Step 1 · Calibrate
Hold any bank or credit card flat against the box and slide until the box edges line up exactly with your card. This sets your screen to true size.

Step 2 · Match your ring
Lay a ring you already wear over the circle and slide until the circle fills the inside of the band.

Prefer a ruler? Measure straight across the inside of the band and type it here — no calibration needed.

Step 1
Wrap a thin strip of paper — or our printed sizer — around the knuckle of your finger, the widest point a ring must pass over.

Step 2
Mark where the strip overlaps, lay it flat, and measure to that mark with a ruler.

Step 3
Enter that length below — your knuckle circumference.

Print this strip at 100% scale (turn off "fit to page"). Cut it out, make a small slot at the arrow, wrap it around your knuckle, and read your size where the strip passes through.

Preview only — the downloadable PDF is drawn to exact millimeter scale.