Circles shown at exact physical inner diameter · US 3–13 · UK A–Z · EU 44–70
Step 1: Click “Print This Page” above. In the print dialog, set scale/zoom to 100% and disable “Fit to page” or “Shrink to fit”.
Step 2: After printing, place a credit card on the calibration bar below. It must be exactly 85.6 mm wide. If it doesn't match, adjust your printer scale and reprint.
Step 3: Hold an existing ring flat over the circles. The circle that fits just inside the ring's inner edge is your size.
Calibration — Credit Card Reference
CREDIT CARD SIZE
85.6 mm × 54.0 mm
Place your card here to verify print scale
The dashed box above must exactly match a standard credit or debit card.
Hold Your Ring Over Each Circle
Circles show inner diameter only. The ring itself is wider — the inside hole must match the circle, not the ring band.
If between sizes, choose the larger circle. Fingers swell in heat — measure in the evening for the most comfortable fit.
Source: ISO 8653 standard · airingsize.com