Find your ring size — accurately or secretly
Free tool for finding your ring size with three approaches: direct finger measurement, detective methods for secretly estimating someone else's size, and AR camera try-on. Every result converts automatically across US, UK, EU, JP, RU, CN, IN and AU sizing systems.
How to Find Your Ring Size
Match the on-screen card to a real credit card so every measurement is accurate to a fraction of a millimetre.
Choose Direct if you can measure your own finger, Detective to estimate someone else's size, or AR to try a virtual ring on camera.
Follow the on-screen guide: wrap a string, match a circle, or trace a ring. The result updates instantly.
The card shows your size in every country's system plus a honest confidence range so you know how sure to be before buying.
Measure, estimate or try rings on virtually — every country supported
Screen calibration Calibration saved How do I calibrate? ▾
Match the card width to a real card on your screen so measurements are accurate.
Drag the slider until the image matches the size of the real object on your screen.
Direct
Choose a method
Measure the length of the paper where it just meets itself (not overlapping).
Drag the slider until the circle exactly matches the inside of your ring.
Lay your finger across the circle at the place you'd wear the ring. Drag to match the width.
This PDF has a calibration square — print at 100% (no scaling).
Your result
🌡️ Swelling factors
Fingers swell up to half a size larger depending on time, temperature and diet. Tell us when you're measuring for a smarter result.
📐 Ring width
Wider rings need a larger size to slide over the knuckle comfortably.
💑 Couples mode
Enter measurements for both partners side by side. Great for matching wedding bands.
Partner A
Partner B
🌍 International size chart
The inner diameter and circumference of the ring in every common system.
| Diameter (mm) | Circumference (mm) | US / Canada | UK / Australia | EU (ISO) | Japan | Russia |
|---|
Features
Frequently asked questions
How accurate is the calculator?
Direct methods (string, ring, finger on screen, printable sizer) are accurate to about ±¼ size when the screen is calibrated. Detective methods are ±½ size and the anthropometric estimate is ±1 size — we show the confidence range on every result.
Is there a best time of day to measure?
Yes. Fingers swell during the day and in heat. The most reliable reading is early afternoon at a comfortable temperature. The swelling advisor above adjusts the result based on when you measured.
Can the ring size differ between my left and right hand?
Almost always. The dominant hand is typically half a size larger than the other. If you know the size on one hand you can pick the Other hand method to get the estimate for the opposite hand.
What if I have wide knuckles?
The ring needs to pass the knuckle but rest at the base of the finger without sliding off. Measure both, and either pick the knuckle size or use a European shank to secure the ring in place.
Is the AR try-on accurate?
The visual overlay is accurate enough to compare ring styles. Size inference from camera alone is an estimate (±½ size) — for precise sizing, hold a card next to your hand for reference or use a direct method.
We can — and it's free! Just send us a quick message with your idea. If you'd like to discuss it in detail, leave your email and we'll get back to you. You can stay anonymous.
