Choose a ring that already fits the same finger and hand, check that its interior is round, and have a jeweler read it on a mandrel when possible. A photo, screen comparison, distorted ring, or ring from another finger cannot support a precise size.

Use a well-fitting ring as a physical reference only when it belongs to the intended finger, remains round, and can be checked at its true inside center.

What this guide covers

Choose a suitable reference ring
Check its shape before measuring
Measure the true inside center
Confirm the reading on a mandrel

A reference ring has to be comparable

Before you measure
This method estimates size from a ring that already fits. It is not dependable when the ring belongs to another finger or wearer, has a very different band shape, or is visibly oval, bent, or irregular inside.

Is this ring a useful reference?

Use the ring only when every answer below is clear.

It fits the same finger and hand intended for the new ring
It sits comfortably rather than being a ring that is already too tight or loose
Its inside edge is round, not oval, bent, or visibly distorted
Its band style is reasonably comparable to the intended ring
It can be measured physically rather than from a photo or screen

Measure the existing ring

Keep the ring level and measure the open interior—not the outside metal.

Step 1 — Confirm where it is normally worn
Write down the exact finger and hand before taking any number. A ring that fits elsewhere is not a substitute.
Step 2 — Inspect the circle
Place the ring on a flat surface and look for an even, round interior. Stop if it appears bent or oval.
Step 3 — Measure the inside center
Read from one inside edge to the opposite inside edge across the widest true center. Keep the unit in millimeters and do not include the band metal.
Step 4 — Ask for a mandrel check
A jeweler can place the ring on a ring mandrel and account for its width and profile before a final size is chosen.

When not to convert the measurement

The ring is distorted

A single diameter from an oval or bent interior can create false precision. Have the ring inspected instead.

The wearing context is unknown

If you do not know which finger and hand it fits, preserve the uncertainty rather than assigning a final size.

Only a photo is available

Screen scale, camera angle, and perspective are not controlled. Ask for a physical ring or a new finger measurement.

Existing-ring measurement questions

Do I measure the outside or inside of the ring?

Measure the open interior across its true center. The outside diameter includes the band metal and does not represent the finger opening.

Can I use a ring from the other hand?

Not as an exact match. Use a ring worn on the same finger and hand, or measure the intended finger directly.

What if the ring is slightly oval?

Do not convert one diameter into a precise size. A jeweler should inspect and measure it with an appropriate physical tool.

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