FAQ: ring size calculator and sizing questions

Short answers to the questions people actually ask about ring sizing, each linking to the page that covers it properly.

The quick reference

If your question is not here, the complete index of guides lists every page grouped by task.

Measuring

What is the most accurate way to measure at home?

Measuring a ring that already fits the same finger. You are measuring a rigid object, so there is no tension error and no temperature effect. A plastic strip sizer is a close second and has the advantage of testing whether the ring clears your knuckle. All four methods compared

Can I use string?

You can, but it is the least reliable common method and it fails in one direction: string stretches and cuts into the skin, so it reads small. Paper does neither and is almost always available. Why string underestimates

Should I measure the knuckle or the base of the finger?

Both, and size for the larger. The base determines how the ring sits day to day; the knuckle determines whether it can get there at all. Other measuring errors

When should I measure?

Late afternoon or early evening, at room temperature, on an ordinary day. Not first thing, not straight after exercise or a hot shower, not after coming in from the cold. The full protocol

Can I measure my ring size on my phone?

Only with a tool that first calibrates against something physical, usually a bank card. Screen sizes and pixel densities vary between devices, so an uncalibrated on-screen circle is an unknown physical size. What phones can and cannot do

Sizes and conversion

Which ring sizes are ordered most often?

US 6 and 7 for women, US 9 and 10 for men, with US 7 and US 10 the usual jeweller sample sizes. These describe the busiest part of a wide distribution, not a safe guess for a specific person.

Are men's and women's ring sizes different?

Not as a scale. A US 9 is a US 9 on anyone, because the size measures a finger rather than a person. Men simply tend to sit higher on the same scale, and men's bands tend to be wider — which does change the size needed. Men's sizing and band width

How much difference is there between one size and the next?

About 2.5 mm of inside circumference for a full US size, or about 0.8 mm of diameter. A half size is about 1.25 mm of circumference. One UK letter step is also about 1.25 mm, which is why a US size spans roughly two UK letters.

What is a US 7 in UK and EU sizes?

A UK N½ and an EU 54. All three describe a ring with a 17.3 mm inside diameter and a 54.4 mm inside circumference. How the systems relate

What does an EU size actually mean?

It is the inside circumference in millimetres. An EU 54 ring measures 54 mm around the inside — the size and the measurement are the same number. EU sizing explained

Is there a formula for converting US to UK sizes?

No. The two scales are historically unrelated, so a lookup table is always needed. The useful approximation is that one US size is about two UK letters. The US to UK chart

Fit

Should I size up or down if I am between sizes?

Up, in most cases, because the failure modes are not symmetrical. A loose ring can be worn today and sized down later; a ring that will not clear your knuckle cannot be worn at all. There are exceptions. The full decision

Do I need a bigger size for a wide band?

Generally yes, from about 6 mm of width. Most jewellers suggest half a size, and a full size above roughly 8 mm. Comfort-fit bands run looser and partly offset this. Width adjustments

How should a ring fit?

It should go over the knuckle with a little resistance and sit at the base without pinching or spinning constantly. Taking it off should involve a brief pause at the knuckle rather than a struggle. If it slips off when you point your hand down, it is too loose.

Why is my ring tight in the evening?

Because your fingers are larger then. Across an ordinary day the change is often around half a size, and heat, salt, exercise and flights all add to it. The physiology

Buying and resizing

Can any ring be resized?

No. Plain metal bands in gold, silver, platinum or palladium usually move a size or two either way. Full eternity bands, tension settings, and anything in tungsten, ceramic or titanium often cannot be resized at all. Which settings can be altered

How do I find someone's ring size without asking?

Borrow a ring they already wear on the target finger and measure it. This is the most reliable of the discreet methods, because you are measuring a fixed object. Failing that, ask a close friend, or have a jeweller size them during ordinary browsing. Methods ranked by reliability

Do ring sizes vary between jewellers?

Slightly. There is no enforced global standard for the US and UK scales, and published charts differ by up to roughly a quarter of a size between manufacturers. For anything expensive, use the retailer's own chart.

About this site

Where do the numbers on this site come from?

Every figure on every page is generated from one reference table, so no two pages can disagree. The US diameters are the standard published jewellers' figures; circumference is diameter multiplied by pi; UK letters are matched to their own published circumferences; and EU sizes are the circumference, because that is what ISO 8653 defines a size as. More about the site

How does the calculator work?

It reduces whatever you enter to a single circumference, then finds the nearest published size and its UK and EU equivalents. The conversion explained in full

Is the calculator free?

Yes, with no account required and no advertising on the site.

Does the site record my measurements?

When you press the calculate button, it records the measurement, the resulting size, and whether the two input fields agreed — no name, no email, nothing identifying you. Exactly what is recorded