Ring Size Chart: US, UK & EU Conversions and How to Measure

Ring size is one number that decides whether a ring gets worn or lives in a drawer. The chart below gives every US size with its exact internal diameter and circumference, converted to the UK, Australian, Irish and European systems. But the chart is the easy part — most sizing mistakes come from when and how you measured, not from reading the wrong row. Both are covered here.

The Full Ring Size Chart

US, UK/AU/IE and EU, with exact measurements.

Find the row that matches either the inside diameter of a ring you already own, or the measured circumference of your finger. Diameter is the distance straight across the inside of the band; circumference is the distance all the way around.

European conversions are approximate — the ISO system runs in whole millimeters of circumference, so it rarely lands exactly on a US half size. Where a conversion falls between two EU numbers we round to the nearer one.

How Big Is a Size 7 Ring?

The most-asked single question in ring sizing.

A US size 7 ring measures 17.3 mm (0.681 in) across the inside and 54.4 mm (2.14 in) around the inside. It converts to UK/Australian N½ and European 54.

Size 7 is worth knowing because it sits at the center of the women's range in the United States — it is the size most often ordered, and the size most stock rings are made in. For scale: a size 6 is 0.8 mm smaller in diameter, a size 8 is 0.8 mm larger. That is the whole difference between one full size and the next. Ring sizing is a game of fractions of a millimeter, which is exactly why casual measuring methods fail.

How the Sizing Systems Actually Work

Three systems, three different logics.

• United States, Canada and Mexico use a numeric scale in quarter-size steps. Each whole size step adds exactly 0.032 inches (0.81 mm) to the internal diameter. The numbers are arbitrary — a "size 7" is not 7 of anything.
• United Kingdom, Australia and Ireland share an alphabetical scale running A to Z, then Z+1, Z+2 and onward, with half sizes marked ½. One letter is roughly half a US size, which is why UK conversions so often land on a half.
• Continental Europe largely follows ISO 8653:2016, which defines ring size as the internal circumference in millimeters. It is the most logical of the three: a size 54 ring is 54 mm around. It is used across Austria, France, Belgium and the Nordic countries among others.

Because these systems were built independently, conversions between them are never perfectly clean. When you order internationally, give the millimeter measurement alongside the size number — millimeters are unambiguous and every jeweler can work from them.

How to Measure Your Ring Size at Home

Four methods, ranked by how much you can trust them.

1. A physical ring sizer (most accurate). A plastic or metal sizer costs very little and removes all guesswork, because you are testing the actual fit rather than calculating it. If you are buying an engagement ring or anything that cannot be resized, this is the only method we genuinely recommend — you can order a ring sizer here.
2. A printable paper sizer (very good). Print at 100% / Actual Size with scaling turned off, then verify the printed ruler measures exactly 80 mm before you use it. Then either lay a ring you own over the printed circles until one matches the inside edge, or cut out the finger strip, wrap it around your finger and thread the end through the slit. Our printable ring sizer is free to download.
3. Measuring a ring you own (good). Use a ruler with a millimeter scale to measure straight across the inside of the band, then match that diameter in the chart above. Measure the inside edge to inside edge, not the outside — including the metal will read a full size too large.
4. String or paper strip around the finger (unreliable). This is the method everyone reaches for and it is the one that most often produces the wrong answer. String stretches, tape distorts, and how tightly you pull changes the result by a full size or more. If it is all you have, wrap it snugly rather than tightly, mark the overlap, measure the length in millimeters, and use the circumference column — then treat it as an estimate.

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Can Your Phone Measure Your Ring Size?

Yes — with one important caveat.

On-screen ring sizers work by scaling the display against an object of known size, then showing you a circle at true scale. They can be genuinely accurate, but everything depends on the calibration step. If the reference object is off by two millimeters, your ring size is off by two sizes.

• On a phone, calibrate with a coin. A bank card is 85.6 mm long, which is wider than many phone screens — so it cannot be displayed at full scale and the calibration fails. A US quarter (24.26 mm), a £1 coin (22.5 mm) or a €1 coin (23.25 mm) all fit comfortably.
• On a laptop or desktop, a bank card works well — hold it against the outline and drag until the widths match exactly.
• Check your zoom level is 100% before you start, and do not zoom during the process.
• Treat the result as a close guide, not a guarantee. For an engagement ring or any ring that cannot be resized, confirm with a physical sizer.

Our ring sizer tool includes a calibrated on-screen dial with coin and card references, a printable sizer, and the full conversion chart in one place.

When to Measure — Timing Changes the Answer

The most overlooked variable in ring sizing.

Your fingers are not a fixed size. They can vary by close to a full ring size across a single day, and most badly fitting rings were measured at the wrong moment rather than measured incorrectly.

The practical rule: measure two or three times, on different days, in the late afternoon at room temperature, and take the size that comes up most often. If you get two different answers, choose the larger.

Six Mistakes That Produce the Wrong Size

Every one of these is common.

• Measuring the outside of a ring instead of the inside. The band's own thickness adds a full size or more.
• Measuring the wrong finger. Your dominant hand is usually a quarter to a half size larger than the other. Measure the exact finger the ring will live on.
• Pulling the string tight. A ring has to slide over a knuckle; a tourniquet measurement will never fit.
• Printing a sizer at "fit to page." Any scaling silently invalidates the whole chart. Always confirm the printed ruler measures 80 mm.
• Sizing from an old ring that never fit well. If the ring you are copying spins or sticks, you are copying a mistake.
• Ignoring band width. Covered below — it is worth up to a half size.

When Your Knuckle Is Bigger Than Your Finger

A real fitting problem with real solutions.

If your knuckle is significantly larger than the base of your finger, no single number is right: a ring that passes the knuckle will spin at the base, and a ring that sits snugly at the base will not go on.

1. Measure both. Take the knuckle measurement and the base measurement separately.
2. Choose between them, closer to the knuckle. The ring must be able to get on and off. Aim for the smallest size that still passes the knuckle without a fight.
3. Ask about sizing beads. Two small beads added inside the band hold the ring centered at the base while still letting it slide over the knuckle. This is the standard fix and it works well.
4. Consider a hinged or adjustable shank for a large difference — more involved, but it solves the problem completely.
5. Avoid heavy top-weighted designs if the ring will be loose at the base, since they spin faster. A bezel setting or a balanced solitaire sits more evenly.

Wide Bands Need a Bigger Size

The single most useful rule in this guide.

A wide band covers more of your finger, grips more skin, and feels distinctly tighter than a thin band of the identical size. This catches out almost everyone buying a men's band or a wide stacking ring.

Two consequences worth planning for. First, a wide band and a thin band worn on the same finger may genuinely need different sizes — that is normal, not an error. Second, comfort-fit bands (domed on the inside) usually run slightly larger than standard-fit, so you may need to come back down a quarter size. Our men's wedding band width guide covers choosing a width in detail.

Average Ring Sizes

Useful for a starting point — dangerous as a substitute for measuring.

In the United States, the most commonly ordered women's ring sizes are 6 to 6.5, and the most common men's sizes are 9 to 10. Across the full range, women's rings typically fall between size 4 and 9, and men's between size 8 and 14.

Treat these as the middle of a very wide distribution rather than a prediction. Hand size correlates poorly with height or build, and buying for someone else on an average alone is how rings end up unworn. Averages are for narrowing a guess when you truly cannot measure — see the secret-sizing methods below before you fall back on one.

How to Size Secretly for a Proposal

Five methods that do not give the surprise away.

1. Borrow a ring they already wear. The best option by far. Take one they wear on the correct finger, measure the inside diameter with a millimeter ruler, and return it the same day. If you cannot measure it, press it into a bar of soap or modeling clay and measure the impression.
2. Ask someone who can ask. A sibling, a best friend, or a parent can usually raise ring size in conversation without suspicion. This is the most accurate indirect route.
3. Trace around a ring on paper. Trace the inside edge as precisely as you can, then measure across the traced circle. Less accurate than a direct measurement, but workable.
4. Use a costume ring as a decoy. Give an inexpensive ring as a gift and see which finger it fits, then size from that.
5. Design something resizable. If sizing is genuinely impossible, choose a classic solitaire or a simple gold or silver band that can be adjusted afterward — and avoid eternity bands and tungsten. You can also build a custom ring and finalize sizing later.

If you are still deciding on the ring itself, our guides to engagement ring styles and settings, how much to spend, and which hand the ring goes on cover the rest of the decision.

What If You're Between Two Sizes?

Size up. Here is why.

If you measure consistently between two sizes — say between a 6.5 and a 7 — take the larger one. The reasoning is asymmetric: a slightly loose ring can be padded, beaded, or resized down, and it still gets worn in the meantime. A ring that is genuinely too tight cannot be worn at all, is uncomfortable in hot weather, and in the worst case has to be cut off.

Size up in particular when the band is wide, when the wearer's hands swell in heat or after exercise, when the ring is for a finger with a prominent knuckle, and when the ring will be worn every single day. Stay with the smaller size only for a thin band on a finger with a small, smooth knuckle — or for a ring that will mostly be worn occasionally.

Which Rings Can Be Resized — and Which Can't

Get this right before you order.

This is where sizing stops being a preference and becomes a decision, because some materials cannot be altered at all.

If you are choosing a tungsten or titanium band, sizing accuracy is not optional — use a physical sizer. Our guides on whether tungsten rings can be resized and titanium versus tungsten explain the metallurgy, and whether tungsten scratches covers daily wear.

For precious metals, the karat matters less for resizing than the design does — see our 10K vs 14K vs 18K guide. Keeping a ring fitting well over time is mostly a matter of care; our engagement ring care guide covers checking the setting and shank annually.

Technical references for the sizing systems in this guide: the documented international ring size standards including ISO 8653:2016 and the general reference on rings as jewelry.

Ring Size FAQ