Ring Sizer: Size & Convert

Measure a ring right on your screen, calibrated to real size, and convert instantly between US, UK, EU, JP and KR standards.

Find a ring size without a physical gauge. Ring Sizer lets you place a ring you already own on the screen, match it to an on-screen circle, and read the size — then convert it to every standard used around the world.

Accuracy comes from calibration: the app uses your device's screen size, and you can fine-tune it once by matching a standard bank card, so the circle on screen is true to life.

▶ Measure a ring Place a ring on the screen, pinch or slide the circle to match its inside edge, and see the inner diameter in mm with US, UK, EU and JP sizes at once.

▶ Finger guide Use the on-screen band as a width guide, or enter a circumference you measured with string or paper for a more reliable result.

▶ Convert any standard Enter US, UK, EU, JP, inner diameter or circumference and get the full conversion, plus a complete size chart.

▶ Card calibration Auto-calibrate from your device, then confirm with a bank card outline for a true-to-size circle, shown by an accuracy badge.

▶ Save sizes Keep sizes for family and partners with name labels — perfect for gifts and surprise proposals.

On-screen results are estimates within about half a size and depend on calibration, so confirm at a jeweller before ordering. Finger width is not the same as circumference; the string method is more accurate. Works offline, no account needed.