How to find your ring size at home, and how the size systems compare
A ring that is too tight is uncomfortable; one that is too loose may slip off and be lost. Buying online or choosing a surprise gift makes the question even trickier. The good news: you can get a reliable estimate of a ring size at home with very little equipment. Here is how, along with an explanation of the different size systems you will meet.
The two measurements that matter
A ring size is based on the inside of the ring, expressed either as:
- its inside diameter, in millimetres;
- or its inside circumference, in millimetres.
Different countries then translate these measurements into their own scales, which is why the same ring can be called size N in London, size 7 in New York and size 54 in Paris.
Method 1: measure a ring that already fits
This is the most reliable home method.
- Choose a ring that fits the intended finger comfortably.
- Place it flat on a ruler and measure the inside diameter, from inner edge to inner edge, at the widest point.
- Measure twice, in two directions, to check the ring is round.
- Use the diameter to find the size in a conversion table.
Many jewellers also offer printable ring-size charts: you place the ring over circles until one matches the inside edge exactly. Check that the printout is at actual size by measuring the reference scale on the page.
Method 2: measure the finger
- Wrap a thin strip of paper or a piece of non-stretch string around the base of the finger.
- Mark the point where it overlaps, without pulling tight.
- Lay it flat and measure the length in millimetres: this is the circumference.
- Make sure the ring will pass over the knuckle: if your knuckle is larger than the base of your finger, measure both and choose a size between them.
This method is less precise than measuring a ring, because paper and string can stretch or slip. Repeat it two or three times.
Mistakes to avoid
- Measuring when your hands are cold. Fingers shrink in the cold and swell in heat. Measure at room temperature, ideally in the afternoon or evening.
- Measuring the wrong hand. Dominant-hand fingers are often slightly larger.
- Forgetting the band width. Wide bands fit more snugly than thin ones; for a band wider than about 6 mm, many jewellers suggest going up half a size or so.
- Using stretchy material. Elastic thread or fabric tape gives misleading results.
Comparing the size systems
The table below gives approximate equivalents for common sizes. Conversions vary slightly between charts, so always check the specific chart used by the retailer.
| Inside diameter (mm) | Inside circumference (mm) | UK & Australia | US & Canada | France (circumference) |
|---|---|---|---|---|
| 15.7 | 49.3 | J½ | 5 | 49 |
| 16.5 | 51.9 | L½ | 6 | 52 |
| 17.3 | 54.4 | N½ | 7 | 54 |
| 18.1 | 57.0 | P½ | 8 | 57 |
| 19.0 | 59.5 | R½ | 9 | 59.5 |
| 19.8 | 62.1 | T½ | 10 | 62 |
UK letters
The United Kingdom, Ireland and Australia use letters, from A upwards, with half sizes in between. Each letter corresponds to a small step in circumference.
US numbers
The United States and Canada use numbers, usually in quarter or half steps. Each full size corresponds to an increase of roughly 0.8 mm in diameter.
French and European circumference sizes
France and several European countries express ring sizes as the inside circumference in millimetres. A size 54 ring has an inside circumference of about 54 mm. This makes the French system the easiest to measure yourself: the number on your paper strip is, roughly, your size.
Finding the size for a surprise gift
- Borrow a ring the person wears on the right finger, measure it and put it back.
- Ask a close friend or relative who may know.
- Trace the inside of a ring on paper as a last resort.
- Choose an adjustable or open design, or a piece that does not depend on size, such as a pendant or earrings; our guides to bracelet designs and earrings offer ideas.
- Check the resizing policy before buying.
Can a ring be resized?
Often, yes. A jeweller can usually make a plain gold or silver band larger or smaller by a few sizes. Resizing is more difficult or impossible for:
- eternity rings set with stones all the way round;
- rings with engraving or patterns running round the whole band;
- some alternative metals, such as tungsten or titanium;
- thin, plated rings, where the plating would be damaged.
For an engagement ring, see our guide to choosing an engagement ring, which also covers metal and setting.
When to see a jeweller
For an important purchase, nothing beats a professional measurement with a set of sizing rings, which reproduces the real feel of a band, including passing over the knuckle. Most jewellers will do this free of charge.
In short
Measure a ring that already fits, or measure your finger carefully at room temperature, then convert using the retailer’s own chart. Remember that UK sizes use letters, US sizes use numbers and French sizes use the circumference in millimetres. When in doubt, a quick visit to a jeweller settles the question.
