The short answer
Plan on about 6 bodysuits and 5 sleepers in each size if you do laundry every 2 days. Newborns go through more than you'd expect, because spit-up and diaper leaks mean changes, so the real number depends mostly on how often you wash.
| Laundry | Bodysuits | Sleepers |
|---|---|---|
| Every day | 4 | 3 |
| Every 2 days | 6 | 5 |
| Every 3 days | 8 | 6 |
| Once a week | 16 | 12 |
Assumes 2 bodysuits and 1.5 sleepers a day, plus a spare set while a load is washing and drying.
Newborn size or 3 months?
Baby clothes go by weight, not age. On Carter's size chart, Newborn fits 6 to 9 lb and 3M fits 9 to 12.5 lb. A baby born at the average weight (7 lb 4 oz) is in Newborn size for only about 3 weeks on our growth estimate, and a baby born at 9 lb or more skips it. So buy just one set of Newborn, and put most of your budget into 3M and 6M.
| Carter's size | Weight |
|---|---|
| Preemie | Up to 6 lb |
| Newborn | 6–9 lb |
| 3M | 9–12.5 lb |
| 6M | 12.5–17 lb |
| 9M | 17–21 lb |
From the Carter's size chart, checked October 12, 2026. Other brands run a little differently, and length matters too: size up when snaps strain or feet are cramped.
What changes with the season
- Hot months: short-sleeve bodysuits and light cotton sleepers. The AAP advises keeping babies under 6 months out of direct and indirect sunlight, with light, covering clothes and a brimmed hat when you go out. Source: AAP on baby sunburn prevention.
- Cold months: long-sleeve bodysuits, footed sleepers, and thin layers you can add. In the car, skip the puffy coat under the harness: the AAP says the padding flattens in a crash, leaving the straps loose. Dress in thin layers and put a coat or blanket over the buckled straps. Source: AAP winter car seat tips.
- For sleep, any season: the AAP says dress your baby in only one layer more than you are wearing, and use layers or a wearable blanket instead of loose blankets. Source: AAP safe sleep guide.
How we calculate
- Growth. The WHO Child Growth Standards, which the CDC recommends for babies under 2, from the CDC's data files. Your baby's birth weight sets their percentile, and we assume they stay on it.
- Sizes. Carter's weight ranges. We move up when your baby reaches the top of a size.
- Use per day. Our planning assumption: 2 bodysuits and 1.5 sleepers a day for the first 3 months, then 1.5 and 1. You can change all four.
- How many to own. A day's use times (days between washes + 1), for a spare set while one dries.
- Season. Each day's month, marked hot, mild or cold for where you live. That's our own simple map, so adjust for your local weather.
"Onesies" is a Gerber trademark. We say bodysuits, but we mean the same snap-crotch basics.
Next on your list
See when clothes, diapers and everything else fit into your weeks in the Due-Date Plan, work out diapers by size with the diaper calculator, or see the full minimal registry checklist.