Ring Sizing Tools Compared: Mandrels, Sizers and Printables
Which sizing tool to trust, from professional steel mandrels to plastic multisizers and printable paper charts.
5 min read
Not all sizing tools are equally reliable. Here is how they compare, from the professional standard down to the free options.
Steel mandrel and sizing rings
The jeweller's setup: a tapered steel mandrel marked with sizes, plus a set of steel rings on a keyring. You try the rings until one fits, and the mandrel is used to check and shape the finished band. This is the most accurate method available and it is free at any high street jeweller. The steel rings are the important half, because a mandrel measures a ring, not a finger.
Plastic multisizers
A single plastic strip with a buckle that tightens around the finger, marked with sizes on one edge. Inexpensive, reusable and surprisingly accurate — within about a quarter size — provided you do not overtighten. Many online jewellers post these free. The main limitation is that the flat plastic strip does not replicate the feel of a rigid band over the knuckle.
Plastic sizing ring sets
A set of individual plastic rings in each size. More accurate than a strip because each one is a rigid loop you actually pass over the knuckle. Cheap and the best home option.
Printable paper charts
A downloadable sheet with printed circles to match against an existing ring, or a strip to cut out and wrap. Free, but only correct if the page prints at exactly 100 per cent with no fit-to-page scaling. Always verify the printed test ruler against a real one before trusting the result, and re-check after any printer change.
String and paper
The improvised method described in most guides. Adequate when done carefully with non-stretch paper and a steel ruler, and it gives you the circumference directly. Its accuracy depends entirely on not pulling tight.
Digital callipers
Excellent for measuring an existing ring's inside diameter to a tenth of a millimetre. Not useful for measuring a finger. If you buy or sell rings regularly, a cheap pair pays for itself.
Which to choose
For a one-off purchase, borrow a jeweller's sizing rings. For online shopping, request a free plastic sizer. For measuring rings you already own, use callipers or a ruler and the converter. Whatever you use, record the result in millimetres — it is the only figure that stays valid across every tool and every country.