Little Sleepies Baby Size Chart — Fit by Weight & Height
The Little Sleepies baby-clothing size chart, size by size — the weight and height each label covers, and how Little Sleepies compares with the Size Index median for each size (taken across the distinct brand charts that print a weight for it). Based on the brand’s own published chart (retrieved 2026-09-02); we compare published charts and do not handle or test any garment.
Little Sleepies’ chart is sleepwear-led, so our Size Index does not rank it as running big or small. The table below shows each Little Sleepies size next to the Size Index median, without an overall verdict.
Little Sleepies baby size chart (weight & height)
| Size | Fits weight | Height | Size Index median | Little Sleepies vs median |
|---|---|---|---|---|
| Micro Preemie | up to 3 lb | up to 15 in | — | — |
| Preemie | 3–5 lb | 15–18 in | 5.5 lb | −0.5 lb |
| Newborn | 5–8 lb | 18–21 in | 8 lb | 0 |
| 0-3m | 8–12 lb | 21–23 in | 12 lb | 0 |
| 3-6m | 12–17 lb | 23–27 in | 17 lb | 0 |
| 6-9m | 17–20 lb | 27–29 in | 20 lb | 0 |
| 6-12m | 17–23 lb | 27–31 in | 22 lb | +1 lb |
| 12-18m | 23–26 lb | 31–33 in | 27 lb | −1 lb |
| 18-24m | 26–30 lb | 33–34.5 in | 30 lb | 0 |
| 2T | 29–31 lb | 33–36 in | 30.5 lb | +0.5 lb |
| 3T | 31–35 lb | 36–39 in | 34 lb | +1 lb |
Read the “vs median” column to see where Little Sleepies differs: a positive number means that size covers heavier babies than the typical brand (runs bigger on paper); negative means smaller. Compared across 10 matching sizes.
How we built this
There is no US standard for baby-clothing sizes, so the same label fits different weights at different brands. This page reproduces the Little Sleepies published size chart and compares each size to the Size Index median for that size, taken across 12 to 27 distinct brand charts depending on the size, from our 30-brand Baby Clothing Size Index 2026. Figures are from the brand’s published chart (retrieved 2026-09-02); we compare published charts only and never claim to have measured or tested a garment. For clothing fit only — not a guide to how much a baby should weigh.