Ring Size by Existing Ring Tool
Enter the inner diameter of a ring that already fits well and convert that measurement into US, EU, and VN size references. This tool belongs to the Size & Measurement category and is the fastest option when you already have a ring in hand.
If you do not have an existing ring, start instead with the Ring Size by Paper Strip Tool. If you want a broader input method that also accepts circumference, compare the result with the Ring Size Calculator. If the shop lists a different market chart, finish inside the Ring Size Converter before returning to the bracelet designer.
Ring Size by Existing Ring Tool
Measure the inside diameter of a ring you already wear, enter that inner diameter here, and convert it into the closest US, EU, and VN ring size references.
Where to measure
Measure from inner edge to inner edge only. The red line shows the correct inside diameter.
Ring Diameter
17.30 mm
Converted
US 7 / O / Ni 17.3
Drag to adjust
17.3 mm
Tip: place the ring flat on a ruler and measure the widest inner line, edge to edge, ignoring the outer metal.
Mode
Inner diameter
Measured
17.3 mm
Converted ring
7 / O / Ni 17.3
Step 1
Place the ring on a ruler and measure the widest inner line, edge to edge.
Step 2
Ignore the outer metal thickness and record only the inside diameter.
Step 3
Use millimeters when possible because ring charts are more accurate at that scale.
US Size
7
UK Size
O
EU Size
54
JP Size
14
VN Size
Ni 17.3
Estimated Diameter
17.3 mm
Estimated Circumference
54.3 mm
This diameter is very close to a standard chart row, so the match should feel straightforward for most common ring styles.
Nearby options: down to US 6.5 or up to US 7.5.
Reference Chart
Common US, UK, EU, JP, and VN ring size chart
US American | UK British | Diameter (mm) Inner | EU European | JP Japanese | VN Vietnamese |
|---|---|---|---|---|---|
| 3 | F 1/2 | 14.1 | 44 | — | Ni 14.1 |
| 3.5 | G | 14.5 | 46 | 5 | Ni 14.5 |
| 4 | H 1/2 | 14.9 | 47 | 7 | Ni 14.9 |
| 4.5 | J | 15.3 | 48 | 8 | Ni 15.3 |
| 5 | K | 15.7 | 49 | 9 | Ni 15.7 |
| 5.5 | L | 16.1 | 51 | 11 | Ni 16.1 |
| 6 | M | 16.5 | 52 | 12 | Ni 16.5 |
| 6.5 | N | 16.9 | 53 | 13 | Ni 16.9 |
| 7 | O | 17.3 | 54 | 14 | Ni 17.3 |
| 7.5 | P | 17.7 | 56 | 15 | Ni 17.7 |
| 8 | Q | 18.2 | 57 | 17 | Ni 18.2 |
| 8.5 | R | 18.6 | 58 | 18 | Ni 18.6 |
| 9 | S | 19.0 | 60 | 19 | Ni 19.0 |
| 9.5 | T | 19.4 | 61 | 20 | Ni 19.4 |
| 10 | U | 19.8 | 62 | 21 | Ni 19.8 |
| 10.5 | V | 20.2 | 63 | 23 | Ni 20.2 |
| 11 | W | 20.6 | 65 | 24 | Ni 20.6 |
| 11.5 | X | 21.0 | 66 | 25 | Ni 21.0 |
| 12 | Y | 21.4 | 67 | 27 | Ni 21.4 |
| 12.5 | Z | 21.8 | 68 | 28 | Ni 21.8 |
| 13 | Z+1 | 22.2 | 70 | 29 | Ni 22.2 |
Related ring tools
Need to size without an existing ring?
Related conversion tools
Need more than a diameter-only route?
How existing ring diameter becomes a standard size
Every standard ring size chart links an inner diameter to a matching inner circumference and a market size label. Once you measure the inside diameter of a real ring, the tool compares that number against the closest row in the standard chart.
This approach is especially useful for gift planning because it starts from a ring the wearer already uses. You avoid guessing directly from finger width and move straight into a size reference that can be checked against common US, EU, and VN systems.
For the cleanest result, measure with a ruler that shows millimeters, place the ring flat on a bright surface, and read only the inner line. If you are still uncertain, compare the result with the Ring Size Calculator or size from scratch with the paper strip method.
Slim stack ring
Existing ring inner diameter 15.7 mm
US 5 · EU 49 · VN Ni 15.7
Classic daily ring
Existing ring inner diameter 17.3 mm
US 7 · EU 54 · VN Ni 17.3
Statement ring
Existing ring inner diameter 18.9 mm
US 9 · EU 60 · VN Ni 18.9
FAQ
Existing ring sizing questions
What part of the ring should I measure?
Measure the inner diameter only, from one inside edge straight across to the opposite inside edge. Do not include the outer metal thickness because that will make the size read too large.
Can I use this if the ring belongs to a different finger?
Only if that ring already fits the same finger you want to size. A ring that fits the middle finger, thumb, or opposite hand may not translate correctly to another finger.
What if my measurement falls between two standard sizes?
That usually means the ring sits between chart rows. For thin bands, the nearest size is often fine. For wider bands or fingers that swell during the day, the larger nearby size is usually safer.
Ring Size Calculator
Enter your ring diameter or finger circumference and instantly convert to US, EU, and VN ring size references.
Ring Size by Existing Ring Tool
Measure the inner diameter of a ring you already own and convert that inside diameter into US, EU, and VN ring sizes.
Ring Size by Paper Strip Tool
Wrap a paper strip around the finger, measure the overlap, and auto-convert that length into US, EU, and VN ring sizes.
Ring Size Converter
Convert ring sizes between US, EU, and VN systems and see the matching diameter and circumference reference.
Bracelet Size Calculator
Measure your wrist and get a suggested bracelet size with snug, regular, and relaxed fit recommendations.
Bangle Size Calculator
Measure around your knuckles to estimate a rigid bangle size, inner diameter, and easiest entry fit for hard bangles.
Jewelry Fit Simulator (Basic)
Choose a basic ring, bracelet, bangle, or necklace size and preview how that size sits on a simple hand or neck model.
Necklace Length Guide Tool
Preview how standard necklace lengths fall on the neck and chest, then compare the closest style label and layering use.
Layered Necklace Spacing Tool
Preview spacing between two or three necklace lengths so layered chains stack cleanly without crowding the same neckline zone.
Birthstone Bracelet Ideas
Explore month-by-month birthstone bracelet inspiration before sizing and designing your final piece.