French terry is the workhorse fabric of contemporary casualwear. It is smooth on the outside, looped on the inside, and sits in a comfortable middle ground between a jersey tee and a full fleece. Sourcing it well requires understanding three things: GSM, loop construction, and washing behaviour.
GSM: the number that matters most
GSM (grams per square metre) is the primary spec for any knit fabric. French terry for lightweight summer sweatshirts typically runs 220–260 GSM. For mid-weight, 260–300 GSM. Anything above 300 starts to feel like a proper sweatshirt fleece. Always confirm GSM on a finished, washed sample — mills often quote pre-wash GSM, which runs 5–10% lighter than the finished garment.
The fibre content affects how GSM translates to hand feel. A 280 GSM 100% cotton terry feels quite different from a 280 GSM 85/15 cotton-polyester blend. The blend shrinks less, holds its shape better through washes, and typically pills less at stress points like the armhole and pocket opening.
Loop construction
The loops on the interior of french terry are what trap air and give the fabric its warmth-to-weight ratio. Tight, even loops indicate a well-tensioned knit and consistent GSM across the fabric width. Loose or uneven loops suggest the knit was rushed or the yarn tension was inconsistent — both problems that will show up as distortion after washing.
Ask your mill for a 50 cm × 50 cm sample and wash it three times at 40°C before you approve it for bulk production. Measure the shrinkage in both directions (warp and weft). Anything above 5% in either direction needs to be factored into your pattern, or you need to find a different fabric.
What to ask the mill
When you spec french terry, always confirm: pre-wash and post-wash GSM, shrinkage percentage in both directions, loop height and loop tightness, pilling resistance rating, and available widths. A 160 cm width is standard; narrower widths mean more fabric waste in cutting.
The mills that cannot answer these questions clearly are the mills that will cause you problems at the seam allowance stage. Good terry is easy to spec. The hard part is finding a mill that takes your quantities seriously.