Sizing Up for Black Friday: How to Buy for Next Year's Growth

Every parent has a version of the same drawer: the jacket bought "to grow into" that swamped them in November and was too short by March, and the leggings bought to fit perfectly that were halfway up the shin by spring. Buying ahead for children is a guessing game about the future, played with a tape measure and a little hope.

It gets easier with a few rules. Some pieces should be bought to fit today, some can safely go one size up, and one or two should never be sized up at all. This guide is about buying kids clothes a size up — when it is smart, when it backfires, and how to get it right when you are buying for the months ahead rather than just the week.

Start with today's measurements, not age

Age labels are a starting point and nothing more. Two seven-year-olds can be three sizes apart, and brands do not agree with each other about what "7" means. Before buying anything, measure height, chest and inside leg, and compare them to a size chart rather than to the label in last year's jacket.

Our kids size conversion chart turns those measurements into sizes across regions, and the activewear sizing guide explains how technical clothing should fit differently from everyday clothes. It takes five minutes, and it is the difference between a purchase that works and one that goes back.

How much do children actually grow?

Roughly, school-age children tend to grow around five to six centimetres a year, often in bursts rather than evenly — a quiet six months and then a sudden change over a summer. For buying ahead, that means a window of four to six months is usually safe to plan for, while a full year is a gamble. Most clothes have enough tolerance to absorb a few centimetres; very few absorb a whole year.

The practical reading: if your child sits in the middle of their current size, buy that size for winter. If they are at the top edge — sleeves already near the wrist, waistband already snug — buying up is reasonable for anything you want to last into spring.

Size up or true to size

Here is how the main categories break down.

• Base layers: true to size, always. The layer against the skin only works if it touches the skin, because that is how it moves sweat away. A loose base layer leaves gaps where cold air sits and damp collects. This is the one category never to buy big.
• Leggings and fitted bottoms: true to size. A legging that slides down is worse than one that is slightly short. Stretch fabrics like the Cloudie Essential Infinity Leggings, with 360° stretch, already give a generous growth window without going up a size.
• Relaxed bottoms: up is fine. Sport pants and joggers with an elastic waist and cuffs, like the Glow Fleece Sport Pants, tolerate a size up well — the cuff stops the extra length becoming a trip hazard.
• Mid layers: up is usually fine. A fleece or hoodie worn over a base layer can take a little extra room, as long as the sleeves do not cover the hands.
• Outer jackets: up only if they are at the edge. A jacket needs room for a layer underneath, which a well-fitting one already has. Going up a size on a child who is mid-size gives you flapping cuffs and cold air at the hem.
• Shoes: never up more than a thumb's width. More on this below.

The jacket test

Winter jackets are where sizing up most often goes wrong, because the instinct to make an expensive item last is strong. Before deciding, put the jacket on over the mid layer your child actually wears and check three things: they can reach both arms forward without the back pulling tight, the sleeve ends at the wrist bone rather than past the knuckles, and the hem covers the lower back when they bend down.

If all three pass in the current size, that is the right size, even if it feels like it will not last. Insulated pieces like the Primaloft Puffer Jacket are cut with room for layering already; adding a size on top of that removes the warmth you paid for, because insulation works by trapping air close to the body. For full snow gear, the same rule holds — a snowsuit that is too long gathers at the ankle and lets snow in.

Shoes are the exception to every shortcut

Feet do not grow on a timetable, they rarely grow evenly, and a shoe that is too big changes how a child walks and runs. The right amount of room is roughly a thumb's width — about a centimetre — between the longest toe and the end of the shoe, measured standing up at the end of the day when feet are largest.

Buy shoes for the next few months, not the next year, and measure both feet, because they are often slightly different. Our kids' shoe size chart walks through measuring at home, and the shoe size chart gives exact lengths for each size.

If you get it wrong

Even with good measurements, some purchases will not fit. Keep tags on and packaging until the item has been tried on properly, with the layers it will be worn over. Our returns and exchanges policy sets out the window and conditions — items need to be unworn and unwashed with tags attached — so try things on at home soon after they arrive rather than saving them in a cupboard.

It also helps to buy across a family in one go and swap sizes between siblings before anything is worn. The best-fitting wardrobe is usually the one that was tried on, adjusted and settled within the first week.

Frequently asked questions

Measure first, buy close-fitting layers to fit today, let the relaxed pieces carry the growth, and give shoes no more than a thumb's width. The everyday pieces that fit across a long season are in best sellers.