Baby Clothing Sizes NZ: A Simple Guide

In New Zealand, baby clothing is sized 00000, 0000, 000, 00, 0, then 1 and 2. The numbers run backwards, so the more zeros a size has, the smaller the garment. Size 000 is the usual 0-3 month size, 00 is 3-6 months, and 0 is 6-12 months. From size 1 onwards, the number simply matches the child's age in years.

The part that catches most first-time parents out is that "newborn" and "0-3 months" are not the same size. Newborn on a label almost always means 0000, which fits up to about 4kg. 0-3 months means 000, which is a full size larger. Buy a pile of one thinking it is the other and you either end up with clothes that swamp a newborn or clothes that are outgrown before you leave the hospital.

Here is the whole system in one table, then the practical detail underneath.

NZ baby size chart

Size	Age guide	Weight guide	Also labelled as
00000	Premature	Up to 3kg	Prem, tiny baby
0000	Newborn	Up to 4kg	Newborn, NB
000	0-3 months	4-6kg	0-3M
00	3-6 months	6-8kg	3-6M
0	6-12 months	8-10kg	6-12M
1	12-18 months	10-12kg	1Y
2	18-24 months	12-14kg	2Y

Weight is the more reliable of the two guides. Age is an average, and averages do not dress a specific baby. If you know the weight, use the weight column and ignore the months.

Worth saying plainly: this numbered system is a convention, not a regulated standard. There is no NZ law setting what 000 must measure, so one brand's 000 can be a centimetre or two off another's. Treat the numbers as a starting point and the brand's own measurements as the answer.

Why "newborn" and "0-3 months" are different sizes

A newborn size (0000) is cut for a baby up to roughly 4kg. The average baby is born at around 3.3 to 3.5kg, so it fits, but not for long. Most babies are out of 0000 by about six weeks.

That is not a design flaw. It is just how fast babies grow. Whānau Āwhina Plunket notes that babies have growth spurts at two, four and six weeks, which is exactly the window 0000 covers. Three growth spurts inside one size explains why that beautiful newborn outfit got worn twice.

Size 000 is the size a baby actually lives in. It takes them from around 4kg to 6kg, which for most babies is roughly the first three months. If you are buying for a baby who has already arrived and is over 3.5kg, start at 000 rather than 0000.

Some brands, including us, skip the zeros entirely on baby sizes and label by months instead. Our baby range runs 0-3M, 3-6M, 6-12M, 1Y and 2Y, which maps to 000, 00, 0, 1 and 2, and the kids range continues from 3Y up to 8Y. So if you are looking for a 000 label on our site, it is 0-3M. We do it because months are easier to read at a glance when you are shopping tired, and because it removes the newborn-versus-000 confusion at the source.

How NZ sizing compares to European and US sizes

Our clothes are designed in Europe, so this comes up constantly for us. European baby sizing works in centimetres of body length, not zeros, which is genuinely a more useful system once you get used to it. US sizing uses months, but the months run larger than the NZ equivalents.

NZ size	European (cm)	US size
0000	50-56	Newborn
000	56-62	0-3 months
00	62-68	3-6 months
0	68-74	6-9 / 9-12 months
1	74-86	12-18 months
2	86-92	18-24 months

The mismatch to watch is at the 0 mark. NZ size 0 covers 6-12 months, but a US "6-9 months" and a US "9-12 months" are two separate sizes inside that same band. If you are buying from a US site, size up rather than down.

European sizing is worth understanding even if you never buy from Europe, because measuring your baby's length in centimetres gives you a number that works everywhere. It takes thirty seconds with a soft tape measure and it will save you more returns than any size chart will.

How fast babies actually move through sizes

Roughly:

• 0000 lasts about six weeks
• 000 lasts about three months
• 00 lasts about three months
• 0 lasts about six months
• 1 and 2 last about six months each

The pattern is that sizes get slower as they go. The first year is the expensive one because a baby moves through four sizes in twelve months, and then things settle down considerably.

Growth is not linear either, which is why health professionals plot it rather than guess it. Health New Zealand's Well Child growth charts track weight, length and head circumference from birth to five years, and your Well Child Tamariki Ora nurse will fill them in at each visit. If you want to predict what size your baby will need in two months, that chart is a better tool than any brand's age guide.

How much to buy in each size

This is the question behind the question. Our honest answer, based on what parents actually tell us they use:

0000 (newborn): four to six pieces, maximum. It is a six-week size. Borrow it if you can. If you are gifting, this is the size to avoid.

000 (0-3 months): this is where to spend. Six to eight bodysuits and onesies (see our baby girl and baby boy bodysuits), four to six sleepsuits, a couple of warmer layers. Babies in this size go through two or three outfit changes a day, so you need enough to survive a wet Auckland week where nothing dries.

00 and 0: five to six of each core item. Feeding is tidier by now and the laundry pile drops.

1 and 2: buy for the season rather than the size. A child in size 2 will wear it long enough that summer and winter both matter.

Two other things worth knowing. First, muslin wraps, bibs and headbands have no size at all, which makes the one-size pieces in our organic muslin range some of the few gifts that cannot be the wrong fit. Second, quality shows up most in the sizes that get worn hardest. A 000 bodysuit that keeps its shape wash after wash is worth more than three that go baggy at the shoulders by week four, because you will be washing it every second day.

If you are stocking up from scratch, our baby essentials collection is built around the pieces that get worn daily rather than the ones that get photographed once.

A few things that throw sizing off

Nappies add bulk. Cloth nappies especially. If you use cloth, size up on anything with a fitted waist or a crotch snap.

Sleepwear runs snug on purpose. Fitted sleepwear is meant to be close to the body. Do not size up to buy time.

Prem babies do not follow the chart. Sizing follows weight, not birthday, for the first year or so.

Cotton shrinks a little. Wash cold and dry flat and it will settle rather than shrink. Hot wash and hot dryer will take a size off almost anything.

Frequently Asked Questions

What size is 000 in baby clothes?

Size 000 is the 0-3 month size in New Zealand and Australia. It suits babies weighing roughly 4kg to 6kg. Most babies move into 000 at around six weeks old and stay in it until about three months.

Is newborn the same as 0-3 months?

No. Newborn on a NZ label means size 0000 and fits babies up to about 4kg. 0-3 months means size 000 and fits 4kg to 6kg. They are one full size apart, and newborn is the smaller of the two.

Should I size up in baby clothes?

For a first baby, buy true to weight in 0000 and 000, then size up from 00 onwards. Sizing up early means the neck and shoulders gape, which is uncomfortable and makes nappy changes harder. Sizing up later just buys you a few extra weeks of wear.

How do I know what size my baby is if I only know their age?

Use weight where you can, because it is far more accurate than age. If you only have age, use the chart above and check the brand's own measurements before you buy. A baby on the 90th percentile can easily be a size ahead of their age.

What baby sizes does Yes Mila stock?

Our baby range runs 0-3M, 3-6M, 6-12M, 1Y and 2Y, which is the equivalent of 000 through to size 2. The wider Yes Mila range carries on from there up to size 8. Product pages carry a size guide with garment length and chest in centimetres, and our FAQs also cover fit and returns.

Sizing is one of those things that feels complicated until someone lays it out once, and then it never bothers you again. Get the weight, match the size, and buy most of your 000.

Browse the Yes Mila baby range