The paper strip
- Cut a thin strip of paper, about 80mm long and 5mm wide.
- Wrap it around the base of the finger the ring will live on. Snug, not tight.
- Mark the point where the strip meets itself.
- Lay it flat. Measure from the start to the mark in millimetres.
- That number is your circumference — divide by 3.14 for your inner diameter, then read it against the chart below.