COS Sizing: Does COS Run Small, Big or True to Size?

COS can run big in its deliberately oversized cuts, so the answer to "does COS run big" is yes for some pieces, not as a brand-wide rule. The US chart maps XS to US 2 and EU 32, S to US 4 or 6 and EU 34 or 36, M to US 8 or 10 and EU 38 or 40, L to US 12 or 14 and EU 42 or 44, and XL to US 16 and EU 46. That means a letter label can cover more than one numeric size, and an EU label may be more useful if you are comparing tags internationally. COS lists chest, waist, arm and low-hip measurements, but its own guide says to use garment-specific lengths too because some pieces are designed uniquely. Product descriptions also state model size and garment length, and a size 6 back length is more helpful than broad advice if you are choosing a long shirt. I treat the word oversized as a pattern note, not a command to size up. For a regular piece, begin with the chart and compare measurements; for an oversized cut, decide how much ease you actually want.

The clearest examples are the shirts. The Oversized Short-Sleeved Linen Shirt and Oversized Short-Sleeved Cotton Shirt both use boxy, oversized cuts, with COS listing size 6 as the model size and the same 23.7-inch back length. The Oversized Folded-Collar Cotton Shirt is also marked oversized, but its longer body has a 29.69-inch back length; the Oversized Satin T-Shirt has side slits and a loose drape. I would not size down on the basis of the category name alone: a short boxy shirt and a long shirt can feel very different on the same body. If you want the intended roomy line, start with your chart size; if you want a closer shoulder and less volume, use the product's model size, length and fit note to consider one size smaller. For an online order, keep the tags on until you have checked the shoulder, sleeve and hem with the shoes you will actually wear.

COS jeans are not all oversized. The Inlet Boucle Curved-Leg Jeans are relaxed fit, mid-rise and full length, with a 29.92-inch inside leg in size 28. The Valley Cropped Bootcut Jeans are slim through the hip and thigh, high-rise and ankle length, with a 27.83-inch inside leg in size 27. For trousers, Pleated Balloon Pants are relaxed and have adjustable tabs inside the waistband, while Corduroy Barrel-Leg Drawstring Pants are marked regular fit. My tip is to compare the rise and inside leg with a pair you already wear, not just the letter or numeric size on the label. A curved jean can feel roomy through the leg while still sitting close at the waist; a slim bootcut has a different job. Use the size chart for your starting point, then trust the fit line and garment measurements for the style in front of you.

Outerwear is where the contrast is clearest: the Oversized Cropped Boiled Wool-Blend Blazer is cut oversized, while the Tailored Wool-Blend Double-Breasted Coat is marked regular fit. The Oversized Double-Faced Wool Shawl Coat is another roomy silhouette, but the Sculpted Wool-Blend Zip-Up Jacket is marked regular fit despite its enveloping shape. That is why I would follow the fit line and model size, not assume one COS rule. The product pages give back lengths for each piece, which makes it easier to judge sleeve and body proportion before buying. COS accepts full-price returns within 30 days and eligible sale returns within 14 days; mail returns have a fee, and in-store returns are free. If you are between sizes, decide whether you plan to layer a thick knit under the coat and compare its garment measurements. My simple call is to begin true to the chart in regular cuts, then size down only when an oversized shape looks larger than you want.