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size guide

find their
perfect fit.

Our zippies run true to size. Sizing by weight + height beats sizing by age every time — babies don't read calendars. When in doubt, size up: bamboo stretches, and chubby thighs are an asset, not a problem to solve.

the chart ✦

Preemie
age
< 0
weight
up to 5 lb
height
up to 17"
Newborn
age
0–1 mo
weight
5–8 lb
height
17–21.5"
0–3 mo
age
1–3 mo
weight
8–12 lb
height
21.5–24"
3–6 mo
age
3–6 mo
weight
12–17 lb
height
24–26.5"
6–9 mo
age
6–9 mo
weight
17–20 lb
height
26.5–28.5"
9–12 mo
age
9–12 mo
weight
20–24 lb
height
28.5–30.5"
12–18 mo
age
12–18 mo
weight
24–28 lb
height
30.5–32.5"
18–24 mo
age
18–24 mo
weight
28–32 lb
height
32.5–34.5"
2T
age
2 yr
weight
28–32 lb
height
33–36"
3T
age
3 yr
weight
32–37 lb
height
36–39"
4T
age
4 yr
weight
37–42 lb
height
39–42"

✦ All measurements are body measurements, not garment measurements. Garments are designed for snug fit per U.S. flammability law for non-flame-resistant sleepwear.

when to size up

  • Between sizes by weight? Pick the larger one — bamboo stretches a little, but it shouldn't be tight at the thighs or shoulders.
  • Long torso / tall for age? Length matters most for footed sleepwear. Size up if their last footed pair was pulling at the toes.
  • Heading into a growth spurt? 4–6 weeks is the typical interval. Size up if they're at the top of the current range.

how to measure

  • Weight: easiest at the pediatrician or on a kitchen scale (you holding them, then minus your weight).
  • Height: lay them flat on their back on a soft surface. Mark the top of the head and the heel; measure the gap.
  • Cheat code: our sizing matches most major U.S. baby brands (Carter's, Kyte, Kickee). If their current zippered footie fits, the same size in ours will too.

why snug isn't optional.

U.S. federal law (16 CFR Part 1615/1616) requires kids' sleepwear to either be flame-resistant or snug-fitting. We chose snug. No chemical flame retardants, no extra fabric to bunch up around a sleeping baby — just a clean, close fit that follows the body.

That means our zippies will look fitted, not flowy. If a piece feels loose enough to slip a finger between fabric and skin almost everywhere — it's likely the wrong size. Trust the chart, trust the snug.

quick tips

gifting? newborn? in a hurry?

gifting

When the baby's not born yet, skip Newborn entirely — they grow out of it in 2–3 weeks. Go 0–3 mo or 3–6 mo for a longer wear window.

newborns

Tiny-but-mighty? Preemie fits up to 5 lb. Most full-term newborns will start in Newborn (5–8 lb) and move to 0–3 mo within the month.

end of a size

If they're at the top of the current weight range AND the footed parts are pulling, it's time. Don't squeeze another wear out — size up.

still not sure?
we make returns easy.

Order a size, try it on, send it back if the fit's off. Sizing baby clothes is hard — that's on us, not on you.

read returns policy shop all zippies