Onesie and bodysuit are two names for the same garment — a one-piece top that snaps at the crotch — while a romper adds legs (no feet) and a footie is a full-length one-piece with feet. The catch: our study of 30 brands sold in the US found the same "3–6M" label tops out anywhere from 14.5 lb to 20 lb depending on the brand, so buy by weight, not the label.
- Onesie and bodysuit are the same thing — a crotch-snapping top worn as a base layer. "Onesies" is a trademark; bodysuit is the generic word.
- Legs but no feet = romper (a standalone outfit). Legs plus feet = footie (a full-length sleeper).
- A sleep sack is a wearable, sleeveless bag worn over clothes — a garment, not bedding.
- Snug-fit sleepwear is made to fit close by design (see the CPSC note below).
- The label alone is unreliable. Our size study of 30 brands sold in the US found the same "3–6M" label tops out anywhere from 14.5 lb to 20 lb depending on the brand.
What are the main types of baby clothes?
There are seven pieces that make up almost every baby wardrobe. The table below defines each one, tells you whether it has feet, where it fastens, and when to reach for it. Use it as a quick reference, then read our baby clothing size index of 30 brands sold in the US before you commit to a size.
| Type | What it is | Has feet? | Snaps where | Best use |
|---|---|---|---|---|
| Bodysuit (onesie) | One-piece top that fastens under the crotch | No | Crotch, plus an envelope neck at the shoulders | Base layer under everything, all year |
| Romper | One-piece outfit with short or long legs | No | Crotch, sometimes down the front | Standalone warm-weather outfit |
| Footie (footed sleeper) | Full-length one-piece with attached feet | Yes | Full zip, or snaps down the front and legs | Sleep and cool-weather all-day wear |
| Coverall / sleeper | Full-length one-piece with legs, no feet | No | Zip or front snaps | Layering, and older babies who stand and walk |
| Kimono / side-snap bodysuit | Bodysuit that wraps and fastens at the side | No | Side, plus the crotch | Newborns; no pulling over the head |
| Two-piece set | A separate top and bottom | No | Usually pull-on, no snaps | Older babies, easy outfit changes, style |
| Sleep sack (wearable blanket) | Sleeveless bag worn over other clothes | No | Zip or snap at the shoulders | A sleepwear layer worn over regular clothes |
What is the difference between a onesie and a bodysuit?
There is no difference — they are the same garment. "Onesies" is a registered trademark of Gerber, so most brands call the same piece a bodysuit. Either way it is a one-piece top that fastens with snaps under the crotch and usually has an envelope (overlapping) neckline so it can slide down over the shoulders as well as over the head. It is the workhorse base layer that goes under rompers, pants, and sleepers.
What is a romper and when do you use one?
A romper is a one-piece outfit with legs and no feet, designed to be worn on its own rather than as a base layer. Because it is a single piece, there is no top riding up and no waistband, which makes it comfortable for crawling and easy to throw on. Rompers usually have short legs for summer or long legs for cooler days, and they are a warm-weather favorite. A "jumpsuit" or "playsuit" is the same idea in slightly dressier or longer-legged form.
What is a footie or footed sleeper?
A footie (also called a footed sleeper, footed pajama, or sleep-and-play) is a full-length one-piece with feet built in, so you never lose a sock. It closes with a long zipper or a row of snaps and is the go-to piece for sleep and for cool-weather days. If a footie is sold as sleepwear, the US Consumer Product Safety Commission (CPSC) requires it (above size 9 months) to be flame-resistant or snug-fitting, so follow the garment label and CPSC's children's sleepwear guidance rather than sizing it up - a CPSC rule, not a Babbez recommendation. Always follow the garment's own care and safety label.
The fit and flammability points above are general product information, not safety advice. For anything about your baby's sleep, follow the manufacturer's label and see our medical disclaimer.
What is a coverall or a sleeper without feet?
A coverall is a full-length one-piece with legs but no feet — think of a footie that stops at the ankle. Brands also call this a footless sleeper or simply a coverall. It layers cleanly over a bodysuit, works well once a baby is standing and cruising (feet get traction on the floor), and pairs with socks or booties when it is cool. It is the natural next step up from footies for many families around the crawling-to-walking stage.
What is a kimono or side-snap bodysuit?
A kimono bodysuit wraps across the chest and fastens with snaps at the side instead of pulling over the head. Because nothing goes over the face, many parents find it the easiest style for newborns and for the early weeks. It does the same job as a standard bodysuit — a crotch-snapping base layer — just with a gentler on-and-off. Side-snap tops and gowns follow the same wrap-and-snap idea.
Do you need two-piece sets?
Two-piece sets (a separate top and bottom) become genuinely useful once a baby is older and outfit changes get frequent. They let you swap just the messy half, mix and match, and dress a mobile toddler who has opinions. For newborns, one-piece bodysuits and footies usually win because there is no gap at the waist and less to fasten. A good wardrobe holds mostly one-pieces early on, then shifts toward sets as your child grows.
Is a sleep sack clothing?
Yes — a sleep sack, or wearable blanket, is a garment: a sleeveless, footless bag that zips or snaps at the shoulders and is worn over regular clothes. The American Academy of Pediatrics (AAP) points to wearable blankets like sleep sacks as an alternative to loose bedding and publishes official safe-sleep guidance that covers how and where a baby should sleep. Babbez sizes sleep sacks as clothing (by weight and height) but does not give medical or safety advice — for the sleep rules themselves, follow the AAP guidance below.
This is general clothing information, not medical or safe-sleep advice. Please follow the AAP or your pediatrician and read our medical disclaimer.
What size and how many of each do you need?
Buy by measurement, not by the number on the tag. Our size study of 30 brands sold in the US found the same label can mean very different garments: a "3–6M" label tops out anywhere from 14.5 lb to 20 lb depending on the brand, and an "18–24M" label anywhere from 26 lb to 32 lb. The table below is a rough starting point — treat every range as approximate and always check the brand's own chart, or use our free baby clothes Size Finder.
| US size label | Roughly the age | Approx. weight (varies by brand) |
|---|---|---|
| Newborn (NB) | 0–1 mo | up to ~9 lb |
| 0–3M | 0–3 mo | ~9–12 lb |
| 3–6M | 3–6 mo | upper limit varies 14.5–20 lb across brands (our data, 30 brands) |
| 6–12M | 6–12 mo | ~17–22 lb |
| 12–18M | 12–18 mo | ~22–27 lb |
| 18–24M (about 2T) | 18–24 mo | upper limit varies 26–32 lb across brands (our data, 30 brands) |
The two "our data" rows are the full spans we recorded across brands, which is why they look wider than a single baby — that spread is exactly why the label alone is unreliable. European brands work differently again: the size is simply the child's height in centimeters (size 62 means about 62 cm tall), which you can map with our guide to converting European sizes 50 to 140. As for how many, most families do well with roughly 6–8 bodysuits, 4–6 footies or sleepers, and a couple of rompers or sets per size; our baby clothes registry checklist breaks the full first-year list down piece by piece.
Sources: American Academy of Pediatrics (AAP), A Parent's Guide to Safe Sleep; U.S. Consumer Product Safety Commission (CPSC), Children's Sleepwear Regulations, 16 CFR 1615 and 1616; Babbez Baby Clothing Size Index 2026 (30 brands sold in the US). This article is general clothing information and is not medical or safety advice — see our medical disclaimer.
