- For the most reliable result, ask a jeweller to use a finger gauge set.
- For an existing round ring, measure the inner diameter across the widest internal point.
- Do not include the metal thickness. Record millimetres to one decimal place when possible.
- The mathematical circumference is diameter × π, but home measurement error can exceed the rounding difference.
- Measure when fingers are at a normal temperature and avoid forcing a narrow gauge over a swollen joint.
Reference basis
This page describes a measurement procedure. It does not certify the fit of a specific product.