リングサイズ計算ツール

You can measure your ring size at home using three reliable methods:

• On-Screen Ring Sizer: Place an existing ring directly on our calibrated virtual ring sizer using a credit card or coin for 1:1 screen calibration.
• Paper Strip or String: Wrap a non-stretchy strip of paper snugly around your finger base and knuckle, mark where it overlaps, measure the length in millimeters with a ruler, and match it to our ring size chart.
• Printable Ring Sizer: Download and print our 100% scale free printable ring sizer PDF to measure with cut-out circles or paper sizing strip.

Yes! FreeRingSizer.com is fully optimized for smartphones (iPhone Safari, Android Chrome, and all mobile browsers). Simply open the online ring sizer on your phone, calibrate your display using any standard card (credit card, ID, or driver's license) or local coin, and place your ring directly on the screen circle to get an instant reading.

Yes, FreeRingSizer.com is a 100% free virtual ring sizer that operates entirely in your browser without requiring app downloads or account registration. It includes millimeter-precise screen calibration, an interactive ring sizing circle, an on-screen paper ruler, and instant conversion across 15+ international sizing standards including US, UK, EU, and India.

You can find out your ring size in 4 quick ways:

1. Measure an Existing Ring: Place a ring that fits on our interactive on-screen sizer to measure its inside diameter.
2. Measure Your Finger Circumference: Wrap a paper strip around your finger knuckle, note the length in mm, and input it into our Ring Size Calculator.
3. Print a Paper Sizer: Download our Printable Ring Sizer PDF for accurate physical circle cutouts.
4. Visit a Local Jeweler: Try professional metal mandrel sizing rings for an in-person confirmation.

A standard US Size 7 ring has an inside diameter of 17.3 mm (0.681 inches) and an inside circumference of 54.4 mm (2.14 inches). Internationally, a US Size 7 corresponds to:

• UK / Australia: Size N½ or O
• Europe (ISO 8653): Size 54 or 55
• India, Japan & China: Size 14
• Germany / Switzerland: 17.3 mm diameter

US Size 7 is the most popular average women's ring size worldwide.

Yes, you can print our free ring sizer directly from our Printable Ring Sizer Page. When printing, select "Actual Size" or 100% Scale in your print settings (disable "Fit to Page"). The printable guide includes both circle comparison templates and a cutout paper ring measuring strip, plus a 50mm and 2-inch calibration check bar to guarantee 100% accuracy.

To check your finger ring size online for free:

1. Navigate to FreeRingSizer.com on any phone, tablet, or laptop.
2. Calibrate your screen scale with any bank card, driver's license, coin, or ruler.
3. Switch to the Finger Measurement tab to use the on-screen millimeter ruler with a marked paper strip, or place an existing ring over the digital circle.
4. Instantly view your calculated size in US, UK, EU, Indian, and other global standards.

FreeRingSizer.com is widely considered the best web-based ring sizer utility because it provides all the capabilities of native mobile apps without requiring any downloads, app store installations, or storage space. It offers sub-millimeter screen calibration, multi-coin and card support, a smooth interactive circle slider, and an extensive international conversion table for 15+ countries.

If you cannot measure directly, here are 4 proven ways to estimate ring size:

• Use Averages: The average women's ring size is US 6 to 7; the average men's ring size is US 9 to 10.
• Check Past Jewelry: Check previous ring orders, jewelry receipts, or inner band stamps (some rings have size engravings inside).
• Compare with Friends/Family: Have a friend or relative of similar build try on a known ring size.
• Secretly Borrow a Ring: Temporarily borrow a ring worn on the same finger and place it on our virtual sizer.

You can get an instant free ring sizer right here on FreeRingSizer.com. We provide an interactive on-screen sizer, a digital ring size calculator, and a free downloadable PDF printable ring sizer that you can print at home in seconds without waiting for mail delivery or paying shipping fees.

Using an online ring sizer tool is simple:

1. Open FreeRingSizer.com: Access the tool on your mobile phone or desktop browser.
2. Calibrate: Align a physical credit card or coin with the on-screen calibration graphic to lock in 1:1 real-world pixels.
3. Place Ring: Set your ring flat on the screen over the circle graphic.
4. Adjust Slider: Move the slider until the digital circle matches the inside rim of the ring.
5. Read Result: Instantly read your US, UK, EU, or Indian ring size.

To secretly find your partner's ring size for an engagement or surprise gift:

• Borrow an Existing Ring: Take a ring they wear on the intended finger, place it on our on-screen sizer, or trace the inner circumference on paper.
• Press into Soap or Clay: Make a clean impression of their ring in a bar of soap or modeling clay to measure later.
• Ask Friends or Family: Inquire with their mother, sister, or best friend who may already know or can casually ask during shopping.
• Try It on Your Own Finger: Slide their ring onto your finger, mark where it stops with a pen, and measure that spot on our finger ruler.

A finger circumference of 7 cm (70 mm) corresponds to a US Ring Size 13.5 to 14 (UK Size Z+1, European Size 70, Indian Size 28). If 7 cm refers to diameter (70 mm), that is the dimension of a wrist bangle or bracelet, as human finger ring diameters typically range from 14 mm to 23 mm.

Ring size numbers correspond to specific millimeter measurements. In the standard US & Canada numbering system:

• Size 4: 14.9 mm diameter (46.8 mm circumference)
• Size 5: 15.7 mm diameter (49.3 mm circumference)
• Size 6: 16.5 mm diameter (51.9 mm circumference)
• Size 7: 17.3 mm diameter (54.4 mm circumference)
• Size 8: 18.1 mm diameter (57.0 mm circumference)
• Size 9: 19.0 mm diameter (59.5 mm circumference)
• Size 10: 19.8 mm diameter (62.1 mm circumference)
• Size 11: 20.6 mm diameter (64.6 mm circumference)

Check our full International Ring Size Chart for sizes 3 through 15 in half-size increments.

7 inches (177.8 mm) is the measurement of a standard wrist bracelet, not a finger ring! Finger circumferences typically measure between 1.73 inches (44 mm, US size 3) and 2.74 inches (70 mm, US size 14). If you measured 7 cm (2.75 inches), that corresponds to US Size 13.5–14.

There are two perspectives depending on which system you start from:

• A US Size 7 corresponds to Size 14 in India (inside diameter 17.3 mm, circumference 54.4 mm).
• An Indian Size 7 corresponds to US Size 4 (UK Size H, inside diameter 14.9 mm, circumference 46.8 mm).

Use our Ring Size Calculator to switch instantly between Indian and US sizing standards.

No, a size 7 ring is not big for a woman. In fact, US Size 7 is the single most common average women's ring size in the United States and Canada (the typical range is size 6 to 7). It fits comfortably on most average-build women's ring fingers.

For women, US size 7 is standard average, not small. For men, US size 7 is considered small for an average ring or middle finger (average men's ring size is US 9 to 10), though it frequently fits men's pinky fingers or slender hands.

To use a ring sizer correctly:

• Digital/Screen Sizer: Place a credit card on your display to calibrate 1:1 scale, place your ring over the digital circle, and adjust the slider until the outline matches the inside edge of your ring band.
• Plastic Belt / Zip Sizer: Slip the end through the buckle to create a loop, slide it onto your finger, pull until comfortably snug, and verify it can slide smoothly over your knuckle. Read the size indicated by the arrow.

To read a ring sizer accurately:

1. Ensure you are reading the inside diameter (inner edge to inner edge), ignoring the thickness of the metal ring band.
2. On plastic belt sizers, read the line or letter directly pointed to by the buckle arrow when snug.
3. Check which regional system you are viewing: US/Canada uses numbers (3–15), UK/Australia uses letters (A–Z), and EU uses millimeter circumference (44–75).

You can easily measure without any specialized tool using the household paper strip method:

1. Cut a strip of paper 1 cm wide and 10 cm long.
2. Wrap it comfortably around the base of your finger and across your knuckle.
3. Mark the exact point where the paper overlaps with a fine pen.
4. Lay the strip flat against a ruler to measure millimeters.
5. Compare this millimeter circumference to our Ring Size Chart or enter it into our Ring Size Calculator.

To measure using our Ring Size Calculator:

1. Select your measurement unit: Millimeters (mm), Centimeters (cm), or Inches (in).
2. Choose whether you measured an Inner Diameter (existing ring) or Circumference (finger paper strip).
3. Type in your value or use our on-screen paper strip ruler.
4. The calculator automatically outputs your exact size across US, UK, European ISO, Indian, Japanese, and Australian systems.

To measure using a ring size chart:

1. Find your finger circumference or inner ring diameter in millimeters.
2. Locate that measurement in the first column of our Ring Size Chart.
3. Follow the row across to read your corresponding regional size (e.g. 17.3 mm = US 7 = UK O = EU 54.4 = India 14).
4. If your measurement falls between two sizes, always choose the larger size for comfort.

Our ring size calculator is built upon international jeweler standard ISO 8653. It uses mathematical conversions (Circumference = π × Diameter) and regional calibration offsets to convert millimeter and inch measurements into global ring sizes with zero rounding error, ensuring perfect fit whether shopping online or at luxury boutiques.

The most accurate ring size calculator is one with physical screen calibration like FreeRingSizer.com. Standard online tools fail because screen pixel density varies between devices. FreeRingSizer.com uses standard bank cards (ISO/IEC 7810 ID-1 standard: 85.60 mm) or coins to calibrate your screen pixels to 1:1 real-world dimensions, achieving sub-0.5mm jeweler-grade accuracy.

To measure at home using our printable chart:

1. Open our Printable Ring Sizer and click Print.
2. Set scaling to 100% (do not select "Fit to Page").
3. Verify the printed scale line with a credit card or physical ruler.
4. Place your ring over the printed circles until the inner diameter matches the circle line, or cut out the paper sizer strip to wrap around your finger.

You can find a complete, searchable international conversion chart at FreeRingSizer.com/ring-size-chart. It supports US, UK, Europe (ISO 8653), India, Japan, China, Australia, Germany, Brazil, and 10+ other regional standards with both millimeters and inches.

To measure using a diameter chart:

1. Take a physical ruler and measure the widest inside opening of your ring in millimeters (do not include the ring band metal).
2. Look up your diameter on our chart:
   • 15.7 mm = US 5
   • 16.5 mm = US 6
   • 17.3 mm = US 7
   • 18.1 mm = US 8
   • 19.0 mm = US 9
   • 19.8 mm = US 10
3. Check our Full Diameter Chart for all standard and half sizes.

To calculate your US ring size mathematically without a chart:

1. Measure your finger circumference in millimeters with a paper strip and ruler.
2. Calculate inside diameter: Diameter = Circumference ÷ 3.14159
3. Apply the US formula: US Size = (Diameter in mm - 11.54) ÷ 0.83
4. Or simply enter your number into our instant Ring Size Calculator to get your exact size automatically.

A ring size chart is a standardized jewelry reference guide that maps inner ring diameter and finger circumference (measured in millimeters or inches) to international sizing scales (such as US numbers, UK letters, European ISO circumference, and Asian sizes). It enables shoppers and jewelers to ensure a comfortable fit across different brands and countries.

A "What size ring do I wear" chart connects your physical finger measurements to your regional size. For quick reference:

• Small Hands (Women US 4–5 / Men US 7–8): 14.9 mm to 15.7 mm diameter
• Medium / Average (Women US 6–7 / Men US 9–10): 16.5 mm to 17.3 mm diameter (women) or 19.0 mm to 19.8 mm (men)
• Large Hands (Women US 8–9 / Men US 11–12): 18.1 mm to 19.0 mm diameter (women) or 20.6 mm to 21.4 mm (men)

View our interactive International Ring Size Chart to find your exact match.