Baby Clothing & Fashion

Newborn Baby Clothes Sizes and Tog Guide UK

Q: What size clothes does a newborn actually need?

Most newborns start in newborn size (up to about 7.5 lb / 3.4 kg) or 0 to 1 month. Babies over 8 lb often skip newborn and go straight to 0 to 3 months. First size (tiny baby) is only needed for babies under about 5.5 lb. Buy a mix of newborn and 0 to 3 months rather than stocking up on one size, as growth is rapid in the first weeks.

Q: How many sleepsuits and bodysuits does a newborn need?

A practical starting point is 6 to 8 sleepsuits, 6 to 8 short-sleeve bodysuits, 2 to 3 cardigans, plus hats, socks and scratch mittens. You will wash daily in the early weeks, so this number lets you cope with sick and nappy leaks without running out. Add more once you know your baby's size and how often you want to do laundry.

Q: What tog should a newborn wear at night?

Tog is a measure of warmth and the right choice depends on room temperature. The Lullaby Trust advises a room temperature of 16 to 20 degrees C for sleep. As a guide: at 16 to 18 degrees use a 2.5 tog sleeping bag, at 18 to 21 degrees use 1.0 to 1.5 tog, at 22 degrees or higher use 0.5 to 1.0 tog. Always check your baby's chest or back of neck, they should feel warm not hot, and never use loose blankets as an alternative to a sleeping bag.

Q: Should you wash newborn clothes before the first wear?

Yes. New clothes can carry chemical finishes, dyes and dust from manufacturing and shipping that irritate newborn skin. Wash everything before the first wear at 30 to 40 degrees C with a fragrance-free, non-biological detergent, and skip fabric softener. This is the same routine recommended for muslins and bedding.

Q: What fabrics are safest for newborn clothes?

Look for soft, breathable fabrics, ideally 100 percent cotton or cotton blends certified to OEKO-TEX Standard 100. Avoid clothes with loose buttons, ribbons, cords or small appliques that could detach, and check that neck openings are wide enough that fabric does not press on the face. Flame-retardant nightwear is only relevant for older babies, newborn sleepsuits should be close-fitting for safety.

Q: When should you size up in baby clothes?

Size up when seams pull, poppers strain, feet press against the end of sleepsuits, or cuffs leave marks. Weight and length matter more than age on the label. If your baby is long or broad, you may size up even though the age range says they should still fit. Second-hand clothes are fine if they have no loose parts and are washed before use.

By Emma Clarke · 5 September 2026 · 6 min read

The short answer: most UK newborns live in newborn and 0 to 3 months for the first few weeks, you need about 6 to 8 sleepsuits and the same in bodysuits to stay ahead of washing, and what your baby wears at night should follow room temperature rather than a fixed tog. The Lullaby Trust advises a sleep room of 16 to 20 degrees C and checking the chest or back of the neck to judge warmth. A room thermometer that you trust makes clothing choices quicker than guessing, and everything should be washed before first wear with a fragrance-free, non-biological detergent.

🔑 Key Takeaways

Buy two sizes, not one: a handful of newborn plus a larger batch of 0 to 3 months covers most birth weights without waste
6 to 8 sleepsuits and 6 to 8 bodysuits is the practical starting number for daily washing
Dress for the room, not the age label: tog follows temperature, with 2.5 tog at cooler temps and 0.5 to 1.0 tog when warm
Fabric and fit matter: soft cotton, no loose trims, wide neck openings, and poppers you can do one-handed at 3am

Shopping for newborn clothes is where the list anxiety hits. Labels say newborn, first size, 0 to 1 month, 0 to 3 months, and none of them line up neatly with the weight your midwife is estimating. Add tog in the sleeping bag aisle and it is easy to spend too much on the wrong sizes.

This guide keeps it focused on what UK parents actually need: how sizes map to weight and length, how many of each item to buy, how to use tog and room temperature to dress for sleep safely, which fabrics to favour, and the small fitting details that make life easier when you are dressing a wriggly baby at night. If you want a deeper dive on washing and detergent we have a separate newborn laundry guide, and for safe sleep more broadly see our sleep safety guide.

Newborn clothes sizes in the UK: what the labels really mean

UK baby clothing does not use one standard chart. Each brand measures slightly differently, but the weight ranges are fairly consistent.

Tiny baby / first size is for babies born early or under about 2.5 kg (5 lb 8 oz). Most full-term babies skip this entirely, so only buy a couple if a scan suggests a smaller baby. Newborn generally fits up to about 3.4 kg (7 lb 8 oz) and suits babies from roughly 45 to 58 cm long. 0 to 1 month overlaps newborn but often runs a touch longer in the body, good for babies who are thin and tall. 0 to 3 months fits from about 3.4 to 6 kg and is the size most babies wear longest in the first weeks, especially those born over 3.6 kg.

The age on the label is the least useful part. Go by weight and length, and check the garment measurements where the shop lists them. A tall, slim baby may need 0 to 3 months in length while still swimming in the width, a chunkier baby may fill newborn quickly. If you are stocking up before birth and do not know the birth weight, buy a starter pack split roughly one-third newborn, two-thirds 0 to 3 months, and keep receipts. You will know within a week which size is actually right.

Second-hand clothes are a sensible way to handle this uncertainty. Check for loose buttons, detached appliques, stretched necklines that ride up over the face, or elastic that has gone slack. If the seams and poppers are sound, a wash before use is the only prep needed.

How many sleepsuits, bodysuits and extras you actually need

Newborns produce a surprising amount of laundry. Sick, nappy leaks and dribble mean even a good day can use two sleepsuits.

Sleepsuits: 6 to 8. Choose front-opening, popper-through styles with built-in feet and optional fold-over scratch mitts. Envelope necks are less common in sleepsuits now, popper shoulders are more practical for head clearance.

Short-sleeve bodysuits (vests): 6 to 8. These go under sleepsuits for warmth and keep nappies in place. Envelope shoulders make them easy to pull down over the body rather than up over the head after a blowout.

Cardigans or zip jackets: 2 to 3. Cotton for indoors, a slightly thicker knit for going out. Avoid hoods on anything worn for sleep.

Hats, socks, mittens: 1 to 2 hats for outside, 3 to 4 pairs of socks, and 2 pairs of scratch mittens if your sleepsuits do not have them built in. The NHS what you will need list also includes muslins, nappies and bedding, which matter as much as the fancy outfits that never get worn.

Do not buy a full wardrobe in newborn size. You will wash every day or two, so the numbers above let you rotate without stress. Once your baby is here and you know whether they are long, compact or somewhere in between, topping up in the right size is quick.

Tog and temperature: dressing for sleep without overheating

Tog is just a measure of how warm something keeps your baby. It does not replace checking the room.

The Lullaby Trust safe sleep guidance advises a baby's sleep room stays between 16 and 20 degrees C. The NHS does not set a precise room figure but advises that babies should not overheat and that you check them regularly. In practice, most UK homes sit in that range with a little seasonal drift.

As a simple guide for what to dress your baby in at night, using a sleeping bag rather than loose blankets:

16 to 18 degrees C: 2.5 tog sleeping bag, plus a long-sleeve bodysuit and sleepsuit underneath
18 to 21 degrees C: 1.0 to 1.5 tog sleeping bag, plus a bodysuit and sleepsuit or just a bodysuit if warm
22 degrees C or higher: 0.5 to 1.0 tog bag, bodysuit only, and no extra layers

This is a starting point, not a rule. Feel your baby's chest or the back of their neck. Warm, not hot or clammy, is right. If their tummy feels hot or they are sweating, remove a layer even if the chart says otherwise. Hands and feet often feel cool and are not a reliable guide. Loose blankets, duvets and pillow-like bumpers should not be used for babies under 12 months, a well-fitted sleeping bag is the safer alternative.

A reliable room reading makes these choices quicker than holding your hand up and guessing. Many parents keep a Tommee Tippee GroEgg2 colour-changing thermometer on the nursery shelf because the colour gives an at-a-glance cue when you are half awake, or a simple Dreambaby Room and Bath Thermometer Duck if you want a portable option that works for bath water too. For a numerical reading that you can check across different rooms, the ThermoPro TP55 digital thermo-hygrometer is widely used in UK nurseries, and the DOQAUS Room Thermometer 3-pack lets you keep one in the bedroom, one in the living room and one by the changing area without moving it around. The Angelcare Happy Seal bath and room thermometer is another bath-to-bedroom option if you prefer a sealed, floating design for the tub.

Fabric, safety and small details worth checking

Fabric: 100 percent cotton or a cotton blend is the everyday workhorse, soft, breathable and easy to wash. If you like certifications, OEKO-TEX Standard 100 means the finished fabric has been tested for common harmful substances. Organic cotton is a nice to have rather than a must have, and it still needs the same pre-wash.

Fit and fastenings: Look for wide, stretchy neck openings that clear the face easily, flat seams that sit smooth against skin, and poppers that run the full length of the leg or across the shoulder. Zips are fast but check for a fabric guard behind the zip head so it cannot nip. Avoid drawstrings, ribbons and loose cords on anything your baby wears, and be wary of small decorative elements that could come away.

Sleepwear specifics: Newborn sleepsuits and sleeping bags should be close-fitting enough that fabric does not ride up over the face. Flame-retardant labelling on children's nightwear is aimed at older, looser garments, the safer move for newborns is simply a snug, age-appropriate fit and no added loose layers.

Washing before first wear: Wash all new clothes at 30 to 40 degrees C with a fragrance-free, non-biological detergent. Skip fabric softener, it coats fibres and can irritate sensitive skin. Our how to wash newborn clothes guide covers temperature, detergent choice and stain removal in more detail.

When to size up

The label age is not the signal, the fit is. Size up when poppers pull, seams leave marks, feet push against the end of sleepsuits, or the neck sits tight when you lift. Length is often the first clue, if you are stretching a sleepsuit to close the poppers, it is time. Many parents find they size out of newborn within one to two weeks, especially for babies born over 3.6 kg, while 0 to 3 months lasts four to eight weeks. Keep one or two sleepsuits in the next size up in the drawer so you are not caught short mid-nappy change.

Frequently Asked Questions

What size clothes does a newborn actually need?

Most newborns start in newborn and 0 to 3 months. Buy a small number of newborn for the first days and a larger number of 0 to 3 months, especially if your baby is estimated over 8 lb. Weight and length matter more than the age on the label.

How many sleepsuits and bodysuits does a newborn need?

Plan for 6 to 8 sleepsuits and 6 to 8 short-sleeve bodysuits, plus a couple of cardigans and the small extras like hats and socks. This covers daily washing with enough spare for sick and nappy leaks.

What tog should a newborn wear at night?

Choose tog by room temperature, not by age. The Lullaby Trust suggests 16 to 20 degrees C for the sleep room. Around 16 to 18 degrees use 2.5 tog, 18 to 21 degrees use 1.0 to 1.5 tog, 22 degrees and above use 0.5 to 1.0 tog. Check the chest or back of the neck to confirm your baby feels warm, not hot.

Should you wash newborn clothes before the first wear?

Yes. Manufacturing finishes, dyes and dust can irritate newborn skin. Wash at 30 to 40 degrees C with a fragrance-free, non-biological detergent and no fabric softener before the first wear.

What fabrics are safest for newborn clothes?

Soft, breathable cotton, ideally OEKO-TEX Standard 100 certified, with no loose buttons, ribbons or cords. Wide neck openings and full-length poppers make dressing easier and reduce fabric near the face.

When should you size up in baby clothes?

When seams pull, poppers strain, feet press the ends of sleepsuits, or cuffs leave marks. If you have to stretch a garment to fasten it, move up a size, even if the age range says it should still fit.

For more on dressing and safe sleep, explore our room temperature guide and sleeping bag picks, or return to My Baby Now.

Emma Clarke

Emma reviews baby gear for My Baby Now, prams, car seats, monitors, toys and everything in between. Parent of two, she has first-hand experience of what actually matters when you are navigating sleep deprivation and a screaming baby in a car park.

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Last reviewed: 5 September 2026 · Evidence-based content · Contains affiliate links