Babywear looks like the easy end of apparel grading. The garments are small and the measurements are short, which makes errors feel insignificant. They are not — the increments are small too, so a two-centimetre error is proportionally much larger than it would be on an adult garment.
The usual size ladder
Most ranges run 0-3M, 3-6M, 6-12M, 12-18M, 18-24M. Some add a newborn size and some extend to 2-3Y. The published size charts on the factory's own product sheets show the increments used for the styles in this range — for example a bamboo romper grading body length 52 / 57 / 63 / 70 / 77 cm and half-chest 19 / 20.5 / 22 / 23.5 / 25 cm across the five sizes, with sleeve length 22 / 24 / 26 / 28 / 30 cm.
Two things are visible in that sequence. First, the increments are not equal — they grow with the size. Second, the chest increment is smaller than the length increment, which is correct: babies gain length faster than they gain girth.
Why linear grading fails
The most common grading error is applying a constant increment across the whole ladder. If chest grows 1.5 cm per size at the bottom of the range, it cannot keep growing 1.5 cm at the top, because the child's growth curve does not work that way. A linearly graded range either strangles the largest size or swamps the smallest.
The second common error is grading one dimension in isolation. Lengthen the body without widening the neck opening and the largest size becomes impossible to get over a head.
The ends of the range are where it shows
Grading errors hide in the middle. A size set is inspected at both ends:
- 0-3M: does the neck opening clear a newborn head without over-stretching? Does the leg opening clear a nappy? Is the body length right for a baby who is mostly lying down?
- 18-24M: does the bodysuit still have room for a nappy? Does the shoulder stay on the shoulder once the child is upright and moving? Do the snaps still hold under a walking child's movement?
What to check on a size set
- Measure every size against your table, not just the middle one.
- Put the smallest and largest on a body — a mannequin or a child — not just on a table.
- Wash the smallest and largest, then re-measure. Shrinkage does not apply evenly across a range.
- Check the grade holds in the fabric you are actually shipping, at the weight you are shipping. A grade that works in a 180 gsm interlock may not work in a 280 gsm terry.
- Confirm the snaps and closures are in proportion — a snap spacing that suits a 0-3M garment is usually wrong at 18-24M.
Age labels versus actual fit
Age labelling is a convention, not a measurement. Babies of the same age vary enormously in size, and different markets have different expectations about whether the label reflects age or size. Decide early whether your labels mean "typically fits a child of this age" or "fits a child in this measurement range", and make sure the size chart on your listing says the same thing as the label in the garment.
If you do not have a measurement table, ask the factory for one for the style you are quoting, then approve it in writing before sampling. It is much cheaper to argue about a table than about a size set.