Ring size guide

Find your ring size

Half a size off is the difference between a ring that sits right and one that spins, pinches, or won’t get over the knuckle. And most rings our makers build, in tungsten, ceramic, titanium or carbon fiber, can’t be resized afterward. So it pays to get it right the first time.

Here’s how sizing actually works, every way people have tried to do it at home, and the two ways we trust: get close with your phone, then confirm with a ring sizer on your finger.

4 5 6 7 8 9 10 11 12 13
US sizes 4 to 13, drawn in proportion. One full size adds 0.81 mm across the inside.

  • Get close in a minute

    Use your phone and any bank card. Usually within 1 ring size.

    Try the phone sizer →

  • Know for sure

    SureFit comfort-fit sizers, in the width you’ll actually wear.

    Shop ring sizers →

  • Sizing someone else?

    A customer across the country, or a partner who can’t know you’re asking.

    Here’s how →

The basics

How a jeweler sizes a finger

Walk into a jewelry store and they’ll hand you a ring of sizing rings: metal bands, one for every half size. You try them until one slides over your knuckle with a little resistance and sits at the base of your finger without spinning. That’s your size. It’s still the best method there is, because you’re testing a real ring on a real finger.

US sizes measure the inside of the band. Each full size adds 0.81 mm across the inside, which is 2.55 mm around your finger, about a tenth of an inch. That’s all it takes to go from snug to sliding off.

18.95 mm across the inside = US size 9 59.5 mm around the inside
A ring size is the inside of the band. Size 9 is 18.95 mm across and 59.5 mm around.

Three things change the answer

  • Width. A wide band covers more of your finger, so an 8 mm ring often feels tighter than a 4 mm ring in the same size. Size with the width you’ll wear.
  • Fit. A comfort fit profile is domed on the inside; a standard fit profile is flat. The same size in each often fits at least half a ring size differently. Most jewelers’ sizing rings are standard fit.
  • Timing. Fingers swell in the heat and after a workout, and shrink in the cold. Measure at the end of the day, at room temperature, and more than once. Better yet, wear a sizer for a day.
Standard fit profile flat inside Comfort fit profile domed inside
Cut through the band: the standard fit profile is flat inside, the comfort fit profile is domed. Same size, often at least half a ring size apart in fit.

At home

Every way people have tried to do it themselves

Not everyone lives near a jeweler, and nobody wants to ask their partner for their ring size. So people have come up with plenty of ways to measure at home. Here they are, from the oldest trick to the newest. Most share one problem: a full size is only 2.55 mm around the finger, and that’s an easy amount to lose.

  1. String or dental floss

    Often a size off

    Wrap it around the base of your finger, mark where it overlaps, and measure the length with a ruler.

    The catch: String stretches, floss flattens, and a pen mark is hard to place within a millimeter. It measures the base of the finger and ignores the knuckle.

  2. A strip of paper

    Hit or miss

    The same idea, with something that doesn’t stretch.

    The catch: Paper is flat and stiff, so it gaps or creases around a round finger. Still nothing for the knuckle.

  3. Measuring a ring that fits

    Close with calipers

    Borrow a ring that already fits and measure straight across the inside, or trace the inside edge on paper.

    The catch: A pencil line is thicker than the difference between two half sizes, and the ring may be from a different finger. With calipers, it’s good.

  4. Printable ring sizers

    Hit or miss

    Print a paper sizer or a chart of circles at home.

    The catch: It’s only right if it prints at exactly 100%. Most printers default to fit-to-page, which quietly shrinks it.

  5. Plastic multi-sizers

    Close

    A plastic strip marked in sizes that loops through itself like a zip tie.

    The catch: Cheap and fairly close, but it’s thin and flexible, nothing like a wide band on your finger.

  6. Circles on a screen

    Hit or miss

    Hold a ring over circles on a website or in an app until one matches the inside edge.

    The catch: Every screen has a different pixel density, so those circles are only true size if the site knows your exact screen. Most don’t, and most don’t ask.

  7. A phone that measures your finger

    Within 1 ring size

    Our phone sizer measures your screen with a bank card first, then measures your finger on it.

    The catch: It gets you close, not exact. That’s what ring sizers are for.

The final say

The sure way: a sizer on your finger

Sizing rings work because you’re wearing a ring. The catch is that most sets are thin bands with a standard fit profile, and the rings our makers build are often wide with a comfort fit profile. That alone can put you half a ring size off. So we made sizers that match.

SureFit sizers are comfort fit and come in 4, 6, 8 and 10 mm widths. Wear the width you’re buying, and the size that fits is the size you order.

A minute at the jewelry counter is a snapshot. Your finger changes through the day, and sliding sizing ring after sizing ring over your knuckle can swell it on the spot. Get sized while it’s swollen, and by the time the ring arrives your finger is back to normal and the ring spins.

A SureFit single wears like a regular ring, for as long as you like: a morning, a workout, a hot afternoon, a cold night. If it’s comfortable through all of it, that’s your size.

New

The new way: get close with your phone

Every on-screen sizer has the same flaw: it doesn’t know how big your screen really is. Ours measures that first.

  1. Measure your screen. Lay any bank card, ID or gift card on the green strip and match the strip to the card. Those cards are all 53.98 mm wide, so now the sizer knows your screen’s real scale. Your phone remembers it for next time.
  2. Measure your finger. Rest your finger on the strip and step through the sizes until the edges just touch the widest part of your finger.
  3. Confirm it. You’ll get a size, usually within 1 ring size of your true size. Order SureFit sizers around it and let them have the final say before you order a ring that can’t be resized.

Try it now

Grab a card. It takes about a minute.

Sizing someone else

Your customer’s size, or your partner’s

Your customer’s

If you sell rings, don’t guess, and don’t ask your customer to wrap string around their finger. Send them sizers. Our Direct to Client sizers ship five consecutive sizes straight to your customer anywhere in the US, with your business name on the instructions.

Not sure which five? Send them this page first. The phone sizer gets them close, and the sizers settle it.

Your partner’s, quietly

Borrow a ring they already wear on the right finger. For an engagement or wedding ring, that’s the ring finger of the hand they’ll wear it on. Measure straight across the inside at the widest point and find the number in the chart below. Calipers are best; a ruler gets you in the neighborhood.

No ring to borrow? Ask someone they’d tell: a parent, a sibling, the friend who’s already been ring shopping with them.

Reference

Ring size chart

Inside diameter is the number that matters. Measure straight across the inside of a ring that fits, at the widest point, and find the closest number.

Inside circumference is here for anyone who measured around their finger with string or paper, and because much of Europe uses it as the size. Both are measured on the inside of the band, so the band’s thickness doesn’t change them.

US sizeInside diameterInside circumference
4 14.88 mm 46.8 mm
4½ 15.29 mm 48.0 mm
5 15.70 mm 49.3 mm
5½ 16.10 mm 50.6 mm
6 16.51 mm 51.9 mm
6½ 16.92 mm 53.1 mm
7 17.32 mm 54.4 mm
7½ 17.73 mm 55.7 mm
8 18.14 mm 57.0 mm
8½ 18.54 mm 58.3 mm
9 18.95 mm 59.5 mm
9½ 19.35 mm 60.8 mm
US sizeInside diameterInside circumference
10 19.76 mm 62.1 mm
10½ 20.17 mm 63.4 mm
11 20.57 mm 64.6 mm
11½ 20.98 mm 65.9 mm
12 21.39 mm 67.2 mm
12½ 21.79 mm 68.5 mm
13 22.20 mm 69.7 mm
13½ 22.61 mm 71.0 mm
14 23.01 mm 72.3 mm
14½ 23.42 mm 73.6 mm
15 23.83 mm 74.8 mm

From the US standard: inside diameter = 11.63 mm + 0.81 mm per size. Use the phone sizer above and your result is highlighted here.

Questions

I’m between two sizes. Which one?

Wear each one for a day on a SureFit sizer in the width you’re buying. If you can’t, the larger is usually the safer pick: a ring that’s a touch loose can be worn, and one that won’t pass the knuckle can’t.

Does the width of the ring change my size?

It can. Wider bands usually feel tighter. Size with the width you’ll wear, which is why SureFit comes in four widths.

Can my ring be resized later?

Tungsten, ceramic, titanium and carbon fiber rings generally can’t be resized the way gold can. That’s why we push so hard on getting the size right before the ring is made.

Which hand should I measure?

The one you’ll wear it on. For many people the dominant hand runs a little bigger.

How accurate is the phone sizer?

Usually within 1 ring size. It’s built to get you close, so the sizers you order cover the right range. SureFit sizers have the final say.

Are ring sizes the same everywhere?

No. The US and Canada use numbers, the UK and Australia use letters, and much of Europe uses the inside circumference in millimeters. This guide uses US sizes.

Get it right the first time

Get close with your phone, confirm with a SureFit sizer, then order the ring.

Shop ring sizersTry the phone sizer