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Free Wedding Tool

Ring Size Calculator

Find your ring size by measuring an existing ring, entering a known measurement or measuring your finger at home, with instant international size conversions.

Choose your measurement method

Select the option that matches what you have available.

Measure an Existing Ring

Calibrate your screen, then match the circle to a ring that already fits.

Step 1 — Match a coin or card. Grab a coin or card, hold it against the screen, and move the slider until the outline matches it exactly.

Place Here ← Match Width →

Smaller — Larger

Calibration is required for an accurate on-screen measurement. Adjust the slider to match your US quarter. Reference width on screen

Step 2 — Lay your ring flat on the screen and match the circle to the empty opening inside it — not the outer edge

Precision on-screen sizer

Inner diameter: —

Your Size

Calibrate your screen, then drag the circle to match your ring's inner diameter. Press Show My Ring Size to see your size.

Enter Your Measurement

Already measured? Enter your ring's diameter or circumference and we'll convert it to all major sizing systems.

Ring diameter

Measure the inside of the ring, not the outside

Your Size

Enter your ring's diameter or circumference above and press Show My Ring Size.

Measure Your Finger at Home

No ring to measure yet? Find your finger's circumference with a tape measure, a piece of string, or a strip of paper.

Wrap a tape measure or string snugly around the base of your finger, where the ring will sit.
Mark or note where it meets itself after one full wrap — don't pull it tight enough to pinch.
Lay it flat against a ruler and read the length. That's your finger's circumference.

For the most reliable reading: measure at a comfortable room temperature and measure the actual finger the ring will sit on. Repeat the measurement if the result seems inconsistent.

Finger circumference

Your Size

Measure your finger above, then press Show My Ring Size.

Ring Size Chart

Diameter (mm)	Circumference (mm)	US / Canada	UK / Australia	EU / France	Brazil	Japan	Switzerland

How it works

How to Use the Ring Size Calculator

Choose the measurement method that matches what you have available. You can size an existing ring on screen, enter a diameter or circumference you already measured, or measure your finger at home with a flexible tape, string or paper strip.

The calculator matches your measurement to the closest supported ring size and shows corresponding sizes across several international systems. Because fit also depends on the ring itself and how the measurement was taken, use the result as a sizing estimate and confirm the final fit before ordering an important ring.

Choose your measurement method

Use an existing ring when you have one that already fits the intended finger, enter a known measurement when you have a diameter or circumference, or measure the finger directly when no suitable ring is available.

Measure as carefully as possible

Measure the inner opening of a ring rather than its outside edge, or wrap your measuring material snugly around the finger without pulling it tight. If you use the on-screen method, calibrate the display first.

Review the size & confirm the fit

Compare the suggested US size with the international equivalents provided by the calculator, then consider band width, knuckle size and personal fit preference before placing an order.

Measurement logic

What the Calculator Is Actually Converting

Every method ultimately provides a physical measurement. The calculator then compares that measurement with the ring-size table built into the tool.

Existing Ring Inner diameter of a ring that already fits

The relevant measurement is the empty opening inside the band, measured straight across the center.

Known Measurement Diameter or circumference

Enter the value you already have and choose mm, cm or inches where available. The calculator converts it before matching a size.

Finger Measurement Circumference around the finger

Tape, string or paper is wrapped around the area where the ring will sit, then the measured length is entered into the tool.

Size Conversion Closest supported international equivalents

The result includes US/Canada, UK/Australia, EU/France, Brazil, Japan and Switzerland sizing from the calculator's conversion table.

International sizing systems do not always map perfectly one-to-one, and individual jewelers may use slightly different charts or rounding. Confirm the seller's own size chart when ordering.

Choose your method

Which Ring Size Measurement Method Should You Use?

Start with the method that uses the most reliable information you already have. You do not need to use all three methods.

What You Have	Recommended Method
A ring that already fits the intended finger	Measure an Existing Ring
A known ring diameter	Enter a Measurement
A known finger circumference	Enter a Measurement
No ring or previous measurement	Measure Your Finger at Home

Existing ring

How to Measure a Ring You Already Own

Use a ring that comfortably fits the same finger and hand the new ring will be worn on. Ring size can differ between fingers, and even the same finger on opposite hands may not measure exactly the same.

Measure straight across the center of the inside opening. Do not include the metal of the band itself. If you use the virtual on-screen sizer instead, place the ring flat against the calibrated screen and match the digital circle to the ring's inner edge.

Finger measurement

How to Measure Your Finger at Home

Wrap a flexible tape, piece of string or narrow strip of paper around the base of the finger where the ring will sit. It should be snug enough to follow the finger without squeezing or leaving a gap.

Mark the overlap, lay the material flat and measure the length. If your knuckle is noticeably wider than the base of your finger, consider both measurements because the ring must pass over the knuckle and still sit comfortably once in place.

On-screen sizing

Screen Calibration Matters

A circle displayed on a screen has no reliable real-world size until the display is calibrated. Screen dimensions, browser scaling and device settings can all change how large an object appears.

Before using the existing-ring screen method, choose a US Quarter, US Nickel or credit card as the reference object and adjust the calibration outline until it matches the physical object as closely as possible.

Do not skip calibration.

The on-screen result depends on the calibration step. If you cannot confidently match the reference object to the screen, use a physical diameter or circumference measurement instead.

Before you order

Confirm the Final Ring Fit

Ring size is more than a number. Two rings labeled with the same size can feel different because of band width, profile, construction and how the ring sits against the finger.

Repeat any home measurement if the result seems uncertain. For engagement rings, wedding bands, wide bands or other high-value pieces, an in-person sizing with the jeweler or retailer is the best final confirmation before ordering.

Measure the actual finger and hand where the ring will be worn.

Measure when your hands are at a comfortable, normal temperature rather than very cold, overheated or immediately after exercise.

If the knuckle is significantly wider than the finger base, make sure the chosen size can comfortably pass over it.

Ask the jeweler about the specific band width, their sizing chart and available resizing or exchange options before purchasing.

Ring-size results from this tool are estimates for planning and comparison. They do not guarantee the fit of a particular ring.

Frequently asked questions

Ring Size Calculator FAQ

Quick answers about diameter, circumference, virtual sizing, band width and international ring-size conversions.

How do I calculate ring size from millimeters?

If you measured an existing ring, use its inner diameter in millimeters. If you measured your finger, use its circumference. Enter the measurement into the calculator and select the correct measurement type; the tool will match it to the closest supported ring size and show the corresponding international conversions.

What is the difference between ring diameter and circumference?

Diameter is the straight-line distance across the inside of a ring through its center. Circumference is the distance around the inside of the ring or around the finger. Mathematically, circumference is approximately the diameter multiplied by π, and the calculator can work from either measurement.

Is an online ring size calculator accurate?

It can provide a useful estimate when the input measurement is accurate. The on-screen method also depends on careful screen calibration. Measurement tension, finger temperature, knuckle size, band width and the jeweler's own sizing standards can all affect final fit, so important purchases should be confirmed before ordering.

What should I do if my measurement falls between two ring sizes?

Do not rely on a universal rule to automatically choose the larger or smaller size. The better choice depends on band width, how prominent your knuckle is, the ring's construction and how snug you prefer the fit. Check the jeweler's sizing guidance or try the relevant sizes in person when possible.

Do wider rings need a different size?

They can. A wider band contacts more of the finger and may feel tighter than a narrow band carrying the same nominal size. The amount of adjustment is not identical for every ring or person, so confirm the intended band width with the jeweler instead of applying an automatic size increase.

Are international ring size conversions exact?

Not always. Different countries use different naming and numbering systems, and conversion charts may round measurements differently. The calculator shows corresponding sizes for US/Canada, UK/Australia, EU/France, Brazil, Japan and Switzerland, but the retailer's own chart should be checked before ordering.