Photo par Liza Summer via PexelsOrdering clothes online removes the option of trying them on before paying, which makes choosing the right size trickier than shopping in store. Knowing how to choose your clothing size online relies on a simple method: take your own measurements, compare them against each brand’s own size guide, and watch for the mistakes that come up most often with remote orders. This guide walks through each step to cut down on returns caused by the wrong size.
Take your measurements before placing an order
The first step does not depend on any brand: it means measuring your own body with a soft tape measure, without pulling it tight, to get reliable figures you can reuse on any site.
Bust and waist measurements
The bust is measured at its fullest point, with the tape passing horizontally across the back. The waist is measured at the narrowest point of the torso, generally just above the navel, without holding your stomach in. These two measurements drive most upper-body garments: shirts, jumpers, dresses and jackets.
Hip measurement and leg length
The hip measurement is taken at the widest point, with the tape held flat against the body. For trousers or a skirt, inseam length (from the crotch to the desired hem) usefully completes these measurements, especially for jeans or tailored trousers.
Read and interpret the brand’s size guide
Once you have your measurements in hand, the next step is to check them against the size guide published on the site, rather than relying on your usual size. Two brands can use the same size label (M, 10, or 12) for different measurements.
Size guides for women’s clothing
For women’s clothing, fit differences are common between a fitted piece and an oversized one: the same size number does not produce the same result. Our women’s body shapes guide explains how the same size can fit differently depending on body shape, and why the size guide should always take priority over habit.
Size guides for men’s clothing
For men, charts generally distinguish a regular cut from a slim cut, with differences of several centimetres at the same labelled size. For trousers, choosing the right cut matters as much as the size itself, as detailed in our which jeans for your body shape guide, which applies to most men’s and women’s trousers.
International size conversion chart
Sites that sell foreign brands sometimes display sizes in UK or US formats rather than local sizing. This chart gives a general correspondence, to be checked systematically against each brand’s own guide before placing an order.
| Letter size | France | UK | US |
|---|---|---|---|
| XS | 34 | 6 | 2 |
| S | 36 | 8 | 4 |
| M | 38-40 | 10-12 | 6-8 |
| L | 42-44 | 14-16 | 10-12 |
| XL | 46-48 | 18-20 | 14-16 |
These correspondences remain indicative: cut, fabric and style make the final fit vary from one brand to another, even at the same labelled size.
Mistakes that throw off size choices online
Several habits come up again and again and throw off size choices when shopping remotely. Relying only on your usual size without checking the site’s own guide is the first one: two brands do not necessarily use the same reference chart for the same number.
Ignoring fabric composition is a second one: a stretch fabric (elastane, jersey) tolerates a wider margin of measurement than a rigid fabric such as raw denim or non-stretch cotton canvas. Skipping customer reviews is another common bias: they often mention whether a specific item runs large, runs small, or matches the published guide faithfully.
Finally, not checking the return policy before ordering makes it harder to correct a sizing mistake. Our comparison of the best online clothing sites covers the return policies of the main platforms in detail, a criterion worth checking before placing an order rather than after receiving a parcel.
What to do when in doubt between two sizes
When your measurements fall between two sizes on the chart, the most reliable rule is to adjust based on the type of garment. On a fitted top, choosing the larger size avoids discomfort from fabric pulling too tight across the chest or shoulders. On a garment that is already loose by design (an oversized sweatshirt, a wide-cut shirt), the smaller size is usually enough, since the cut itself absorbs the measurement gap.
For trousers, it is better to prioritise the hip measurement over the waist measurement when in doubt: a waist that is too loose is easily tightened with a belt, while hips that are too tight cannot be corrected.
Frequently asked questions
How can I know my clothing size before ordering online?
Take your own measurements with a soft tape measure, without pulling it tight, then compare those figures to the size guide published by the brand rather than to your usual in-store size. Each retailer builds its own reference chart, which explains the gaps between brands for the same size label.
Does a size 12 correspond to a medium or a large?
This depends entirely on the brand and the cut of the garment. Some retailers with a looser fit classify a size 12 as a medium, while others, on a more fitted cut, place it in large. The brand’s own size chart, or failing that its detailed measurements per size, remains the only reliable source to decide.
Should you always size up when ordering clothes online?
No, this reflex is not a general rule and can result in an oversized garment. It is more reliable to check the fabric (a stretch fabric tolerates a wider margin than a rigid fabric) and to read customer reviews, which often mention whether a specific item runs large or small.
What should you do if your bust and waist measurements fall into two different sizes?
In that case, on a top, choosing the size that matches the wider measurement, and adjusting afterwards with a belt or a tailoring fix if needed, avoids the discomfort of a garment that is too tight. On bottoms, the opposite generally applies, since a waist that is too loose is easier to fix than hips that are too tight.