Ring Size Calculator | Find Your Size Online
Free Ring Size Calculator

Find Your Ring Size in Under a Minute

Measure an existing ring, enter a known measurement, or measure your finger at home. Get your US size and international conversions instantly.

For guidance only. Confirm the final fit with a jeweler before ordering a high-value ring.

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 (easiest — fits any screen) or a card, hold it against the screen, and move the slider until the outline matches it exactly.

Place Here ← Match Width →

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

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 Calculate 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.

INNER DIAMETER

Measure the inside of the ring, not the outside

Your Size

Enter your ring's diameter or circumference above and press Get My 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 — whatever you have on hand.

  1. Wrap a tape measure or string snugly around the base of your finger, where the ring will sit.

  2. Mark or note where it meets itself after one full wrap — don't pull it tight enough to pinch.

  3. Lay it flat against a ruler and read the length. That's your finger's circumference.

For the most reliable reading: measure at room temperature, later in the day, and measure the actual finger the ring will sit on — width varies across the hand. Measure 2–3 times and use the largest result.

Your Size

Measure your finger's circumference above, then press Get My Size.

Ring Size Chart
Diameter (mm)Circumference (mm)US / CanadaUK / AustraliaEU / FranceBrazilJapanSwitzerland

Between two sizes? If your measurement falls between two sizes, the larger one is often more comfortable — especially for wider bands. It's not an absolute rule: the right call also depends on band width, knuckle size, and personal preference, so confirm with the jeweler before ordering a high-value ring.

Wider bands fit tighter. If your ring is more than 6mm wide, go half a size up to account for the extra material across the knuckle.

Knuckle vs base. If your knuckle is noticeably wider than the base of your finger, measure both and choose a size in between — or ask your jeweler about hinged ring shanks.

Temperature matters. Cold weather can make fingers up to half a size smaller. Measure at room temperature in the afternoon for the most accurate result.

Which Method Is Best for You?

SituationBest Method
I already have a ring that fitsMeasure an Existing Ring (on-screen)
I already know the diameter or circumferenceEnter a Measurement
I only have my finger to measureMeasure Your Finger at Home
I'm buying a surprise engagement ringMeasure an Existing Ring (borrow one that fits)
TipMeasure your finger in the evening, when it's at its largest.
TipCold fingers measure smaller — warm up first.
TipWide bands fit tighter than thin ones at the same size.
TipMeasure two or three times and use the average.

How to Measure Ring Size

There are a few reliable ways to find a ring size at home, depending on what you have on hand.

Using an existing ring

If you already own a ring that fits the intended finger, that's the most reliable reference. Lay it flat and measure the inner diameter — the empty space inside the band, not the metal itself — or use the on-screen tool above to match it directly.

Using string or a strip of paper

Wrap a piece of string or a thin strip of paper snugly around the base of the finger, mark where it overlaps, then measure that length with a ruler. That gives you the finger's circumference, which the calculator above converts into a size.

Using a tape measure

A flexible sewing tape measure works the same way as string, but gives you a circumference reading directly without needing a separate ruler step.

How Accurate Is an Online Ring Size Calculator?

An online calculator is generally accurate to within about half a size, provided the input measurement is precise. Accuracy depends on three main factors:

  • Calibration — for on-screen tools, the circle has to be scaled to your monitor's real pixel density using a known reference like a credit card.
  • Measurement technique — inconsistent tension on string or paper, or measuring over a knuckle instead of the base of the finger, throws off the result.
  • Band width — a wide band fits differently than a thin one at the same nominal size, which no calculator can fully account for without knowing the exact ring.

For everyday jewelry, this level of accuracy is enough to order with confidence. For a high-value engagement ring or wedding band, we'd still recommend a final check with a jeweler's sizing tool before the order ships.

Common Ring Size Measuring Mistakes

  • Measuring a cold finger. Cold temperatures cause fingers to shrink temporarily — measure at room temperature, ideally in the afternoon or evening.
  • Measuring right after exercise. Physical activity can temporarily swell fingers, giving a larger-than-normal reading.
  • Measuring over the knuckle instead of the base. The knuckle is often wider than the base of the finger — measure both if they differ significantly.
  • Measuring the outer edge of a ring instead of the inner opening. Only the inner diameter tells you the actual finger size.
  • Skipping screen calibration. On-screen sizing tools rely on knowing your monitor's real pixel density; skipping this step makes the result meaningless.

Ring Width Matters

A ring's band width changes how it fits, even at the same labeled size. Wider bands (around 6mm or more) press against more of the finger's surface and tend to feel tighter, so it's common to size up half a size for a wide band compared to a thin one. If you're switching from a thin band you already own to a wider style, keep this in mind rather than assuming the same size will fit.

When Should You Size Up?

Size up if: your band is wider than about 6mm, your knuckle is noticeably larger than the base of your finger, you tend to retain water or your finger size fluctuates, or your measurement fell almost exactly between two sizes. A ring that's slightly loose can be resized down inexpensively; one that's too tight is uncomfortable and usually more costly to resize.

Ring Sizes for Men vs. Women

There's no separate men's or women's sizing system — the same US, UK, and international scales apply to everyone, based purely on finger circumference. That said, average sizes differ by population:

Did you know? The average women's ring size in the U.S. is around 6–7, while men's wedding bands are most often 9–10 — but individual variation is wide enough that measurement always beats guessing from averages.

International Ring Size Guide

Ring sizing conventions vary by country, which is why the same physical ring can carry different numbers depending on where it's sold:

  • US / Canada — numerical scale (typically 3–13, with half sizes), based on inner circumference.
  • UK / Australia — letter-based scale (A–Z, extending to Z+1, Z+2 for larger sizes).
  • EU / France — numerical scale based directly on inner circumference in millimeters.
  • Japan — numerical scale on its own progression, distinct from both US and EU systems.
  • Brazil — numerical scale commonly used across Brazilian jewelers, distinct from the US and EU numbers.

Because none of these convert with a simple formula, always use a conversion chart — like the one above — rather than assuming a size number carries over between countries.

Buying an Engagement Ring as a Surprise?

Getting an accurate size without tipping off your partner takes a little more creativity, but it's very doable:

  • Borrow a ring they already wear on the correct finger (even briefly) and measure or scan it using the on-screen method above.
  • Ask someone close to them — a family member, roommate, or friend — who may already know or can find out discreetly.
  • Trace a ring while they sleep as a rough backup, though this is the least precise option and shouldn't be your only data point.
  • Order slightly larger and plan to resize. Most jewelers offer a free or low-cost resize within the first year — a safety net if your estimate is off by half a size.

How We Calculate Ring Size

This calculator follows standard US ring sizing, based on the inner circumference of the ring in millimeters. From that base measurement, sizes are cross-referenced against published ISO 8653 circumference values and standard conversion tables to produce the UK, EU, Brazil, Japan, and Switzerland equivalents shown in your result.

Last updated: July 2026

Common Questions

Measure the inner diameter of the ring in millimeters, then use the conversion chart above. For example, a 17.3mm diameter corresponds to US size 7, UK size N½, EU size 54, and Brazil size 12. Alternatively, use the "Enter Measurement" method in the calculator to get instant conversions to all systems.
The paper strip method requires nothing but a piece of paper and a ruler. Cut a thin strip, wrap it around your finger, mark the overlap with a pen, then measure that length — that's your finger circumference. Enter it into the "Measure Your Finger at Home" method above (choose the "Paper Strip" option for step-by-step instructions) for an instant conversion. If you have an existing ring, you can also use the on-screen virtual sizer.
Not accurately. There is no reliable statistical relationship between height, weight, and ring size. Finger size is determined by bone structure, which varies independently of overall body size. Tall people can have small fingers; petite people can have larger fingers. The only accurate method is direct measurement of the finger or an existing ring.
US sizes use a numerical scale (1–13, with half sizes) based on finger circumference. UK sizes use letters (A–Z+6), also based on circumference. There's no simple formula to convert between them — you need a conversion table. A US 7 is a UK N½, a US 8 is a UK P, and so on. Use the chart above or the calculator to convert precisely.
For women, the most common ring size is US 6–7 (approximately 16.5–17.3mm diameter). For men, the most common range is US 9–10 (approximately 19–19.8mm). However, there is significant variation, and these averages shouldn't be used as a substitute for actual measurement — especially for an engagement ring or wedding band.
A virtual ring sizer lets you place an existing ring directly on your screen and resize a digital outline to match its inner opening. After you calibrate the display with a coin or standard card, the circle represents an estimated physical diameter. Because screen settings can affect accuracy, confirm the result before ordering a high-value ring.
In most cases, sizing up is the safer choice: a ring that's very slightly loose won't fall off in normal use and can be sized down by a jeweler for a modest fee, while one that's too tight is uncomfortable and more expensive to resize. That said, it depends on band width, knuckle size, and how you like a ring to fit — it isn't a universal rule. When in doubt, ask the retailer about their return and resize policy before purchasing.
Not always. They're usually worn on the same finger and sized to match, but band width differs between the two, so the numeric size that fits comfortably can shift slightly — it's worth trying them together before the wedding.
Yes — the on-screen method above works with any ring you can lay flat, whether it's yours or borrowed. Just measure the inner diameter, not the outside of the band.

Ring size estimates are for reference only. Actual fit depends on ring width, shape, and personal preference.

For high-value pieces, always visit a jeweler for a professional in-person sizing.

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