What the number changes, one band at a time
350gsm is where a hoodie stops draping and starts holding. A 350 fleece hood is stiff enough to stand, which is the effect most buyers are actually after when they ask for heavy.
400gsm is the practical ceiling for a garment that still ships economically. The garment is dense, the print sits high on the surface, and the parcel weights are visibly different from a 320.
450gsm and above is a deliberate cost decision. The fabric costs more, the sewing is slower, and volumetric weight usually overtakes everything else. It exists for brands whose product is the weight itself.
- 350gsm: hood stands, shape holds, still ships sensibly.
- 400gsm: dense hand, prints sit high, visible freight step.
- 450gsm+: statement garment, freight dominates the landed cost.
The parts that must change with the weight
Rib. At 350gsm and above, 2x2 rib with elastane is not optional. A light rib on a heavy body stretches out at the cuff within a few washes and the whole garment reads cheap, regardless of how good the body is.
Hood construction. A two-panel lined hood on 400gsm adds structure that a single-layer hood cannot fake. On a heavy body a single-layer hood looks like an afterthought.
Seams. Overlocked seams on 450gsm produce a ridge you can feel through the fabric. Flatlock or taped seams are the difference between "premium" and "heavy but rough" in the hand.
Shrinkage is not a rounding error at this weight
More yarn means more relaxation on the first wash. A 400gsm loopback can lose 6–8% in length where a 180gsm jersey loses 3–4%. That is a full size at the top of the run.
The control is procedural, not technical: wash the sample, measure it, and approve the size chart from the washed sample. Approving from the unwashed sample is the single most common cause of returns on heavy hoodies.
When not to go heavy
If the garment is a giveaway, a staff uniform, or anything shipping in volume at a low price, the weight is working against you: it costs more, ships worse and shrinks more.
If the climate is warm for most of the selling season, 320–350gsm sells better than 400 regardless of what the reference brand is doing.