The label is Italian sizing, not a waist figure
Gucci builds its trouser range on Italian sizes, and the men's bottom-wear chart runs from IT 40 at the bottom to IT 60 at the top, with a letter attached to the middle block: IT 42 is XXS, IT 44 is XS, IT 46 is S, IT 48 is M, IT 50 is L, IT 52 is XL, IT 54 is XXL and IT 56 is XXXL. The sizes above and below that block are published as numbers only. Gucci's women's bottom-wear chart uses the same Italian scale but starts lower, at IT 34, and it adds the EU, UK/AU and JP columns that the men's trouser chart does not carry. In the women's chart the EU size runs four numbers below the Italian one — IT 38 is EU 34 — which is the usual Italian-to-European offset, so a pair marked IT 48 is an EU 44 in the same house's own columns. Treat the Italian number as the anchor and convert outwards from it.
Reading the waist and hip columns correctly
The measurement columns are the ones to compare, and they do not agree with the jeans column beside them. Gucci lists IT 46 as a 75 cm waist and 29.5 in with 95 cm hips, but pairs it with a jeans size of 32 to 33. The centimetre figure is the one to trust, because a nominal jeans size describes the body a wearer buys jeans for rather than the trouser's own waistband. The pattern holds up the range: IT 48 is 79 cm and 31.1 in with 99 cm hips against jeans 34 to 35, IT 50 is 83 cm and 32.7 in with 103 cm hips, and IT 52 is 87 cm and 34.2 in with 107 cm hips. If you know the waistband of a trouser you already own, compare it with those centimetre figures and treat the jeans number as a rough cross-check instead of the measurement.
Straight, tailored and drawstring cuts
Gucci's trouser range covers three quite different leg behaviours. The straight-legged styles keep a consistent width from the thigh to the hem, and the GG cotton gabardine pant is described in exactly those terms — straight-legged, and finished with an elastic waistband and drawstring rather than a fixed waist. The tailored group is cut to a regular fit with a straight leg and traditional finishing: belt loops, a hook and zip closure and a defined waistband that sits where the chart says it should. Then there are the softer drawstring and jogger styles, where the waist is elastic and the leg is cut to fall the same way front and back. Between sizes, the cut matters more than the centimetres, because a straight tailored waistband has almost no give while an elastic drawstring one will adjust through a meal and a day of sitting.
Fabric tells you how the leg hangs
The fabric line on each Gucci trouser is short, and it explains the drape. The GG cotton gabardine pant is 100% cotton, a tightly woven twill with a dry hand that holds a crease and keeps a straight leg looking architectural. The GG jacquard trouser with Web is a polyester jacquard with a much softer fall, so the same straight cut reads slimmer and moves with the leg. Cotton and cotton-blend pieces also crease visibly after a long day, which turns into a fit question in practice: a straighter cut in a stiff gabardine keeps its line, while the same cut in a flowing jacquard will follow the body underneath. If the two pairs are the same size on paper, the fabric is what you will actually notice after an hour of walking.