📏 Free Interactive Tool

Online Ring Sizer

Find your perfect ring size instantly — no jeweler needed. Place your ring on screen, drag to match the inner edge, and get your US, UK, EU, and JP sizes in real time.

For best accuracy, calibrate using a standard credit card

Place your ring on the screen and adjust until it matches the inner edge.

Drag the purple handle at the top of the circle, or use the slider below, to resize. Calibrate with a credit card first for the most accurate result on your device.

⚙️ Screen Calibration

Place a credit card flat on screen. Drag the slider until the gold bar matches its full width (85.6 mm) exactly.
CREDIT CARD WIDTH — 85.6 mm (ISO Standard)
96 DPI
17.3 mm
12 mm (US ~1½)25 mm (US ~14)
Diameter—
Circ.—
US / CA—
UK / AU—
EU / DK—
Japan—

Estimates only. For a guaranteed fit, visit a professional jeweler with a ring mandrel.

How It Works

How to Use the Online Ring Sizer

1

Calibrate Your Screen

Place a credit card on screen. Drag the calibration slider until the gold bar exactly matches the card's full width (85.6 mm).

2

Place Your Ring

Lay a ring you already own face-down on your screen, centered over the purple circle. Use one that fits the correct finger.

3

Drag to Match

Drag the white handle at the top of the circle, or use the slider, until the purple ring aligns with your ring's inner edge.

4

Read Your Sizes

Your ring size in US, UK, EU, and JP formats — plus diameter and circumference — appears instantly in the panel below.

Pro Tips

Tips for the Most Accurate Reading

🌡️

Room Temperature Only

Fingers swell in heat. Measure when comfortable — not after a workout or hot shower.

🕑

Measure in the Afternoon

Fingers reach their natural full size in the afternoon. Morning readings can run up to half a size small.

💳

Always Calibrate First

Screen pixel density varies by device. Credit card calibration eliminates the most common source of sizing error.

💍

Use a Well-Fitting Ring

Choose a ring that fits the correct finger comfortably — not one that is even slightly loose or tight.

📏

Wide Bands Fit Tighter

Buying a band wider than 6 mm? Size up half a size — wider rings grip more of the finger and feel snugger.

🔁

Measure Multiple Times

Take 2–3 readings and average them. Minor positioning differences can affect results slightly.

Prefer a measurement-only approach? Use our ring size calculator — just enter your diameter or circumference in mm for an instant result, no screen calibration needed. Or browse the complete ring size circumference chart with all US, UK, EU, and JP sizes.
FAQ

Ring Sizer FAQs

When properly calibrated using the credit card method, the tool is accurate to within 0.5–1 mm — sufficient for standard ring sizing. The most common source of error is an uncalibrated screen. For a guaranteed fit, follow up with a professional jeweler using a physical ring mandrel.
Place a standard credit card flat on your screen — all standard credit cards are exactly 85.6 mm wide (ISO/IEC 7810 ID-1 format). Drag the calibration slider until the gold bar on screen matches the card's full width from edge to edge. Your screen is then correctly calibrated for real-world measurements.
Yes — the tool is fully touch-compatible. Drag the purple handle with your finger to resize, or drag the circle body to reposition it. Mobile screens have much higher DPI (300–500) than desktop monitors (96–144), so credit card calibration is especially important on phones.
Wrap a thin strip of paper snugly around your finger, mark where it meets, measure the length in mm, and match it to the circumference shown in the readout panel. Alternatively, use our ring size calculator. For more background, see the Wikipedia article on ring sizing.

Need a Different Sizing Method?

Use our calculator to convert any diameter or circumference in mm directly to international sizes — no screen calibration required.

🧮 Ring Size Calculator 📊 Full Size Chart