Jeans stretch out because most of them are engineered to. Anything with elastane will give roughly half a size through the day and mostly spring back overnight, while a rigid all cotton pair will stretch at the waist and knee and stay there until you wash it. That is the whole trade, and it decides whether you buy your true size or size down a hair. I have ruined enough pairs by guessing to have a rule now: rigid cotton, buy snug; stretch denim, buy true. Below, the straight and barrel legs I trust to hold, the wide and relaxed cuts where a little give is the point, and the slim pairs that live or die on their recovery. The other half of the answer is where a pair stretches, because it is never uniform. The waistband goes first, then the seat and the knee, and the hem stays exactly where it was, which is why a pair that has relaxed reads as slightly baggy in the middle rather than longer.

Straight and barrel legs are where fabric weight shows up fastest. A heavy cotton holds the leg line all day; a thin stretch version collapses into a soft tube by lunch. These are the ones with enough body to keep the shape they were cut with. Weight is the number worth knowing here. Anything from about twelve ounces up will hold a leg line through a full day; below ten ounces you are buying comfort rather than structure, and the leg will soften into whatever shape you sit in. A rigid pair in this category will feel stiff for the first week and then mould to you permanently, which is the entire argument for buying them snug.

Wide and relaxed jeans are the forgiving category, because a half size of give disappears into the volume. This is where I stop worrying about recovery and start thinking about hem length, which matters far more here. Length is what actually matters in this category, because a wide leg has nowhere to put excess fabric. Buy for the shoe and hem from there. The second thing to check is the rise: a high waist keeps volume anchored where a low rise lets the whole thing slide down as the day goes on, which is the real reason relaxed jeans sometimes feel like they are falling off.

Slim and skinny jeans are the real test. Recovery is the word to look for, and in practice it means the pair still fits at 7pm the way it did at 9am. The ones below have enough elastane to move and enough structure to bounce back. Look for elastane somewhere between one and three percent. Below that a slim pair will feel like a rigid trouser; above it the fabric starts to behave like a legging and the recovery gets worse rather than better, because there is more to relax and less cotton holding the structure. Anything described as having a comfort or knit waistband belongs here too, and those keep their fit best of all.

Liverpool Los Angeles builds most of its denim around a comfort waistband, which is the honest answer to the stretching-out problem: instead of pretending the waist will not move, it is engineered to move and return. Their Kennedy straight and Stride wide leg are the two I would start with. The range is broad enough to compare cuts against each other in one place, which is genuinely useful when you are trying to work out whether you want structure or give. Prices sit low enough that owning two rises rather than agonising over one is a realistic plan.

A few more, across rises and hems, for when you know your cut and just want the right wash. Cropped hems, flares, boot cuts and the high and mid rises, gathered together so you can compare washes rather than construction. Everything here follows the same rules as the grids above, so once you know whether you want rigid or stretch, this is where to find the version in the colour you actually wanted.

One last thing, because it is the fix nobody wants to hear: if a stretch pair has gone soft and baggy, a warm wash and a low tumble will bring most of it back. Heat is what resets the elastane. It is not a myth and it costs nothing to try before you give up on a pair you like. Rigid cotton is different, and honestly that is the appeal. It stretches to you and stays there, which is why a broken-in pair of all cotton jeans fits better in year three than it did in week one.