How many onesies (bodysuits) does a newborn need? By season and size

For a baby born on January 15, 2027 in Chicago, Cotokim's list counts 2 short-sleeve and 2 long-sleeve bodysuits in size NB, and 3 short-sleeve and 3 long-sleeve in size 3M. For a baby born on July 15, 2027 in Houston, size NB takes 4 short-sleeve and 1 long-sleeve. Both counts use balanced amounts, laundry every two days, a dryer and a home heated in winter.

Why the number changes

A single range for every newborn leaves out what moves the count. Cotokim's math looks at five things:

1. The weather of the months your baby wears each size. What matters is the weather of those weeks in your city, not the birth month alone. A month counts as cold when its average temperature is below 64 °F (18 °C) and as hot from 75 °F (24 °C) up; in between, it is mild. These cutoffs are a Cotokim proposal: we found no health source that sorts months by the outdoor temperature to dress a baby. In hot months the list moves to short sleeves and rompers; in cold months it adds cardigans and hats for going out.
2. How long each size lasts. Cotokim's list counts about 3 weeks in size NB and 8 weeks in size 3M, from the World Health Organization median growth curves ^{1 2} and the weight and length ranges on Carter's size chart ⁴. That is why the list keeps NB short and lets 3M cover the gap.
3. How often you do laundry, and the dryer. With laundry every two days and a dryer, the math counts 2 days of clothes in use; without a dryer, 3, because clothes need a day to dry. In the Energy Information Administration's 2020 survey, 102.32 million of the 123.53 million US homes had a clothes dryer ⁵. So Cotokim's list starts with a dryer: if you hang clothes to dry or share a laundry room in your building, answer no.
4. Whether your home is heated in winter. In the same survey, 117.74 million of the 123.53 million homes used space heating equipment ⁶. In a heated home, the clothes your baby wears indoors follow the room, not the street: cold months count as mild for bodysuits and sleepers, and only the clothes for going out follow the weather outside. This is a Cotokim rule, and Cotokim's list asks how your home is in winter.
5. How much slack you want. Essential is the minimum that works with your laundry routine, with no spare pieces. Balanced adds slack for spit-up days, clothes still in the wash and visits. Complete adds more and lets you do laundry less often.

The numbers by season

Bodysuits in sizes NB and 3M, balanced amounts, laundry every two days, with a dryer and a home heated in winter:

In hot weather, a short-sleeve bodysuit is often the whole outfit, which is why the hot column leans on short sleeves. Two answers change the table the most:

• A home kept cool in winter. All size NB clothes for cold months go from 14 pieces and 5 pairs to 20 pieces and 6 pairs, because clothes worn indoors then follow the cold.
• No dryer. All size NB clothes for mild months go from 12 pieces and 5 pairs to 16 pieces and 6 pairs.

How we count

The amounts on this page are a Cotokim proposal: we found no US government health source that gives a number of bodysuits. For each size, the list takes the outfit changes of a day, for spit-up, leaky diapers and baths, times the days of clothes in use until the next laundry, and adds the slack of the approach you pick. The tool on this page uses the same engine as the list by your city's weather, so the numbers match. How every number is built is on the methodology page.

Frequently asked questions

Is "onesie" a brand name?

Yes. Onesies® is a registered trademark that Gerber Childrenswear uses for its bodysuits ³. Cotokim says bodysuit, the generic name: a base layer that snaps between the legs, with short or long sleeves.

How many bodysuits for the first three months in total?

Sizes NB and 3M together, balanced amounts, laundry every two days, a dryer and a heated home: 5 short-sleeve and 5 long-sleeve bodysuits for mild months, and 9 short-sleeve and 2 long-sleeve for hot months.

Short sleeves or long sleeves?

It depends on the weeks your baby wears each size in your city. A baby born at the end of winter can wear size 3M in spring. The tool above does the math by season, and the list by city does it month by month.

What if I do laundry every day?

The count drops. Size NB, mild months, balanced, with a dryer: 8 pieces and 3 pairs of clothes doing laundry every day, 12 pieces and 5 pairs every two days and 16 pieces and 6 pairs every three days or more.

Should I skip size NB?

Not always. Babies grow at their own pace, and a bigger baby passes the size NB limits sooner on the same growth curves ¹. The list keeps a few NB pieces and leaves the rest to 3M. For a baby born small, Carter's size chart also has preemie sizes ⁴.

Do twins need twice as many?

Yes, clothes are per baby. For twins in size NB, mild months, balanced amounts: 24 pieces and 10 pairs.

Data sources

Our use of material from the Energy Information Administration, including links to its website, does not imply endorsement by the Energy Information Administration or the U.S. Government of Cotokim or its service.