The letters S, M, L, and XL do not represent the same measurements from one brand to another. An M at a fast fashion retailer may correspond to an S at a sports brand, and vice versa. This lack of a universal standard complicates shopping, especially online, where trying on items is impossible before receiving them.
Why sizes S M L XL vary between brands
No French or European regulation requires clothing manufacturers to use a single measurement chart for lettered sizes. Each brand defines its own ranges for bust, waist, and hip measurements for the same “M” or “L”.
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Competitive data clearly shows this. At O’Neill, a women’s S for tops corresponds to a bust measurement of 85 to 89 cm. At Kiabi, an S (size 36) starts at 82 cm for bust measurement. Terre de Marins associates S with the range 36/38, which is a bust measurement of 83 to 92 cm. The same S can cover a difference of nearly 10 cm depending on the brand.
Understanding the correspondence of women’s sizes s m l xl therefore requires reasoning in centimeters rather than letters. The letter is merely a relative marker specific to each manufacturer.
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Bust, waist, and hip: the three key measurements
Most size guides are based on three measurements taken directly from the body, without tightening the measuring tape.
- Bust measurement is taken at the fullest part of the bust, with arms down by the sides. This is the determining measurement for tops, blouses, and jackets.
- Waist measurement is taken at the natural waist, at the narrowest part of the abdomen. It is especially relevant for fitted dresses and high-waisted pants.
- Hip measurement (or hip circumference) is taken at the widest part of the hips. This is the key data for skirts, pants, and shorts.
If your measurements fall between two sizes, the most reliable practice is to choose the larger size. A slightly loose garment is more comfortable than one that is too tight, and everyday comfort outweighs a letter on the label.
Indicative correspondence of French sizes and letters
The table below summarizes the most common equivalences, compiled from the charts of several French retailers. These figures remain averages: always check the specific size guide for the brand in question.
| Lettered size | FR size | Bust measurement (cm) | Waist measurement (cm) | Hip measurement (cm) |
|---|---|---|---|---|
| S | 36/38 | 83-89 | 64-73 | 90-95 |
| M | 38/40 | 88-96 | 70-83 | 95-105 |
| L | 40/42 | 95-101 | 78-88 | 100-111 |
| XL | 42/44 | 100-106 | 83-94 | 105-117 |
The ranges intentionally overlap. A woman with a bust measurement of 95 cm can wear either an M or an L depending on the cut of the garment.
Height and inseam length: the data that classic guides ignore
Most size charts only consider bust, waist, and hip measurements. Height is, however, a determining factor, especially for pants and jumpsuits.
Some sports and activewear brands now offer Short, Regular, and Tall variants for the same S, M, L, or XL. Gymshark, for example, details several inseam lengths for the same women’s size. An L in “short” and an L in “tall” do not suit the same silhouette at all.
This approach remains minority. General retailers like Kiabi or La Redoute do not systematically offer these length variants. For online purchases, check if the size guide mentions an inseam length or a reference height. In the absence of this information, pants ordered in the correct lettered size may be several centimeters too short or too long.
American and European sizes: the conversion pitfalls
American sizes (US) add a layer of complexity. An American XS generally corresponds to a French 32, while an American M often equates to a 38. Field returns diverge on this point, as American brands themselves do not all follow the same chart.
At O’Neill, a women’s XS (tops) corresponds to an EU size 34, an S to 36, and an M to 38. At Kiabi, the XXS already corresponds to a French 32, which is a bust measurement of 78 cm. Direct letter-to-letter conversion between two brands from different countries is therefore risky.
For purchases on foreign sites, two precautions reduce the risk of error:
- Always prioritize the measurements in centimeters indicated in the site’s size guide, rather than the letter or number displayed.
- Check customer reviews that mention if the item “runs small” or “runs large.” Platforms like Amazon or Zalando now display an aggregated indicator based on buyer returns, visible directly on the product page.
- Note your own measurements once and for all and keep them accessible on your phone. Bodies change, but measuring your three circumferences once per season is enough to avoid most errors.
Extended sizing: beyond XL, a grid that expands
In recent years, several major retailers have expanded their collections beyond the classic XL. Sizes XXL, 3XL, and up to 4XL now appear in regular collections, and not just in separate lines labeled “plus size.” Terre de Marins, for example, offers correspondences up to 6XL (French size 52/54).
The expansion of size charts also modifies the correspondence of intermediate sizes. When a brand adds a XXS at the bottom of the chart or a 4XL at the top, the middle letters may shift one notch compared to the old chart. An M from a 2024 collection does not necessarily have the same measurements as the M from the same brand five years ago.
The only reliable constant remains the measuring tape. The letters on labels serve as a quick reference in-store, but they do not replace a verification of actual measurements, especially when the purchase is made without a fitting room.