The honest answer is that nobody publishes a number for it, and that includes us. None of the makers behind the current winter kit publishes a grow-into-it allowance, and no source we hold gives a rate at which a particular child grows. What you can decide on is what is actually knowable: what the maker publishes, what the garment does on the child today, and how much time you leave yourself.
There is no size-up rule
Buying a size up as a general policy is not a rule any of these makers publish. How much room to leave depends on the garment, not on a rule of thumb. Where a maker publishes an extendable feature we will say so, and where it does not, we will not invent one.
A size step chosen in advance also has a cost on the day it arrives, and the boot is where it shows. A boot that is too large lifts at the heel, lets the foot slide inside, and changes how the child walks. Those three observations are what we use in place of a size rule.
What the makers of this kit actually publish
None of the current pieces publishes a growth allowance. Several publish adjustment, which is a different thing and still worth knowing.
| Piece | What the maker describes |
|---|---|
| Perlimpinpin two-piece snowsuit | Adjustable wrists and adjustable straps |
| Deux par Deux baby one-piece snowsuit | Fold-over hand and foot panels |
| Deux par Deux Brown Sugar winter boots | Barrel-adjusted laces and a removable liner |
Those are the makers' own descriptions of fit and closure. None of them is published as a way to buy early and grow into it, and we are not going to present them that way. Deux par Deux publishes no between-sizes rule for the boot at all.
What decides it instead
Three things you can observe or state today.
- The measurement, read against that product's own chart. Not the size the child wears in another brand.
- The layers going underneath, and how much the child moves. Both change what fits. Tell us both and we will say when the next size is worth considering, and why.
- Where the measurements disagree. A child whose chest selects one size and whose height selects another is the case a chart cannot resolve, and naming it beats picking one quietly.
Re-measure instead of predicting
The measurement that answers the March question is the one taken in March. Repeat the standing foot measurement as the foot grows, or when the planned sock or liner changes, and check the fit on the child rather than against the calendar.
Leave time before the day the gear is needed, so there is room for a fit check and, if the size misses, an exchange. When shopping opens, a kit we recommend will include a free size exchange when the fit misses, with shipping on us.
To take the measurements first, start with how to measure your child for winter gear. For a size on each piece against its own maker chart, send the measurements through the Fit Finder.