How to Know Your Ring Size Before Buying Online (4 Methods That Actually Work)

The most accurate way to find your ring size at home is to measure the inside diameter of a ring you already wear on that finger and match it to a size chart. The string-around-the-finger method everyone recommends is the least accurate and is why so many online rings come back for resizing.

Here's every method ranked by how well it works, a size chart, what to do if it's a surprise, and the rings you must get right the first time because they can't be resized.

How Do You Measure Ring Size at Home? Four Methods, Ranked

1. Measure a ring you already own (most accurate)

Take a ring you wear on the finger in question. Lay it on a ruler or, better, use a digital caliper if you have one. Measure the inside diameter in millimeters, edge to edge at the widest point. Match it to the chart below. This works because it measures a ring that already fits, not your finger, and fingers change size during the day.

If you don't have a ruler with millimeters, print one. Set your printer to 100 percent scale (not "fit to page") and check it against a credit card, which is 85.6 mm wide.

2. Use a plastic ring sizer (very accurate)

A plastic ring sizer is a belt-style loop that tightens around the finger and reads the size. They cost a few dollars online, or ask for one at a jeweler. Put it on at the end of the day when fingers are largest, make sure it slides over the knuckle with slight resistance, and read the number.

3. Trace the inside of a ring (reasonably accurate)

If you can't measure a ring, place it on paper and trace the inside circle with a sharp pencil. Measure the circle's diameter. Less precise than a caliper because the pencil line adds width, so round down half a size if you're between.

4. The string or paper strip method (least accurate)

Wrap string or a paper strip around the base of the finger, mark where it overlaps, measure the length. This gives circumference, which you then convert. The problem is string stretches, paper doesn't conform to the finger, and nobody pulls it to the same tension a ring has. In our experience this method is often off by half a size or more. Use it only as a last resort, and round up.

US Ring Size Chart (With UK and EU Conversions)

The average women's ring size in the US is 6 to 7. The average men's size is 9 to 10. If you're guessing for a woman and have no information, 6.5 is the most common size.

What Changes Your Ring Size?

• Temperature. Cold shrinks fingers by up to half a size. Heat and humidity swell them. Don't measure right after being outside in winter or after a workout.
• Knuckles. If your knuckle is noticeably larger than the base of your finger, size for the knuckle. A ring that slides over the knuckle with slight resistance and then sits a little loose at the base is correct. One that's snug at the base won't go on.
• Band width. Wide bands (6 mm and up) fit tighter than thin ones because they cover more finger. Go up a quarter to half size for a wide band. This matters most for men's wedding bands and eternity bands.
• Dominant hand. Your dominant hand is usually a quarter to half size larger. Measure the hand the ring will be worn on.

How Do You Find Her Ring Size for a Surprise Engagement Ring?

This is the question we get most. Five approaches, in order of how well they work.

1. Borrow a ring she wears on her left ring finger. Bring it to us or measure it with the chart above. This is the gold standard. If she only wears rings on other fingers, the right ring finger is usually within half a size of the left.
2. Ask her mother, sister, or best friend. One of them often knows, or can find out without raising suspicion.
3. Trace a ring she owns. If you can get a ring for two minutes, trace the inside on paper and bring us the paper.
4. Press a ring into a bar of soap. Old trick, still works. Press it in, pull it out, measure the impression.
5. Guess 6.5 and plan to resize. If all else fails, buy a 6.5 in a resizable setting. Most solitaires can go up or down two sizes.

One thing to avoid: don't propose with a ring that's obviously too small. Too big slides on and feels fine for the photo. Too small doesn't go on at all. If in doubt, size up.

Which Rings Can't Be Resized?

• Full eternity bands. Diamonds all the way around means there's no plain metal to cut and stretch. If the size is wrong, the ring has to be remade. Get it exact or choose a half eternity, which has a plain section and can be resized. See our lab diamond bands, which come in both.
• Tension settings. The stone is held by the pressure of the band. Resizing changes the pressure and risks the stone.
• Heavily pavé or channel-set bands. Can sometimes go a half size, but the small stones can loosen.
• Titanium and tungsten. Can't be cut. Must be exchanged.
• Rings with patterns or engraving all the way around. Resizing breaks the pattern.

Rings that resize easily: plain bands, solitaires, halos with a plain shank, most three-stone rings. 

Buying a Ring From Avianne & Co.

Every ring on our site lists available sizes, most in half sizes from 4 to 12. If your size isn't listed, ask; we can usually make it. If the ring arrives and doesn't fit, we can resize it, and returns are 14 days. 

Frequently Asked Questions

What is the average ring size for a woman?

Size 6 to 7 in the US. 6.5 is the most common size. For men it's 9 to 10.

How do I measure my ring size with a ruler?

Measure the inside diameter of a ring that fits, in millimeters, and match it to a chart. 16.5 mm is a size 6, 17.3 mm is a size 7, 18.1 mm is a size 8.

Is it better to size up or down?

Up. A slightly loose ring can be worn and resized later. A ring that's too small can't be put on. If you're between sizes, go to the larger one, especially for wide bands.

Can every ring be resized?

No. Full eternity bands, tension settings, and tungsten or titanium rings can't be resized. Plain bands and solitaires can usually go up or down two sizes.

Does ring size change with weight?

Yes. A 10 to 15 pound change usually moves ring size by about half a size. Pregnancy and age also change finger size, which is why many people have rings resized every decade or so.