Interactive tool
Measure your ring size
Choose a method below. The screen sizer needs a bank card and a ring that fits; the typed calculator needs a measurement you already have.
Step 1 — Calibrate with a bank card
Step 1 of 2
Place a real bank card flat against the screen. Adjust the rectangle below until its edges line up with the card. The rectangle's height follows the card's proportions automatically, so matching the width also checks the height.
If the rectangle is wider than your screen, rotate to landscape or use a larger screen — do not guess the card's width.
No size is shown until you confirm calibration. Skipping calibration would produce a fabricated result, so the tool refuses to guess.
Step 2 — Match the circle to the ring's inner edge
Step 2 of 2
Diameter and circumference appear here once calibration is confirmed.
Enter a diameter in millimetres, then Apply. It must be inside the chart range (12–24 mm).
Before you start
Measure in the evening
Hands are warm and at their largest in the evening. Avoid measuring straight after exercise or in a cold room.
Measure the right finger
Finger sizes differ between hands and fingers. Measure the exact finger the ring will be worn on.
Repeat and take the largest
Measure two or three times. If readings differ, use the largest — a ring must clear the knuckle to be worn.
Why you can trust this result
- Calibration uses a standard bank card (85.6 mm wide, ISO/IEC 7810 ID-1) — a physical reference, not a guess about your screen.
- Your measurement is calculated in your browser and is not sent to a server. There is no account, and analytics runs only if you consent to it.
- Results are guidance, not a guarantee. For an expensive or hard-to-resize ring, confirm with a professional fitting.
Related guides
- Measure at home guide
Paper strip and existing-ring methods, step by step.
- International ring size chart
Look up any size by diameter or circumference.