Find your ring size on screen
Use the free online ring sizer to match a ring you already own, or convert a measurement between six sizing systems. Get the iPhone or Android app to save measurements and preview ring styles on your hand.
iPhone · Android · Check your screen scale before measuring
Choose your free ring sizing tool
Start with what you have. These browser tools work on phones and computers without installing an app.
Match a ring on screen
Calibrate with a standard card, then match the circle to your ring’s inner opening.
Open the online ring sizer I need to measure a fingerMeasure without an existing ring
Use a paper strip or physical gauge, record the circumference and check the knuckle.
See the finger measurement steps I know a measurement or sizeConvert ring sizes
Compare US, UK, EU, Japanese, Chinese and Russian sizes, diameter and circumference.
Open the size converterA ring sizer that knows what screen it is drawing on
Physical measurements need a checked screen scale. The iPhone app uses your device model for calibration; the browser tool asks you to match a standard card first.
Measure a ring on screen
Place a ring on the display and match the adjustable circle, or use two-point tap to mark opposite inner edges for a tighter reading.
Measure a finger, no ring needed
Use the app’s guided finger or paper-strip method as an estimate, then check the knuckle and confirm with a physical gauge before an important purchase.
Scan hands-free with the camera
Follow the tool’s reference-scale and positioning instructions for a photo-assisted estimate. An ordinary hand photo alone cannot establish a ring size.
Calibrated before it draws anything
The iPhone app starts from known device-model screen density. On Android, calibrate against a physical reference. Always check the scale before measuring.
Six sizing systems, offline
Convert between US/CA, UK/AU, EU/ISO, Japan, China and Russia, and read the diameter and circumference in millimetres.
See it on your own hand
Photograph your hand once, then try on any of 30+ rings from the gallery with AI virtual try-on.
Measure, convert, browse and try on
Official Google Play screenshots, captured in English on Android. These images are not a calibrated measuring surface. App versions and reference charts may round size labels differently; keep your raw millimetre measurement and check the seller’s chart.
Three steps to a size you can order against
Check the physical screen scale
Follow the app’s calibration instructions using the specified physical reference. The iPhone app can start from device-model data; Android needs a reference check. The browser tool uses a standard card’s short edge.
Measure a ring, or measure your finger
Place a fitting ring on the calibrated display and match its inner opening. Use a ring from the intended hand and finger. Without a ring, measure finger circumference or try a physical sizing gauge, then check the knuckle fit.
Convert, save and try it on
Read your size in US, UK, EU/ISO, Japanese, Chinese or Russian, plus the diameter and circumference in millimetres. Save it with a date and a note, then see how a ring looks on your own hand.
Ring size converter
Convert between US, UK, EU/ISO, Japanese, Chinese and Russian sizes, and read the diameter and circumference in millimetres.
National sizes use the nearest chart row. A measured diameter and circumference are converted directly; check the seller’s chart and try adjacent sizes before ordering.
International ring size chart
| US / CA | UK / AU | EU / ISO | Japan | China | Russia | Diameter |
|---|---|---|---|---|---|---|
| 3 | F | 44.0 | 4 | 4 | 14 | 14.0 |
| 3.5 | G½ | 45.5 | 5 | 5 | 14.5 | 14.5 |
| 4 | H | 46.8 | 7 | 7 | 15 | 14.9 |
| 4.5 | I½ | 48.0 | 8 | 8 | 15.5 | 15.3 |
| 5 | J½ | 49.3 | 9 | 9 | 15.5 | 15.7 |
| 5.5 | K½ | 50.6 | 10 | 10 | 16 | 16.1 |
| 6 | L½ | 51.9 | 12 | 12 | 16.5 | 16.5 |
| 6.5 | M½ | 53.1 | 13 | 13 | 17 | 16.9 |
| 7 | N½ | 54.4 | 14 | 14 | 17.5 | 17.3 |
| 7.5 | O½ | 55.7 | 15 | 15 | 17.5 | 17.7 |
| 8 | P½ | 57.0 | 16 | 16 | 18 | 18.1 |
| 8.5 | Q½ | 58.3 | 17 | 17 | 18.5 | 18.6 |
| 9 | R½ | 59.5 | 18 | 18 | 19 | 18.9 |
| 9.5 | S½ | 60.8 | 19 | 19 | 19.5 | 19.4 |
| 10 | T½ | 62.1 | 20 | 20 | 20 | 19.8 |
| 10.5 | U½ | 63.4 | 22 | 22 | 20 | 20.2 |
| 11 | V½ | 64.6 | 23 | 23 | 20.5 | 20.6 |
| 11.5 | W½ | 65.9 | 24 | 24 | 21 | 21.0 |
| 12 | Y | 67.2 | 25 | 25 | 21.5 | 21.4 |
| 12.5 | Z | 68.5 | 26 | 26 | 22 | 21.8 |
| 13 | Z+1 | 69.7 | 27 | 27 | 22 | 22.2 |
Ring sizing guides
Twenty-four step-by-step guides covering every way to find a ring size, and every way it usually goes wrong.
How to measure your ring size at home
Five ways to measure ring size at home, ranked by accuracy, plus the calibration step that decides whether any of them actually works.
Read the guideGuideRing size chart for US, UK, EU, Japan, China and Russia
The complete international ring size chart with millimetre diameters and circumferences, plus how to read it and which column your seller actually means.
Read the guideGuideRing size converter
Convert US, UK, EU, Japanese, Chinese and Russian ring sizes. Enter diameter or circumference in millimetres and compare the closest chart sizes for free.
Read the guideGuideRing size scanner: scan a ring or finger with your phone
Use a ring size scanner correctly: choose ring or finger mode, set a clean reference scale, control light and angle, then verify before ordering.
Read the guideGuideCalibrated on-screen ring sizer
Calibrate this on-screen ring sizer with a payment card, match a ring’s inner opening, and get the closest US, UK and EU size without printing.
Read the guideGuideRing size by finger: thumb, index, middle, ring and pinky
Learn why every finger needs its own ring-size measurement, with practical fitting advice for thumb, index, middle, ring and pinky rings.
Read the guideGuideJapanese ring size to US conversion
Convert Japanese ring sizes to the nearest US size, then verify the result using inner diameter or circumference before ordering internationally.
Read the guideGuideSmart ring size guide for a secure, comfortable fit
Choose a smart-ring size with the correct model-specific kit, a full-day wear test and fit checks that protect comfort and sensor contact.
Read the guideReading on rings, fit and sizing
Practical articles on measuring, saving sizes, fit problems, materials and buying online, with app tutorials in seven languages.
The best time of day to measure your ring size
Measure when your hands feel normal—not at one magic hour. See when to wait after heat, cold or exercise, how often to check and which result to use.
Read the articleFitWhy is my right ring finger bigger than my left?
Right ring finger bigger than your left? Compare knuckle shape, stable differences and swelling, then use the two-hand fit check before choosing a ring size.
Read the articleProposalsCan you find ring size from a photo?
Learn when a photo cannot reveal ring size, when a scaled existing-ring photo can support an estimate, and how to avoid perspective and lens errors.
Read the articleConversionWhat ring size is 17 mm?
A 17 mm inner diameter is closest to US 6½ and UK M½, with a 53.4 mm circumference. Compare nearby sizes and convert your exact measurement before buying.
Read the articleFitHow much does ring size change after weight loss?
Weight loss can loosen a ring, but pounds do not convert to ring sizes. Check whether the change is lasting, secure a loose band and decide when to resize.
Read the articleApp tutorialsRing Sizer for Android: from first measurement to a useful size record
Use Ring Sizer on Android to calibrate your screen, estimate an existing ring, check millimetres and save a useful record before buying jewellery.
Read the articleRing sizing questions, answered
How do I measure my ring size at home?
Measure the inner diameter of a ring that already fits and match it to a size chart. 17.3 mm is a US 7. If you have no ring, measure the circumference at the base of your finger instead. Either way, use a calibrated scale and repeat the measurement on ordinary days when your hands feel comfortable. Avoid relying on a reading taken just after unusual heat, cold, exercise or visible swelling.
Is a ring sizer app actually accurate?
It depends entirely on calibration. A 17.3 mm circle is 313 pixels on a 460 PPI iPhone and 222 on a 326 PPI one, so an app that assumes a single generic screen density can be several sizes out. Ring Sizer reads your device model and sets its scale from that screen’s known PPI, and shows you which device and density it used. The result is still an estimate: check it with an independent method and, before an important order, try the seller’s adjacent sizes in the intended band width.
How do I measure ring size without a ring sizer?
Wrap a non-stretchy paper strip around the base of your finger, mark the overlap and measure the marked length in millimetres. That is your inner circumference, and 54.4 mm maps near a US 7. Paper can shift or compress, while string can stretch or twist, so keep the raw measurement and repeat it rather than assuming either material creates a fixed amount of error.
What is the average ring size?
Some retailers report that women’s rings commonly sold cluster around US 6 to 7 and men’s around US 9 to 10, but sales ranges reflect a retailer’s market, customers and inventory; they are not biological averages. Use a reported range only to question an implausible reading, never to infer one person’s size.
How do I convert a US ring size to UK or European?
A US 6 is a UK L½ and an EU/ISO 51.9; a US 7 is a UK N½ and an EU/ISO 54.4. European sizes are the ring’s inner circumference in millimetres, which is why they look so different from US numbers. Convert once, directly from your measurement, because converting twice rounds twice.
What ring size is 17 mm?
A 17.0 mm inner diameter has a 53.4 mm circumference and maps nearest to US 6½ and UK M½. If your 17 mm is a circumference rather than a diameter, it is not a ring measurement: ring circumferences run from about 44 mm to 70 mm.
How can I find out her ring size secretly?
Borrow a ring she already wears on the correct finger and measure its inner diameter. It takes under a minute and it is the only method that measures the actual target. If that is impossible, photograph the ring next to a credit card, or ask the person in her life who can keep a secret.
Do I need to print anything?
No. Printable sizers only work if they print at exactly 100% scale, and printer drivers routinely apply “fit to page” without telling you. Near US 7, a 2% diameter error is about 0.35 mm, roughly 0.4 of a US size. Ring Sizer sets its scale from your device instead, but you should still verify its calibration.
Should I size up for a wide band?
A wide band can feel tighter than a narrow ring with the same inner diameter, but there is no universal half-size or full-size correction. Try adjacent sizes in a sample matching the intended width and inside profile, then choose the one that clears the joint, sits securely and remains removable.
What if my knuckle is bigger than my finger?
Measure both the knuckle and the base, then test adjacent sizes because the ring must clear the joint and still sit securely below it. There is no fixed size-gap threshold that chooses the answer. If an ordinary size cannot do both, ask a jeweller about options compatible with that ring’s construction.
When is the best time of day to measure?
There is no universal best clock time. Measure when your hands feel comfortable and ordinary, not just after unusual heat, cold, exercise or visible swelling. Repeat the same calibrated method on different ordinary days, keep the range and confirm adjacent sizes in the intended ring width.
Can I see a ring on my hand before I buy it?
Yes. Photograph your hand once, flat, fingers spread, in indirect daylight, and Ring Sizer’s AI virtual try-on will render any ring from the 30+ gallery onto it. It answers whether a setting suits your hand. It cannot measure your finger; nothing in a photograph can.
Which sizing systems does Ring Sizer support?
US/Canada, UK/Australia, EU/ISO, Japan, China and Russia, plus the inner diameter and circumference in millimetres. Millimetres are the value to send a jeweller if you are ordering somewhere whose sizing you do not recognise, because every jeweller in the world can work from them.
Is Ring Sizer free?
Ring Sizer is free to download from the App Store and includes optional in-app purchases. It runs on iPhone with iOS 17.0 or later. An Android version is also available on Google Play with in-app purchases; check that listing for device compatibility and current offers.
Get your ring size right the first time
Available on the App Store and Google Play. Measure ring sizes, convert between systems, save measurements and preview styles on your hand.