Nothing ruins a cute matching-family moment like a onesie that won't snap or a tee that swims on you. Here's how to get the fit right the first time.
All Big Frenchies t-shirts and onesies are unisex and fit true to size. That said, every style has its own size chart, so it's worth a quick check before you check out, especially if you're between sizes.
Two measurements matter most:
Lay a similar garment you already own flat, measure it the same way, and compare it to our chart before you buy.
Babies grow fast in the first year. According to CDC growth chart guidance, that's completely normal, which is exactly why our sizing runs in tight two-to-three-month bands instead of broad ranges.
| Size | Chest Flat | Body Length |
|---|---|---|
| 0-3 months | 7¼" | 14¼" |
| 3-6 months | 8" | 15¼" |
| 6-12 months | 8¾" | 16¼" |
| 12-18 months | 9½" | 17¼" |
| 18-24 months | 10¼" | 17¾" |
If your little one is right on the edge between two sizes, it's usually smarter to size up rather than down.
| Size | Chest Flat | Body Length |
|---|---|---|
| XS | 16.5" | 24.75" |
| S | 17.5" | 25.38" |
| M | 18.5" | 26" |
| L | 19.5" | 26.63" |
| XL | 21" | 27.25" |
| XXL | 22.5" | 27.88" |
| Size | Chest Flat | Body Length |
|---|---|---|
| S | 18" | 27½" |
| M | 20" | 28½" |
| L | 22" | 29½" |
| XL | 24" | 30½" |
| XXL | 26" | 31½" |
You'll find this same chart, kept up to date, on our Size Guide page.
When in doubt between two sizes, remember that 100% organic cotton has a little natural give and softens with every wash, so a snug fit at first will relax over time. Ready to shop with confidence? Browse our organic cotton baby onesies or family organic cotton clothing.
$24.60
$29.25
$44.75
$36.75
$24.60
$24.60
