How to Measure Ring Size at Home: String, Paper, or Your Screen, No Ring Sizer Needed

Three ways to measure at home

There are three main ways to measure ring size at home. All of them come down to measuring the inner circumference (the distance around the inside of the ring) or the inner diameter (the width of the hole) and converting it to a size.

The method we recommend most is measuring a ring you already find comfortable. It has already passed the real tests: it goes on, it clears your knuckle, and it doesn’t spin too much, so copying its inner diameter is the safest shortcut. If you don’t have such a ring, measure your finger directly with paper or string.

Method 1: Wrap paper or string around your finger

1. 1

   Prepare a strip of paper about 5 mm wide

   String works too, but avoid anything stretchy like yarn or elastic. A narrow strip cut from copy paper is plenty.

2. 2

   Wrap it once around where the ring will sit

   Wrap it near the base of the finger, where the ring will actually rest. Don’t pull it tight; leave enough slack that the paper can move slightly on your finger.

3. 3

   Mark where it overlaps

   Draw a thin line with a pen where the paper overlaps. A thick pen can throw things off by around 0.5 mm from the width of the line alone.

4. 4

   Measure to the mark and convert

   The length from the end of the paper to the mark is your inner circumference. Subtract 40 to get the Japanese size (for example, 51 mm → size 11).

If you have large knuckles, measure over the middle knuckle as well as at the base. If the knuckle is bigger, that’s the size to match, because the ring has to get past it to go on at all.

Method 2: Measure a ring’s inner diameter with a ruler

If you have a ring that fits, you can also measure the width of its hole (the inner diameter) with a ruler and multiply by 3.14 to get the inner circumference. Be warned, though: this method drifts more easily than you’d expect.

• One size is only about 0.32 mm of inner diameter, which a ruler marked in 1 mm steps can’t resolve
• Unless you look straight down at the ruler and ring edge, parallax can shift the reading by about 0.5 mm
• If you measure from the outer edge, the result grows by the thickness of the ring
• On a ring warped into an oval, or a comfort-fit ring whose inside is domed, the value changes depending on where you measure

With calipers, the inside jaws can measure to 0.1 mm, which is far more accurate. Without calipers, the screen method below lets you see much finer differences.

Method 3: Place a ring on the screen and match a circle

Here you show a circle on a phone or computer screen, lay the ring on it, and resize the circle until it lines up with the inner edge. Because you’re comparing them directly on screen, you can adjust more finely than with a ruler.

1. 1

   Calibrate the screen to real size

   Screen sizes vary by device, so 1 mm on screen isn’t really 1 mm until you calibrate. Hold a credit card (85.6 mm wide) or a Japanese 1 yen coin (20.0 mm across) against the screen, and adjust until the frame or circle lines up exactly.

2. 2

   Place the ring over the on-screen circle

   Set the ring down gently so you don’t scratch the screen. A ring with a stone sits more steadily if you lay it on its side.

3. 3

   Match the circle to the inner edge

   Use the slider or the +/− buttons to change the circle in 0.1 mm steps until the red circle is just hidden by the ring’s inner edge.

4. 4

   Read the result

   You’ll see the inner diameter, inner circumference, and Japanese size, along with US, UK, and EU sizes.

Calibration decides nearly all of the accuracy. Adjust little by little until the line sits on the right edge of the card, or on the whole rim of the coin. For calibration tips and what makes it drift, see Measuring Ring Size on a Screen.

Tips that keep any method on target

• Measure when your fingers are larger, such as in the evening or after a bath (they’re slimmer in the morning and on cold days)
• Measure two or three times on different days and go with the largest result
• Measure the finger and hand you’ll actually wear it on (right and left hands, ring and middle fingers all differ)
• If you’re buying a wide ring, go 0.5 to 1 size above what you measured

You’ll make fewer mistakes if you don’t simply order the size you measured, but also factor in band width and knuckle size. See What Size for a Wide Ring? for how much to add, and the Japanese Ring Size Chart for how sizes map to lengths.

FAQ

Can I measure ring size without a ring sizer?

Yes. You can wrap paper or string around your finger to measure the circumference, measure the inner diameter of a ring you own, or place a ring on a screen and match a circle to it. If you have a ring that fits, copying its inner diameter is the least likely to go wrong.

Is measuring with string accurate?

It gives a rough guide, but pulling too tight or the string digging in tends to make it read about half a size small. Use paper that doesn’t stretch, wrap with a little slack, and aim about half a size above the result.

Can I measure ring size on my phone screen?

Yes. Since screen sizes vary by device, you first hold a credit card or coin to the screen to calibrate it to real size. Then place the ring on the screen and match the circle to its inner edge to get the inner diameter and size.

Where exactly should I measure a ring’s inner diameter?

Measure the inside, not the outside: the longest distance from inner edge to inner edge (the diameter). On a ring with a domed inside, go by the narrowest point, because that’s the part that touches your finger.

When is the best time to measure my finger?

In the evening or on a warm day, when your fingers are larger. Fingers are slimmer in the morning and in the cold, and a ring sized then can feel tight when they swell. Measuring several times on different days and using the largest result is the safe choice.