Baby grows with zips: sizes by height and how many you need

It's 3am, the nappy's leaked, and you're counting poppers in the dark. That's the moment most people go looking for baby grows with zips, and it's usually the moment they find us.

This is the page we send people to when they ask which size, how many, and what to put them in at night. Sizes are by length, not age, so there's a table. The TOG question has its own page, because it deserves one.

Key facts

• Our sizes run from Tiny Baby (up to 45cm) to 18 to 24 months (78 to 86cm), and every band is set by length, not birthday.
• The sleepsuits are 95% organic bamboo and 5% elastane, cut to fit up to two months longer than standard, and they wash at 30 degrees.
• The fold-over mitts are made for babies up to around 12 months; the fold-over feet stay useful for longer.
• The NHS says keep the room your baby sleeps in at about 16 to 20C, and that overheating raises the risk of SIDS.
• Hats and extra layers come off as soon as you come indoors or get into a car, bus or train, the NHS says, even if it means waking them.

What makes the best baby grows

A sleepsuit is a sleepsuit until you've done a week of night changes. Then you start noticing the things that matter: whether the zip opens from the bottom, whether the fabric breathes, whether the feet fold back, and whether it still fits a fortnight later.

Our list, in order: a two-way zip, a soft fabric that doesn't hold heat, fold-over hands and feet, and a cut with some room in it. Prints come last.

I'd take one good zip sleepsuit over three popper ones, and I say that as someone who likes the prints.

Zip baby grows vs poppers

Poppers are fine in daylight. At 3am, with a wriggling baby and a nappy that's leaked, they're a row of tiny decisions you don't want to make.

A one-way zip is better, but you still peel the whole suit down from the shoulders to reach the nappy.

Ours have QikZip™, a two-way zip that opens from the top or the bottom. Unzip from the ankle, change the nappy, zip straight back up. The top half stays on, they stay warm, and half the time they stay asleep.

Fold-over hands and feet, from newborn to crawling

Newborns scratch their own faces, and scratch mitts fall off. The fold-over mitts are part of the sleeve, so they can't. They're designed for babies up to around 12 months, though most people stop using them once the scratching stops.

The feet work as built-in socks, which means no socks lost in the pram. Once your baby is crawling, fold them back so they've got bare toes for grip on the floor, then fold them down again for the cot.

Soft baby grows, and what bamboo actually does

The first thing people say when they open the parcel is how soft it is. That's the bamboo. Ours is 95% organic bamboo with 5% elastane for the stretch, and it's softer against new skin than cotton, more breathable, and naturally hypoallergenic, which matters if your baby's skin is prone to eczema.

Bamboo is also naturally thermo-regulating. In plain words, it helps keep them warm on a cold night and cool on a warm one, rather than just adding a layer. It's a fabric, not a thermostat: the room temperature still does most of the work, and the NHS's 16 to 20C is the number to aim for.

They wash at 30 degrees, like everything else in the basket.

Baby grow sizes by height

Every brand puts an age on the label, and every baby ignores it. Length is what fits or doesn't, so measure your baby from the top of their head to their heel and use this table. It's the same one on our product pages.

The bands overlap on purpose. A 66cm baby is at the top of 3 to 6 months and inside 6 to 9 months, so take the 6 to 9: they'll be in it for longer, and a sleepsuit with room in it is comfier than one pulling at the shoulders. If in doubt, size up.

Ours are true to size and cut to fit up to two months longer than standard, so most people get more wear from a size than they expected. Tiny Baby fits up to 45cm and is the one for premature and very small babies.

0 to 3 months is the size most people order.

How many baby grows you need

More than you think in the first size, fewer than you think after that. Newborns get through changes at a rate nobody warns you about, and the washing machine can't keep up with two. We'd say four or five in the current size, plus a couple in the next size up so you're not caught out the week they grow.

Don't buy a drawer full in one size. They'll outgrow them long before they wear out, and the cut on ours is already generous. If your baby is 9 months, the sensible order is one in 9 to 12 and one in 12 to 18.

Dressing them for cold and warm days

The rule of thumb everyone gets told is one layer more than you're wearing. It's a starting point, not a law. The check that actually works is the Lullaby Trust's: feel your baby's chest or the back of their neck. Hands and feet are usually cooler, and that's normal. If the chest is hot or sweaty, take a layer off.

In cold weather, layers you can peel off beat one thick one. A vest, a sleepsuit, then a cardigan or a pramsuit for outside, and a hat for the street. The NHS says take the hat and the extra layers off as soon as you come indoors or get into a car, bus or train, even if it means waking them.

In warm weather, a single layer is usually enough indoors, and in a heatwave a vest on its own is fine. Babies don't need hats indoors, and overheating raises the risk of SIDS, so if you're unsure, go cooler.

Baby grows at night, and the sleeping bag question

At night the sleepsuit is the layer next to the skin, and the sleeping bag goes over it. The NHS says to use lightweight blankets, sheets or a baby sleeping bag, and to keep pillows and loose bedding away from your baby.

A sleeping bag can't be kicked off or wriggled under, which is why most people switch to one and stop thinking about blankets.

What goes under the bag depends on the room temperature and the bag's TOG, and that's a table of its own. Our baby sleeping bag guide has it, temperature by temperature, with the sizes. Two rules travel with you: never add a blanket on top of a sleeping bag, and if you can pull the bag over your baby's head with the zip closed, it's too big.

Funky baby grows, prints and plains

Once the practical boxes are ticked, buy the print you like. The Oatmeal ribbed and the Tulip are the same bamboo, the same zip and the same sizing; the difference is the print. The sleepsuit collection has the patterned ones and the plain ribbed ones in one place.

Matching kids pyjamas

If there's an older one at home, our kids pyjamas are made in the same soft bamboo, in sizes for toddlers and older children, so the two of them can match without the big one being in a sleepsuit.

Questions we get asked

What size baby grow does a 66cm baby need?

6 to 9 months in ours, which covers 63 to 71cm. The 3 to 6 months tops out at 66cm, so they'd be out of it within weeks. When your baby sits at the top of a band, take the next one up.

Are baby grows with zips better than poppers?

For night changes, yes, and it isn't close. A two-way zip opens from the feet end, so the nappy gets changed without the top half coming off. Poppers have their place in the daytime, when you've got both hands and the light on.

Are bamboo baby grows warm enough for winter?

Yes, with the right sleeping bag over them. Bamboo breathes and helps regulate temperature rather than trapping heat, so the warmth comes from the TOG of the bag and the temperature of the room. Our sleeping bag guide matches the two.

Can my baby wear a sleeping bag over a baby grow?

Yes, that's the normal setup. What goes under the bag depends on the room temperature and the bag's TOG, and nothing goes on top. Check the back of their neck rather than their hands; hands are always cooler.

How many baby grows does a newborn need?

Four or five in the current size and a couple in the next one up. They'll grow out of them before they wear out.

Is a baby grow the same thing as a sleepsuit?

Yes. Baby grow, babygrow, sleepsuit and onesie all get used for the same one piece suit with legs. A bodysuit or vest is the short one without legs that goes underneath.

Next step: the zip sleepsuit collection has every size from Tiny Baby up, and the sleeping bag guide sorts out what goes over it at night.

This is general guidance from the BABYGO® team, not medical advice. Your health visitor or GP knows your baby; ask them if anything here doesn't fit your situation.