Ring Sizer: Ring Size Measure

Find your ring size at home in a minute — and get it right.

Ring Sizer measures a ring or a finger right on your phone screen. Unlike other ring size apps, it first calibrates the screen with a bank card or a coin — objects of a known exact size — so the on-screen circle matches real millimetres on your particular device. No guessing, no "it came two sizes off".

HOW IT WORKS
1. Calibrate once. Put a bank card (85.6 × 54 mm, same on every card) or a coin from the built-in list on the screen and fit the frame to it.
2. Measure a ring. Place the ring on the screen and fit the circle to its inner edge. Two guide lines make it unambiguous: the red one must hide under the ring, the green one must stay visible right against the inner edge.
3. Read your size in every system at once: US / Canada, UK / Australia / NZ / Ireland / South Africa, EU (ISO 8653), Italy / Spain / Netherlands / Switzerland, Japan, China / Hong Kong, India — plus inner diameter and circumference in mm for your jeweller.

NO RING? MEASURE YOUR FINGER
Wrap a strip of paper or a thread around the base of your finger, mark the overlap and lay it along the calibrated on-screen ruler. Enter the length and Ring Sizer converts the circumference to your ring size.

RING SIZE CHART AND CONVERTER
A complete ring size chart with US half sizes, UK letters, EU, Italian, Japanese, Chinese and Indian sizes side by side, with diameter and circumference in mm. The converter turns any size into any other — mm to ring size, US to EU, UK to US — fully offline.

SAVE AND SHARE
Keep sizes for yourself and for the people you buy for: "Me", "Mom", "Anna — surprise". Share a size as text in one tap — handy when ordering an engagement ring or a gift online.

WHY RING SIZER
• Calibrated accuracy: measures real millimetres, not pixels. Accurate to about 0.2 mm.
• Measure ring size at home — no printable ring sizer, no trip to the shop.
• Works with any ring: wedding band, engagement ring, signet, rings with a stone (move the circle to the screen edge so the setting hangs off).
• All ring size systems in one place, with a full ring size chart.
• No account, no camera, no tracking. Works offline.
• No ads. The app is free; if it helped, you can thank the developer with a one-time purchase.

TIPS FOR AN ACCURATE RING SIZE
• Fit the circle to the INNER edge of the ring.
• Look at the edge with one eye, straight from above: the pixels lie under the glass, and a slanted view shifts the line.
• Measure 2–3 times and take the larger result if they land on neighbouring sizes — the ring has to pass over the knuckle.
• Measure fingers in the evening at room temperature, not when they are cold.

What is my ring size? Open Ring Sizer, calibrate with a card or a coin, and find out.