Free iPhone ring sizer app: measure a ring on screen, measure finger width, convert US, UK, EU, JP and letter sizes, and save sizes in seconds.
5.84k+ downloads · 4.8 stars
Updated iPhone interface
The updated app keeps ring measurement, finger measurement, conversion, and saved sizes cleanly connected.
Measure a ring, measure a finger, convert standards, and save sizes without visiting a jeweler.
Ring Measurement
Place a ring on the circle and adjust the guide until the inner edge matches.
Saved Sizes
Keep important ring sizes ready for yourself, family, partners, and gift planning.
Global Size Standards
Convert between US, UK, EU, Japan, Australia, India, and millimeter measurements.
Finger Width Mode
No ring? Measure your finger directly across the on-screen bar and fine-tune the millimeter value.
Offline & Private
Works fully offline. Your data never leaves your device. Zero tracking.
Instant Results
Your size appears immediately in all major standards — US, UK, EU, and more.
Engagement Ready
Planning a surprise proposal? Secretly measure a ring while they're away.
Size History
Track how your ring size changes over time with measurement history.
Clean iPhone UI
Large controls, clear rulers, and focused sheets make each sizing task easy to follow.
Use our free online tool. No download needed.
Step 1: Calibrate Your Screen
Place a standard credit card on your screen for pixel density calibration.
Place your ring on the screen and drag the handles to match its inner edge.
Your Ring Size
-
US Size
-
UK Size
-
EU Size
-
Japan Size
-
Diameter (mm)
Tip: Calibrate your screen with a credit card first for maximum accuracy. Want size history, family profiles, and advanced features? Download the app.
A standard credit card is 85.6mm wide. Drag the handles to match your card's width exactly.
No jeweler visit. No guesswork. Just your phone.
Choose a Mode
Measure an existing ring on the circle, or switch to finger width mode when no ring is available.
Align the Guide
Use the ruler, slider, and plus/minus controls to match the ring or finger width precisely.
Save or Convert
See the measurement instantly, save it for later, or convert it between international standards.
Buy jewelry anywhere in the world with confidence.
US
& Canada
UK
& Australia
EU
Europe
JP
Japan
IN
India
mm
Diameter
Ring Sizer works entirely offline. Your measurements never leave your device. We don't collect, share, or sell any of your data. Ever.
"Used this app to measure ring size. It's accurate and it's really helpful."
Pradep12 · App Store Review
Our app uses precise screen calibration to match your ring to on-screen guides, ensuring highly accurate results comparable to professional jeweler tools.
No external tools or printouts are required. Use your phone screen to measure a ring, measure finger width, or convert a known size.
Ring Sizer supports multiple regional size systems including US/Canada, UK, Europe, Japan, India, Australia, and more.
Yes. All measurements are stored locally on your device and the app works completely offline. We never collect, share, or sell your data.
Yes. Ring Sizer is a free ring sizer app for iPhone that lets you measure your ring size on your phone screen in seconds. Place a ring on the circle or measure finger width, then get your size in US, UK, EU, JP, and other standards. No tools or paper needed.
Absolutely. With the Ring Sizer app, you place your existing ring directly on your iPhone screen and use the on-screen circle guide to match the inner diameter. You can also measure finger width directly in the updated app UI.
UK ring sizes use letters (A–Z) while US sizes use numbers (1–13+). For example, UK J = US 5, UK L = US 6, UK N = US 7, and UK P = US 8. For exact conversions, use our UK to US ring size converter or check the full ring size chart.
The average women's ring size in the US is 6 to 6.5 (UK L–M), while the average men's ring size is 10 to 10.5 (UK T–U). However, ring sizes vary significantly by individual — your best bet is to measure accurately using a ring sizer app rather than guessing based on averages.
Guides, tools, and charts to help you find the perfect fit.
Ring Size Chart
Complete conversion chart for US, UK, EU, Japan, and Australian ring sizes with diameter in mm.
How to Measure Ring Size at Home
5 free methods to find your ring size without visiting a jeweler — app, string, paper strip, and more.
Ring Size Calculator
Enter your ring diameter or circumference to instantly find your size in every international standard.
UK Ring Sizes (A–Z)
British letter-based sizing guide with full chart, Hatton Garden tips, and UK to US conversion.
Men's Ring Size Guide
Average men's ring sizes, measurement tips, and a complete chart for wedding bands and signet rings.
Secret Engagement Ring Sizing
How to find your partner's ring size without them knowing — clever tips for surprise proposals.
Free to download. Works on iPhone. No tools needed.
