 mm | 6.97 cm | 13.5 | 70 | XL / Custom |
| Z+2 | 23.01 mm | 72.3 mm | 7.23 cm | 14 | 72 | Custom |
1. Using the cm side instead of the mm side. UK ring half-sizes are only 0.6โ1.3 mm apart. Reading in cm gives only 1 mm precision at best โ always use the millimetre side of your ruler for ring sizing.
2. Not passing the ruler through the centre of the ring. The ruler must cross at the widest point of the inner opening to read the true inner diameter. An off-centre reading will be shorter and give a size that is too small.
3. Measuring the outer diameter instead of the inner diameter. Ring sizes are based on the inner diameter โ the part that touches your finger. The outer diameter includes the band thickness and will give a reading that is too large.
4. Measuring a ring worn on the wrong finger. Ring sizes differ between fingers and hands. Always measure the ring you wear specifically on the target finger on the target hand.
5. Measuring the paper strip without laying it perfectly flat. Any bow, curl or twist in the paper strip when read against the ruler will give a shorter reading. Always ensure the strip lies completely flat on a hard surface before reading.