How to read clothing size labels

An 'M' on the label is not a fixed size

Brands decide their own size labels, so the same 'M' can differ widely in actual measurements. It is common for one brand's M to be larger than another's L, and even within one brand, regular-fit and oversized lines are cut differently. National systems differ too: Korea uses numbers based on chest circumference, while Europe, the US and Japan each use their own numbers or letters. Choosing by the label alone leads to mistakes; the measurement table on the product page is the only reliable guide. If there is no table, ask the seller or skip it.

Body measurements and garment measurements differ

Size charts come in two kinds. One is a body chart saying which chest size a given size is meant for; the other is a garment chart measured from the item laid flat. A body chart is a recommendation with the brand's idea of ease already built in, so treat it as a reference; a garment chart gives the real size of the item and can be compared directly with your own clothes. Note that the chest figure on garment charts is usually measured straight across under the arms, which is half the circumference. Check which one you are looking at first.

What to measure

You do not need to measure everything. For tops, shoulder width and chest are what decide fit; for trousers, waist and rise are what matter. Length is easy to alter, whereas shoulders and waist are hard to fix, which makes the priorities clear. For dropped-shoulder designs, chest width and sleeve length are more useful than shoulder width. With trousers, a short rise is uncomfortable when sitting even if the waist fits, and tightness at the hip and thigh is felt all day, so check those two right after the waist.

• Tops: shoulder width, chest, body length, sleeve length
• Trousers: waist, hip, rise, length, hem width
• Length can be altered; shoulders and waist are hard
• Measure your own garment laid flat and compare

Use a garment that fits as your reference

Rather than measuring your body, laying a well-fitting garment flat and using its numbers as the baseline leads to fewer mistakes. Each garment includes a different amount of ease, so body measurements alone do not tell you how a finished piece will fit. Writing down reference numbers for the categories you buy most often saves time later. As a rough feel, a difference of one or two centimetres is barely noticeable, while three centimetres or more at the chest or waist is clearly felt when worn.

Fabric changes the fit

At the same measurements, stretchy fabrics feel roomier and stiff fabrics fit exactly as measured. With stretchy knits you can size slightly down; with low-stretch fabrics such as denim, follow the measurements precisely. Shrinkage after washing also varies by fabric: all-cotton T-shirts and raw denim should be expected to shrink a little after the first wash. Conversely, stretch trousers loosen slightly with wear, so a snug fit at first tends to last longer.

Extra care when ordering from abroad

The same number means different things in different national systems, so you cannot substitute one for another. Shoes differ the most, and sizing varies by brand even within one country's scale. Overseas sites often list measurements in inches, so convert using 2.54 cm to the inch, and some brands sell separate Asian and standard fits. Returns are often expensive, so check the measurements and look at reviews to see which size people with a similar build chose.

A pre-order checklist

The most effective way to reduce failed online orders is to check things in the same order every time. Think of the size name as the last thing you look at. The exchange and return policy is what should tip the decision when you are unsure, and if returns are difficult, not buying an item you are unsure about is a reasonable choice. Sizing within the same line of a brand that has fitted you before rarely changes much, so keeping a note of brands and sizes that worked makes the next purchase easier.

• Is there a garment chart, and is chest flat width or circumference
• Compare shoulders and chest (or waist and rise) with your reference garment
• Allow for stretch and washing shrinkage
• Check which size reviewers of similar height and weight chose
• Check exchange and return terms and costs