Buying a ring as a surprise, or just don't want a trip to the jeweller? You can get a solid estimate of ring size at home with things you already have.

Method 1: string or paper strip (most reliable at home)

  1. Wrap a thin strip of paper or a piece of string snugly around the base of the finger.
  2. Mark where it overlaps itself.
  3. Measure that length flat against a ruler — that's the finger's circumference in mm.
  4. Match the circumference (or divide by π ≈ 3.14 for the diameter) against a ring size chart.

This is the most reliable free-hand method, but it needs a ruler or measuring tape to read the final length — which is where a lot of people get stuck.

Method 2: measure an existing ring you already have

If you already own a ring that fits the same finger (or a similar-sized finger), measure its inner diameter — straight across the inside, not around the outside.

  1. Place the ring flat.
  2. Measure the inside edge to inside edge, through the centre.
  3. Compare that number (in mm) to a ring size chart.

Method 3: no ruler at all? Use your phone screen

If you don't have anything to measure with, a calibrated phone screen works as a stand-in ruler:

  1. Open a screen ruler tool and calibrate it with a credit card (a few seconds — the tool walks you through it).
  2. Switch to mm or cm.
  3. Lay the ring flat on the screen edge, or use the coordinate readout to line up the inner edges.
  4. Read off the inner diameter and match it to a size chart.

It's not lab-precise, but it's a genuinely useful backup when there's no ruler or measuring tape around — and calibrating with a card keeps it far more accurate than eyeballing it against an un-calibrated on-screen ruler.

A quick sanity check

Whatever method you use, measure twice and take the smaller, more consistent reading — fingers swell slightly with heat and time of day, so a mid-day, room-temperature measurement tends to be the most reliable baseline.

Need to measure something else instead? The same Screen Ruler works for any small object — just calibrate once and it's saved for next time.