How to Measure Your Ring Size at Home Accurately

Measuring your ring size at home is genuinely easy, but only if you measure the right thing in the right conditions. Jewellers size rings by the inside circumference of the band, expressed in millimetres. Every national size code — US 7, UK N, EU 54 — is just a label attached to that measurement.

The string or paper method

• Cut a strip of paper about 5 mm wide, or take a length of non-stretchy string.
• Wrap it snugly around the base of the finger you intend to wear the ring on.
• Mark the exact point where the end overlaps the strip.
• Lay the strip flat against a ruler and read the length in millimetres.
• That length is your inside circumference. Divide by 3.1416 for inside diameter.

A circumference of 54.4 mm equals a diameter of 17.3 mm, which is a US 7, a UK N and an EU 54. Enter either number into the converter on the home page and every other system fills in instantly.

Measuring an existing ring

If you already own a ring that fits the correct finger, measuring it is more reliable than measuring your finger. Place the ring on a ruler and measure straight across the inside edge, through the centre. That distance is the inside diameter. Measure twice and take the average, because a ring resting at a slight angle reads large.

Conditions that change the result

Fingers are not a fixed size. They swell in heat, after exercise, after salty food and late in the day. They shrink in cold weather and early in the morning. Measure in the late afternoon at normal room temperature, when your hands are neither cold nor swollen, and repeat the measurement on two or three different days.

Your dominant hand is usually a quarter to a half size larger than the other hand. Always measure the specific finger on the specific hand that will wear the ring.

Common mistakes

Pulling the string tight is the most frequent error, and it typically costs half a size. The strip should sit against the skin without compressing it, and it must be able to slide over the knuckle. If your knuckle is noticeably wider than the base of your finger, measure both and choose a size in between — closer to the knuckle measurement for a ring you take on and off often.

Very wide bands sit tighter than thin ones. For a band 6 mm wide or more, add a quarter to a half size to the result you measured.

When to see a jeweller

Home measurement is accurate to roughly a quarter size, which is fine for most purchases. For an expensive or non-resizable ring — eternity bands, tension settings, carved designs — spend ten minutes with a jeweller and a set of steel sizing rings. It costs nothing and removes all doubt.