How to check your ring size at home

No sizer, no jeweller, no appointment. Here is what actually works with what is already in the kitchen drawer, and how far you can trust each method.

Published 2026-10-23

A ring size is one number: how far it is round the inside of the band, in millimetres. US size 7 is 54.4 mm round; US 6 is 51.9 mm. Everything below is a different way of getting at that number, and the whole job is to get within about a millimetre of it.

A millimetre sounds like nothing until you see what it buys. One whole US size is 2.55 mm of circumference. A half size — the step shops actually stock — is 1.28 mm. A Japanese 号 is 1.05 mm. So "within a millimetre" means "within about a third of a size", which is close enough to order with confidence.

Method 1: a strip of paper (best without a printer)

Paper beats string, and it beats thread by a wide margin. String stretches when you pull it taut to read the mark, and thin thread cuts into the skin and reads small. A strip of paper does neither.

1. Cut a strip about 5 mm wide and 100 mm long from an envelope, a receipt or any paper that is not flimsy.
2. Wrap it round the base of the finger. Snug: you should feel it there, but it must still slide over the knuckle without a fight.
3. Mark the overlap with a fine pen. Put the mark exactly on the edge of the overlapping end, not somewhere near it.
4. Unwrap and measure from the end of the strip to the mark, in millimetres.
5. Type that number into the ring size calculator as the circumference.

Do it twice, an hour apart. Two readings within a millimetre of each other mean you have your answer. Two readings three millimetres apart mean the strip was pulled tighter the second time — do it a third time and take the loosest of the three that still felt snug.

Accuracy: about ±1 mm with care, which is a third of a size. Good enough for almost any purchase.

Method 2: a ring you already wear (best of all, if you have one)

A ring that already fits has been sized properly by somebody with a steel mandrel. Measuring it is easier and more reliable than measuring a finger, because a ring does not swell in the heat or shrink in the cold.

Lay the ring flat on a table and measure straight across the inside, at the widest point, with a ruler. That is the inside diameter. Type it into the calculator, or multiply by 3.1416 to get the circumference yourself.

The mistake everyone makes here is measuring the outside. On a 6 mm band the outside diameter is more than a full size bigger than the inside. If the ruler reads across the metal as well as the hole, you will order a ring that will not go on.

Better than a ruler: match the ring to a circle on your screen. Calibrate the screen with a bank card first — every card is ISO/IEC 7810 ID-1, exactly 85.6 × 53.98 mm — and then the screen is a ruler with marks every tenth of a millimetre.

Accuracy: ±0.3 mm on screen, ±0.5 mm with a ruler. Better than any finger measurement — but it only tells you about the finger that ring is worn on.

Method 3: dental floss or a shoelace

If there is no paper, floss is the next best thing: it does not stretch much and it is thick enough not to cut in. Wrap, mark with a pen, unwrap, measure against a ruler.

Avoid sewing thread, hair elastics and rubber bands. Thread reads small because it sinks into the skin; anything elastic reads whatever you want it to read.

Accuracy: about ±1.5 mm, or half a size. Fine for a gift you can exchange; thin for an engagement ring.

Method 4: the soap impression

This is the one for a surprise. Press a ring the person already wears flat into a bar of soap, a lump of modelling clay or a piece of Blu Tack until it leaves a clean ring-shaped groove. Lift the ring out carefully and measure across the inside of the impression.

It works because you can do it in thirty seconds with a borrowed ring and give the ring straight back. It is less accurate than measuring the ring itself, because the soap deforms, so round down rather than up if you are between two readings — and read the rest of [finding a size without asking](/blog/ring-size-without-her-knowing/) before you rely on it.

Accuracy: about ±1 mm, if the impression is clean.

Method 5: print a paper ring sizer

This is the closest thing at home to the steel sizer in a shop — a strip with a slot you feed the tail through, exactly like the plastic ones jewellers hand out. Print one here; it takes one sheet of ordinary paper.

The catch is printing. Browsers and print drivers shrink pages by a few per cent to stay clear of the printer's unprintable margin, and nothing on the page tells you it happened. A sizer printed at 96 % reads a size and a half small.

That is why every sheet of ours carries a 50 mm line and a bank-card outline. Measure the line with a real ruler; lay a card on the outline. If either is out, the sheet printed at the wrong scale and you should fix the setting before you cut anything.

What a US 7 finger measures on a sheet printed at the wrong scale.

Accuracy: ±0.5 mm if the scale checks out, and badly wrong if it does not. Always check.

The four things that make all of these wrong

• Time of day. Fingers hold more fluid as the day goes on. Morning to evening is often half a size and can be a whole one. Measure in the evening.
• Temperature. Cold hands read small — come in from the cold and wait ten minutes. Hot hands, a salty meal, a long flight or a hard workout all read large.
• The wrong hand. The same finger on the dominant hand is usually a quarter to a half size larger than on the other. Measure the hand that will wear the ring.
• The knuckle. If the knuckle is the widest part of the finger, the ring has to pass it. Measure the knuckle as well and order the larger of the two; then ask the jeweller for sizing beads so it does not spin at the base.

Which size do I actually order?

Take the largest sensible reading you got. If it falls between two half sizes, go up — read [what to do between sizes](/blog/between-ring-sizes/) for why. If the band is 4 mm wide add a quarter size, and if it is 6 mm or wider add a half: a wide band wraps more of the finger and sits tighter at the same measurement.

The common sizes, for reference

Jewellers stock women's rings from about US 5 to 7 and men's from about US 8 to 10.5. If your measurement lands far outside those, measure again before you order — it is more often a mistake than an unusual finger.

Computed from the definition of each system — see the notes under the full chart.

When to stop measuring at home

Home measuring gets you to the right size or the one next to it. For most rings that is fine, because most rings can be sized afterwards for a modest fee.

It is not fine for rings that cannot be sized: eternity bands set all the way round, tension settings, tungsten carbide, ceramic and titanium. For those, spend ten minutes in a shop and have the finger measured on a steel mandrel. It costs nothing and removes the only part of the purchase you cannot undo.