01
Calibrate
Place a credit card (or local coin) on screen and match it to the outline. We save that scale for future measurements on this device.
Free · calibrated · no sign-up
Measure your ring size.
Measure your ring size.
Right on your screen.
Place a ring you already own on the display and match its inner edge—or measure your finger with a paper strip. This free virtual ring sizer calibrates to your device, then converts the result to US, UK, EU and JP sizes instantly.
Calibrated to your screen
US · UK · EU · JP sizes
Works on phone, tablet, desktop
Nothing is uploaded — fully private
1Start
2Calibrate
3Measure
4Result
How it works
Three quick steps to a useful ring-size estimate. Average time: under 2 minutes.
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1
Calibrate Hold a credit card on the screen and match the on-screen outline. Done once, saved forever.
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2
Measure Place a ring you own on the screen and match the inner edge — or, if you don't have a ring, measure your finger with a strip of paper.
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3
Get your size See your size in US, UK, EU and JP — plus diameter and circumference in millimetres.
Already know your size? Jump to the full conversion chart
Calibrate your screen
So the on-screen ring reflects real-world millimetres on this device.
Place a US Quarter flat against the screen and adjust the slider until its outer edge matches the outline.
↔ Scroll the outline if it extends past the screen — the size shown is physically accurate.
Tips for accurate calibration
Ensure your browser zoom is 100%.
Match the object's outer edge to the dashed outline.
Place the object directly on the screen (no case or sleeve).
Use good lighting and look straight on, not at an angle.
Re-calibrate if you switch devices.
Match the object's outer edge to the dashed outline.
Place the object directly on the screen (no case or sleeve).
Use good lighting and look straight on, not at an angle.
Re-calibrate if you switch devices.
Place your ring on the screen
Drag the slider until the gold circle matches the inner edge of your ring. Re-calibrate screen
Use ← → arrow keys for fine adjustment
Measure your finger
1 — Wrap a thin strip of paper around your finger. 2 — Mark where the end meets. 3 — Lay the strip flat on the ruler with one end at 0, then drag the marker to your pen mark. The number is your finger's circumference in millimetres. Re-calibrate screen
Ruler is in millimetres — line up the strip's start at 0, then drag the marker to your mark
Circumference 57.0 mm
· US Size 8
Your ring size
Based on your measurement — saved automatically.
US Ring Size
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US
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UK
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EU
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Tip: for eternity bands or wide settings, consider adding ½ size.
Shop rings in US size
Browse rings for your measured size
Links open Amazon in a new tab. As an Amazon Associate we earn from qualifying purchases.
¼ sizes
Fine size incrementsUS · UK · EU · JP
Size conversions100%
On-device · nothing uploaded$0
No install · runs in your browser
How it works
A calibrated online ring sizer, in three steps.
Unlike a generic image-based chart, RingSize.app calibrates to your screen before you compare a ring or paper strip.
02
Measure
Place an existing ring on screen and adjust until the inner edges line up — or, if you don't own a ring, measure your finger circumference with a paper strip on our calibrated ruler.
03
Convert
Read the closest size in US, UK, EU and Japanese standards, with diameter and circumference in millimetres.
International conversion
A quick look at the ring size chart.
Diameter and circumference in millimetres, mapped to US, UK and European standards. Need every half-size and Japanese conversions? Open the full chart →
| US | UK | EU | Diameter (mm) | Circumference (mm) |
|---|---|---|---|---|
| 5 | J | 49 | 15.7 | 49.3 |
| 6 | L | 51.5 | 16.5 | 51.9 |
| 7 | N | 54 | 17.3 | 54.4 |
| 8 | P | 57 | 18.1 | 57.0 |
| 9 | R | 59 | 19.0 | 59.5 |
| 10 | T | 62 | 19.8 | 62.1 |
| 11 | V | 64 | 20.6 | 64.6 |
| 12 | X | 66.5 | 21.4 | 67.2 |
FAQ
Common questions about our free ring size app.
How accurate is the free ring size app with actual ring size chart on screen?
Calibration makes the on-screen outline reflect real-world millimetres on your device. Accuracy still depends on careful alignment, browser scaling, and the ring or paper strip you use, so confirm valuable or non-resizable purchases with a jeweller.
What objects can I use for calibration?
You can use local coins or a standard ID-1 credit/debit card (85.60 × 53.98 mm): US Quarter (24.26 mm), 1 Yuan (25.00 mm), 1 Euro (23.25 mm), Canadian 25¢ (23.88 mm), ₹5 Rupee (23.00 mm), $1 AUD (25.00 mm) or $1 SGD (24.66 mm). The app automatically detects your region and suggests the most universal option.
Does the free ring sizer app work on mobile phones?
Yes — our free ring sizer app works on every modern smartphone, tablet and desktop browser. The actual ring size chart on screen adapts to any device and re-uses your saved calibration so you only need to set it up once per screen.
Is the ring size app really free?
Yes — completely free. There's no registration, no download, and no paywall. We may earn a small commission if you choose to buy a ring or sizing tool through our partner links, which helps keep the sizer free.
Can I measure different fingers with this tool?
Absolutely. The tool measures circumference — which is the universal language of ring size — so it works for any finger. For eternity bands or unusually wide settings, we recommend rounding up by ½ size.
What's the best time of day to measure ring size?
Fingers swell slightly through the day and in warm weather. For the most reliable fit, measure in the late afternoon or evening at a normal room temperature — that's how you'll wear the ring most of the time.
How is this different from a virtual ring sizer or digital ring sizer image?
A printed or static "virtual ring sizer" image only works if the printer or screen reproduces it at exactly 100% scale — which it rarely does. RingSize.app is a true digital ring sizer because it calibrates to your specific screen using a credit card or coin, so the actual ring size on screen matches real millimetres on any device.
Can I use this as an actual ring size chart on my phone?
Yes — the actual ring size chart on phone view is fully supported. Calibrate using a credit card pressed against your phone screen, then place your ring directly on the display. You can also tap "Send to phone" on desktop to get a QR code that opens the sizer on your mobile.
Is there an actual ring size chart for women's and men's rings?
Ring sizes are universal — there is no separate scale for women's vs men's rings. The same US/UK/EU sizing applies to both. Women's ring sizes most commonly fall between US 5 and 7; men's between US 9 and 11. Our ring size calculator covers US 3 through 13 (UK F through Z, EU 44 – 69) for everyone.
Does the actual ring size chart on screen work in the UK?
Yes. Calibrate with any standard ID-1 credit/debit card (85.60 × 53.98 mm — same dimensions worldwide) and you'll see the actual ring size chart on screen UK users expect. The result panel converts your size to UK letter sizes (F – Z), EU and JP standards automatically.
Can I measure ring size on phone for free?
Yes — measuring ring size on phone is free with no installation. Open ringsize.app in your mobile browser, calibrate with a credit card, and place a ring on the screen. There is no app to download and nothing leaves your device.
Why RingSize.app
Why calibrating the screen matters.
Why an on-screen ring sizer needs calibration
A static ring chart assumes every screen displays a millimetre at the same scale. They do not. RingSize.app first asks you to match a known object—a standard card or local coin—so the ring and ruler are scaled for your device. Your calibration remains in this browser for future measurements.
Two ways to measure at home
If you have a ring that fits the intended finger, place it on the screen and adjust the gold circle until it meets the ring's inner edge. If you do not have a ring, wrap a narrow paper strip around your finger, mark the overlap, and compare it with the calibrated ruler. The result includes the closest US size plus UK and EU conversions, diameter, and circumference.
Built for useful results
- US sizes 3–13 in quarter-size increments
- UK, EU and Japanese conversions
- Diameter and circumference in millimetres
- No account, download, or paywall
- Measurements stay on your device
Measure under the right conditions
- Measure at normal room temperature
- Try again later in the day if your fingers swell
- Keep the paper strip snug, not tight
- Consider half a size up for wide bands
Use it on your phone—nothing to install
Open RingSize.app in a modern mobile browser, calibrate that screen, and place your ring directly on the display. Desktop users can choose Send to phone to open the same flow from a QR code. For an important purchase, confirm the result with a jeweller or a physical ring sizer set.