How to buy clothes online that actually fit

Measure yourself once, and keep the numbers

Use a soft tape measure and keep it snug but not tight. Write the numbers down in centimetres, because most size charts use them. One inch is 2.54 centimetres if a chart only shows inches.

• Chest or bust: around the fullest part, with the tape level across your back.
• Waist: around your natural waist, usually just above the belly button.
• Hips: around the widest part of your hips and seat.
• Inseam: from the crotch down to where you want the trousers to end.
• Feet: stand on paper, mark your heel and longest toe, and measure the distance. Do it in the afternoon, when feet are slightly bigger.

Compare with clothes you already own

Your body measurements tell you what fits you, but many size charts describe the garment itself. The easiest fix is to lay a top or pair of trousers that fits you well flat on a table and measure it: armpit to armpit, the length from shoulder to hem, and the waist straight across. Double the straight-across numbers and compare them with the shop's chart.

Read the size chart, not the size label

Sizes are not standard between shops. Many sellers' sizes run smaller than you may be used to, and a few run larger, so don't order your usual letter without checking. Look for the shop's own chart in the listing photos or description, and check whether its numbers are body measurements or garment measurements.

• If you are between two sizes, choose the bigger one for fitted items and non-stretch fabrics.
• Check whether the listing says the item is meant to be oversized or slim fit.
• For shoes, compare your foot length in centimetres with the chart, and allow a little room in front of your toes.

Check the fabric, because it changes the fit

Fabrics with some elastane or spandex stretch and forgive small sizing mistakes. Plain cotton and linen don't stretch much, and 100% cotton can shrink a little in the first wash, especially in hot water or a dryer. If the listing doesn't list the fabric, ask the seller before you buy.

Let other buyers help you

Reviews with photos are the most useful, especially when buyers mention their height, weight or usual size and whether the item ran small or large. If several reviews say the same thing, believe them over the chart.

Know the return rules before you order

Check whether the shop accepts returns or exchanges for the wrong size, how many days you have, and who pays for the return shipping. Keep the tags on and the packaging until you're sure the item fits.