Home / How to measure ring size
How to measure ring size at home
All you need is a strip of paper, a pen and a millimetre ruler. Five minutes, and you'll have a number you can order with.
Method 1: the paper strip (most reliable at home)
- Cut a strip of paper about 1 cm wide and 10 cm long. Paper doesn't stretch, which makes it better than string.
- Wrap it around the base of the finger the ring is for. It should be snug but able to slide over the knuckle with a little resistance.
- Mark the point where the paper overlaps with a fine pen.
- Lay the strip flat against a ruler and read the length from the end to the mark in millimetres.
- Type the number into the ring size calculator. Repeat twice more and use the largest result if they differ.
Method 2: string or thread
Same steps, but use unwaxed dental floss or non-stretch thread, and wrap it once, flat, without twisting. Pinch the crossing point before you pull it off, because string loses its mark easily. String measurements often read small because people pull them tight; err toward the looser reading.
Method 3: measure a ring that already fits
Lay the ring on a ruler and measure the inside diameter, edge to edge through the centre. Or place it on the online ring sizer and match it to a circle after calibrating your screen. Choose a ring worn on the same finger; a pinky ring won't tell you much about your ring finger.
Unroll the ring: why a strip of paper works
A ring size is really a length. Drag the slider to unroll the band flat: the strip you get is exactly π (about 3.14) times the inside diameter. That is why wrapping paper around your finger and measuring it gives the same answer as measuring a ring across.
US 7: diameter 17.32 mm × π = 54.4 mm around, which is EU 54 and UK N½.
Each US size adds 0.81 mm across but 2.55 mm around. A 1 mm slip in a paper-strip measurement is less than half a size; a 1 mm slip measuring a ring across is more than a full size. Measure diameters carefully.
Mistakes that give the wrong size
- Measuring cold hands. Fingers can shrink by a size in cold weather. Measure warm, at room temperature.
- Ignoring the knuckle. If your knuckle is much larger than the base of the finger, measure both and choose a size between the two, closer to the knuckle.
- Forgetting the band width. Bands 6 mm and wider feel tighter; size up by about half a size. See how a ring should fit.
- Printing a sizer at the wrong scale. "Fit to page" shrinks it. Print at 100% and check the ruler on the printable ring sizer.
When to see a jeweler instead
For an expensive ring, a ring that can't easily be resized (eternity bands, tension settings, some tungsten and titanium), or if your measurements keep disagreeing, a jeweler's metal sizing rings take a minute and are usually free. Try the size on at the end of the day.
Pleasingly, the whole trick of the paper strip is a bit of geometry older than any jeweler: circumference is π times diameter. Circles in the sky hide their geometry better. The Moon is a full sphere all month long, and ahaboo walks you through why we only see a slice of it.
Questions people ask
How can I measure my ring size at home without a ring?
Cut a thin strip of paper about 1 cm wide, wrap it snugly around the base of the finger, mark where it overlaps, and measure the length in millimetres with a ruler. Enter that number into the ring size calculator. String works too, but it stretches, so pull it gently.
Which finger and hand should I measure?
Measure the exact finger the ring will be worn on. Left and right hands usually differ, and the dominant hand is often slightly larger.
What time of day is best to measure?
Late afternoon or evening at normal room temperature. Fingers are smaller in the morning and when cold, and larger after exercise, in heat, or after salty food.
How do I measure a ring I already have?
Measure the inside diameter straight across the widest part of the opening, inside edge to inside edge, in millimetres. Enter it in the calculator under "A ring that fits". A 1 mm error across is more than one full US size, so use a ruler with clear millimetre marks.
Is the string method accurate?
It is usually within about half a size if done carefully. The common errors are measuring too loosely, using stretchy string, and forgetting that the ring has to pass the knuckle.