Babies grow fast, especially in the first year. One month an outfit fits perfectly, and a few weeks later the snaps no longer close. Choosing the right size saves money, avoids returns and makes sure your baby is always comfortable.
This guide gives you a simple size chart, explains how to measure your baby, and shares tips for buying the right size online.
Why age is only a rough guide
Baby clothes are labelled by age, like 0 to 3 months or 6 to 9 months. But babies grow at different speeds. A big 2-month-old may already fit 3 to 6 months, while a small 4-month-old may still wear 0 to 3 months. That is why length and weight are better guides than age.
Baby clothes size chart (approximate)
| Size | Baby length | Baby weight |
|---|---|---|
| Newborn | Up to 56 cm | Up to 4 kg |
| 0 to 3 months | 56 to 62 cm | 4 to 6 kg |
| 3 to 6 months | 62 to 68 cm | 6 to 7.5 kg |
| 6 to 9 months | 68 to 72 cm | 7.5 to 9 kg |
| 9 to 12 months | 72 to 76 cm | 9 to 10 kg |
| 12 to 18 months | 76 to 83 cm | 10 to 11.5 kg |
| 18 to 24 months | 83 to 90 cm | 11.5 to 13 kg |
These are general ranges. Sizes vary between brands and styles, so always check the size details on the product page before ordering.
How to measure your baby
Length
Lay your baby on their back on a flat surface. Gently straighten the legs and measure from the top of the head to the heel. It is easier with two people.
Weight
Use the weight from your baby's last check-up, or weigh yourself holding the baby and subtract your own weight.
Chest (optional)
For tops and sweaters, measure around the fullest part of the chest, under the arms.
If your baby falls between two sizes, choose the larger one.
Tips for choosing the right size
Buy fewer newborn sizes
Many babies outgrow newborn size within a few weeks, and some never fit it at all. Buy just a few newborn pieces and more in 0 to 3 months.
Size up for winter
Winter clothes need room for a cotton vest underneath. If you plan to layer, go one size up for sweaters, rompers and outer layers.
Allow room for diapers
Rompers and bodysuits need space for a diaper. If a one-piece outfit is tight across the bottom or shoulders, it is time to size up.
Think ahead for the season
If you buy in October for a baby who is 2 months old, think about what will fit in December and January. A 3 to 6 months size may be the better choice.
Check the fit regularly
Signs an outfit is too small: snaps pull or will not close, sleeves or legs ride up, or the outfit leaves red marks on the skin.
Buying gifts? Choose a bigger size
Newborns receive lots of clothes in the smallest size. If you are buying a gift, choose 3 to 6 months or even 6 to 9 months so it can be worn later. Our Gift Sets make this easy.
Shopping at MiniKo
Each product page lists the size range the item fits. For example, our 3-Piece Romper Sets are made for 0 to 3 months, and our Daily Routine Baby Dress is designed for everyday comfort in the early months. Browse the full Clothing collection to find the right fit, and contact us if you are unsure which size to pick.
Frequently asked questions
What size should I buy for a newborn?
Buy a few pieces in newborn size and most items in 0 to 3 months. Many babies move out of newborn size within the first few weeks.
How long does a baby wear 0 to 3 months clothes?
Usually for about two to three months, but it depends on how quickly your baby grows.
Should I buy baby clothes one size bigger?
For winter layering, gifts and growing babies, yes. A slightly bigger size lasts longer and leaves room for a vest underneath.
Do all brands use the same sizes?
No. Sizes vary between brands and even between styles. Always check the size information on the product page.
Final thoughts
Measure your baby, go by length and weight rather than age, and size up when in doubt. With these simple habits, your baby's clothes will fit well for longer and you will spend less time on exchanges. Explore our Baby Boy and Baby Girl collections.