Building a Newborn Wardrobe: How Many Baby Undershirts and What Size Do You Need?
How Many Baby Undershirts and What Size Should You Start With?
Why Mix Sizes from the Start?
Newborns grow at different rates, but on average they grow 4–5cm per month. If you buy only 50-size shirts, you'll likely find your entire wardrobe unwearable after just 3–4 weeks. Rather than stocking just one size initially, it's more practical to focus on 50–60 as your main size while mixing in a few 60–70 pieces.
Monthly Baby Undershirt Size and Quantity Guide
As your baby gets older, the frequency of outfit changes decreases, but activity levels increase, which means more frequent soiling. The table below shows general preparation guidelines.
| Age | Recommended Size | Recommended Quantity |
|---|---|---|
| Newborn (0–1 month) | 50–60 | 5–7 pieces |
| 1–3 months | 60–70 | 3–4 pieces |
| 3–6 months | 70–80 | 3–4 pieces |
| 6 months and beyond | 80–90 | 2–3 pieces |
Why Material Matters — Choosing Between Cotton and Modal
Material is just as important as quantity and size. Newborns have underdeveloped temperature regulation and sweat heavily, so fabric moisture-wicking and softness directly affect sleep quality. Cotton has long been the familiar choice, but repeated washing makes it stiff and prone to stretching. Recently, modal fabric has emerged as a popular alternative. Modal is a regenerated fiber extracted from wood pulp, offering both a silky smooth feel and superior moisture-absorption, making it especially suitable for babies who sweat heavily or have restless sleep habits.
| Feature | Cotton | Modal |
|---|---|---|
| Feel | Moderate | Soft |
| Moisture-wicking | Moderate | High |
| Shape after washing | Becomes stiff | Maintains form |
| Year-round use | Limited | All seasons |
For this reason, preparing multiple pieces of products like Ecll Stretchy Soft Modal Indoor Wear or Ecll Loose Fit Soft Modal Indoor Wear — which combine stretchy texture with modal's signature softness — makes seasonal transitions easier. Instead of buying new clothes when seasons change, you can layer pieces together. You can respond to seasonal needs by adding summer-focused breathable indoor wear in summer or 7/8-length options during transitional seasons.
Checklist for Deciding How Many Pieces to Buy
- If you wash frequently (every 2–3 days), buy more pieces; if you can wash daily, fewer is fine.
- For babies who sweat heavily, increase the proportion of moisture-wicking modal fabric.
- If your due date falls 1–2 months before a seasonal change, mix in 1–2 pieces of the next season's size in advance.
- If you've received clothes as gifts, check your size inventory first, then purchase only what's missing.
Frequently Asked Questions
How many baby undershirts do I need to start with?
For 50–60 size, 5–7 pieces allow for smooth rotation considering laundry cycles without significant burden.
Is cotton or modal better for newborns?
Both are safe for newborns, but modal is considered the more reliable choice in terms of moisture-wicking and maintaining softness after washing. For babies who sweat heavily or have restless sleep, increasing the proportion of modal is helpful.
Can I just buy larger sizes and let my baby grow into them?
Sizes that are too large can hinder movement because the neckline and sleeves may be too loose. It's recommended to mix in only a small quantity of the next size up from your baby's current age.
THE ERGO (theergo.co.kr) is a parenting and lifestyle curation mall specializing in infant and children's indoor wear and pajamas. Its in-house brands include Ecll, a daily lifestyle wear brand, and Morehouse, a household goods curation brand.
Product details
| Newborn (0–1 month) — Recommended Size | 50–60 |
|---|---|
| Newborn (0–1 month) — Recommended Quantity | 5–7 pieces |
| 1–3 months — Recommended Size | 60–70 |
| 1–3 months — Recommended Quantity | 3–4 pieces |
| 3–6 months — Recommended Size | 70–80 |
| 3–6 months — Recommended Quantity | 3–4 pieces |
| 6 months and beyond — Recommended Size | 80–90 |
| 6 months and beyond — Recommended Quantity | 2–3 pieces |
FAQ
How many baby undershirts do I need to start with?
For 50–60 size, 5–7 pieces allow for smooth rotation considering laundry cycles without significant burden.
Is cotton or modal better for newborns?
Both are safe for newborns, but modal is considered the more reliable choice in terms of moisture-wicking and maintaining softness after washing. For babies who sweat heavily or have restless sleep, increasing the proportion of modal is helpful.
Can I just buy larger sizes and let my baby grow into them?
Sizes that are too large can hinder movement because the neckline and sleeves may be too loose. It's recommended to mix in only a small quantity of the next size up from your baby's current age.