Ring size

Canada uses the same numbered scale as the United States, and GIA's ring size chart prints a single column for "U.S. and Canada". Each whole size adds about 0.8 mm of inside diameter and about 2.5 mm of inside circumference. A quarter size adds roughly 0.6 to 0.7 mm of circumference, which is why quarter and half sizes exist.

If you know the inside circumference of a ring in millimetres, subtract 36.5 and divide by 2.55 to estimate the size. This rule matches the table below to within about a tenth of a size. Other countries use different scales, so check which system a chart uses before you convert. The ring size guide goes through measuring in more depth.

The best way to get the right fit is to have a jeweller determine the size, typically with a set of finger gauges in half-size steps. At home, borrow a ring that fits the right finger and have a jeweller measure it on a ring mandrel, press the ring into soap to make an impression, or trace the inside of the ring with a pencil on paper.

Avoid string or wrapped paper: string can stretch and paper is easily damaged. If you measure a ring yourself, take its inside diameter edge to edge in millimetres and match it to the chart; on an unusually wide band, read a mandrel at the centre of the band. A ring that you already wear on the same finger, with a similar band width, is the most reliable guide.

The ring also has to pass the knuckle, which is usually larger than the rest of the finger. A size taken only where the ring will sit may not go on at all.

Fingers are not a fixed size. They shrink in the cold and swell in the heat, and humidity and altitude can also make a finger swell or shrink, so a measurement taken on a winter day can differ from one taken in midsummer.

That matters in Canada. In cold weather rings can slide around, so a ring that fits in July may feel loose in January. Measure more than once, on different days, and not straight after coming in from the cold. Your hands also differ: for a right-handed person, the left ring finger is typically about half a size smaller than the right.

A good fit is snug without being uncomfortable, and the ring slides over the knuckle without falling off by accident.

Yes. Rings with wide shanks usually need to be a bit larger because they fit more snugly, and a band and engagement ring worn together that are wider than 4 or 5 mm need special consideration. A wide band covers more of the finger, so it feels tighter than a thin band of the same number.

This is the main reason a signet ring or a broad men's band can need a different size from a slim ring. A comfort fit band is a related option to ask about. If you are choosing a wedding band, try the actual width on, not only your usual size; see the wedding bands service and the wedding band collection.

Often, but not always. A size or two either way is usually possible. Stretching has limits, and larger changes need metal inserted into the shank. Rings made of titanium, cobalt, tungsten carbide or stainless steel cannot be resized, and neither can rings with stones all the way around, such as diamond eternity bands, without adding or removing gems. Pavé and channel settings can be difficult to resize, as can twisted bands.

Engraving is another factor, since jewellers must work around any engraving or marks inside the ring. So if a style is hard to resize, get the size right before you buy. For a ring made to order, such as a custom engagement ring, give the size at the start, and compare widths at a showroom.