Baby Clothes Size Chart Australia: Newborn to 12 Months (00000 to 0)

Australian baby clothes run on a numeric sizing system. Rather than age labels like "0 to 3 months", you'll see 00000, 0000, 000, 00 and 0 on the tags of nearly every piece of Australian newborn clothing, covering premmie bubs through to 12 months.

Those numbers map to a combination of weight and length, not age alone. Two babies the same age can be a full size apart, so the numbers describe the baby's actual measurements rather than a birthday.

This guide covers the full newborn-to-12-month range, sizes 00000 to 0. If you're used to US, UK or EU sizing, there's a conversion table further down.

Baby Clothes Size Chart: 00000 to 0

Here's the master chart. Weight and length ranges are typical guides, and individual brands publish their own thresholds, so treat these as your starting point rather than exact rules.

The quick answers, since these are the questions parents search most:

• What size is 00000? Premmie or tiny baby, up to around 2.5 kg.

• What size is 0000? Newborn, up to around 4 kg.

• What size is 000? 0 to 3 months, roughly 4 to 6 kg.

• What size is 00? 3 to 6 months, roughly 6 to 8 kg.

• What size is 0? 6 to 12 months, roughly 8 to 10 kg. Yes, really. In Australian sizing, 0 covers the second half of the first year, and it catches out almost everyone the first time.

The numbers keep climbing past the first birthday. Size 1 covers roughly 12 to 18 months, then 2 and 3 track the toddler years, so the logic continues even though this guide stops at 12 months.

How Australian Baby Sizing Actually Works

Babies of the same age vary enormously. A three-month-old on the 90th weight percentile can be a kilogram heavier than one on the 10th, and that gap is the difference between size 000 fitting and straining at the poppers.

That's why the AU system anchors to weight and length. The practical rule: choose by your baby's current weight and length first, then use age as the tiebreaker if they sit between sizes.

Percentiles matter here in a simple, reassuring way. A bub tracking on a higher weight or height percentile will move into the next size earlier than the age label suggests, and one on a lower percentile will stay in each size longer. Neither is a problem. The chart just gets read through your baby, not the other way around.

One more distinction worth understanding: the newborn cut versus the raw measurements. Newborn pieces are shaped for newborn bodies, with nappy room built in and features like fold-over cuffs, so a 0000 isn't simply a shrunken 00. Fit comes from both the measurements and the cut.

How to Measure Your Baby for the Right Size

1. Measure length crown to heel.

Lay your baby flat on a soft surface with their head straight and legs gently extended, and run a soft measuring tape crown to heel.

2. Get their current weight.

Use the most recent figure from your child health nurse visit, or weigh yourself holding bub on home scales and subtract your own weight.

3. Read the chart with both numbers.

A worked example: a bub weighing 8 kg and measuring 70 cm has moved past the 00 thresholds on both counts, so size 0 is the pick.

4. Between sizes, round up.

Especially for fast growers. A slightly roomy outfit gets worn for months; a snug one gets worn twice.

5. Size up in a few specific situations.

When a growth spurt is clearly underway, when you use cloth nappies (they need extra room through the seat), and when you're layering for the cooler months and need space for a singlet underneath.

Fit changes fast in the first year, so it helps to know the exit signs too. Our guide to when to size up baby clothes covers the signals an outfit has been outgrown, which pairs naturally with the chart above: this page answers what size, that one answers when to move.

Choosing Sizes When Buying or Gifting

The right call depends on which buyer you are. Three common situations, three approaches.

Buying before the baby arrives: start at 000.

Many parents skip 0000 almost entirely, because an average-sized newborn can pass the 4 kg mark within weeks. Keep one or two 0000 pieces for the very first days, like a Take Me Home Bundle for the trip home from hospital, and put the rest of the budget into 000 and up.

Gifting without measurements: size up and think a season ahead.

A bub born in May will be wearing size 00 through spring, so a 00 in a spring-appropriate weight lands right when it fits. Browsing gift sets sized for later months sidesteps the problem entirely, since the parents will have plenty of newborn pieces already.

Deciding how much to buy: a few pieces per size.

Babies move through the early sizes quickly, sometimes in six to eight weeks, so a handful of well-chosen pieces per size beats a drawer full of one size. Multi-packs like the Textured Knit Bodysuit Trio are a practical answer, and our newborn clothes essentials guide breaks down how many growsuits, singlets and bodysuits each size realistically needs.

Why Sizes Vary Between Brands

A 000 in one brand won't always match a 000 in another. Cut, fabric stretch and each label's fit philosophy all shift where a size lands. Among the reference points Australian parents already know, Bonds and Marquise are widely regarded as running big and wide, while Purebaby and other organic-leaning labels cut slimmer and closer to the stated measurements.

Stretch matters as much as cut. A jersey bodysuit with plenty of give forgives a borderline size call; a structured woven piece won't. The same numeric label can behave quite differently across the two.

The fix is the same everywhere: check the individual brand's published size guide before you buy, particularly before bulk-buying. 

Every label measures its own garments, so the brand's chart always beats the generic one, including ours. If you're comparing pieces across our newborn girls onesies or newborn boys onesies, the size guide on the product page is the number to trust.

Converting International Sizes to Australian

US and UK brands label by age, and EU brands label by height in centimetres. Both convert cleanly onto the AU chart because they describe the same babies.

EU sizing is often the most precise cross-reference, since it's built directly on height rather than an age estimate. If you know your baby measures 68 cm, an EU 68 will fit regardless of what the age label claims.

The main trap when converting: a US "12 months" garment corresponds to AU size 0 territory, not AU size 1. Match on the weight and length behind the label, not the number printed on it.

Baby Shoe and Accessory Sizing Basics

Shoes and hats run on their own systems, separate from clothing sizes. Pre-walker shoes are sized by foot length in centimetres, typically spanning about 9 to 12 cm across the first year. Hats and beanies go by head circumference, usually around 36 to 48 cm between birth and 12 months.

Both are quick to measure at home with a soft tape. When in doubt, size up on headwear too.

Common Baby Sizing Mistakes to Avoid

1. Buying by the age label alone, then discovering the outfit fits in the wrong season

2. Stocking up on 00000 and 0000, which most babies wear for only a few weeks, if at all

3. Ignoring weight and length when your baby sits on a high or low percentile

4. Assuming size 0 means newborn (it's 6 to 12 months in Australia)

5. Bulk-buying without checking that brand's specific size guide first

6. Forgetting fit is about length too: a long, average-weight bub outgrows by height first

Weight and Length Beat the Age Label

Everything in this guide reduces to one habit: measure your bub, then read the chart, then check the specific brand's guide before you buy. Weight and length decide the fit. The age on the label is only ever the rough sketch.

Get that habit early and the numeric system becomes an advantage rather than a puzzle. You'll buy fewer pieces that never get worn, gift with confidence, and know exactly why that size 0 growsuit is waiting patiently in the drawer for month six.