Free Online Ring Size Gauge — Find Your Ring Size with a Coin
Don't know your ring size? Already own a ring but forgot the size? This tool uses a coin to calibrate your screen, then displays a real-size ring gauge so you can measure in seconds — no app needed.
STEP 1: Calibrate with a Coin
Place a US quarter (diameter: 24.26 mm) on the circle below and drag the slider until the circle matches the coin exactly.
No quarter? Use any coin whose diameter you know (e.g. penny = 19.05 mm, dime = 17.91 mm, nickel = 21.21 mm).
Current size: 200 px
How It Works
A US quarter (24.26 mm diameter) works best. Any coin with a known size will do.
Drag the slider until the on-screen circle exactly matches your coin, then tap "Confirm Size."
Place a ring on screen and drag the gold circle to fit inside the ring's inner edge. Your US ring size appears instantly.
US Ring Size Chart
| US Size | Inner Diameter (mm) | Inner Circumference (mm) |
|---|---|---|
| 3 | 14.1 | 44.2 |
| 4 | 14.9 | 46.8 |
| 5 | 15.7 | 49.3 |
| 6 | 16.5 | 51.9 |
| 7 | 17.3 | 54.4 |
| 8 | 18.1 | 56.9 |
| 9 | 19.0 | 59.5 |
| 10 | 19.8 | 62.1 |
| 11 | 20.6 | 64.6 |
| 12 | 21.4 | 67.2 |
Based on standard US ring sizing (diameter in mm).
Why This Tool Is Accurate
- No app needed: Works entirely in your browser — Safari, Chrome, or any mobile browser.
- Coin calibration: Physical coin size corrects for each phone's screen density, so results are accurate regardless of your model.
- Works on any phone: iPhone, Samsung Galaxy, Pixel, and more.
- Measure at room temperature: Fingers are slightly larger in warmth and smaller in cold. Measure when comfortable.
- Try at different times of day: Fingers can swell throughout the day. Measure at the end of the day for the most comfortable fit.
- Wide bands fit tighter: If the ring is a wide band (more than ~6 mm), go up a half size.
- Knuckle matters: If your knuckle is wider than your finger base, size to the knuckle.
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