10 best kids’ thermals and base layers that will keep them warm and cosy

Ticking all our boxes for warmth, style and softness, this great value set from Roarsome is the ultimate multi-tasker. They were a clear favourite with our testers who loved the simple cut and silky-soft material – and they performed perfectly as breathable base layers when out hiking, as well as running in a very cold cross-country race. There was no overheating or clamminess, just the right amount of insulation. Stylish and comfy enough to double as pyjamas and general loungewear at home, they have been worn on repeat since we began testing.

Made from sustainable, premium bamboo – great for naturally regulating the body temperature as well as being hypoallergenic –  we found these to be such a brilliant choice for children who declare most fabrics “itchy”. They are also really easy to machine wash and tumble dry, with no need for special detergents or machine settings. These base layers are buttery soft and come in an assortment of colours, with sizes ranging from age one to 10. We think the Roarsome base layers offer serious value for money and are worth every penny.

Simple yet effective, these thermals from Damart are great for keeping younger kids cosy. You can pick the level of warmth needed – we tested out level three, which is medium warmth, designed for winter wear. Our younger tester was kept nice and toasty at home and when out and about. The material itself is very soft and lightweight enough to layer under clothes for forest school or outdoor nursery, with sizes ranging from two years up to 14.

The set is a breeze to machine wash and tumble dry, without any shrinkage or bobbling. Both the top (£15, Damart.co.uk) and leggings (£15, Damart.co.uk) make a handy addition to any child’s winter wardrobe.

Made from 100 per cent merino wool, these stylish base layers got the no-itch seal of approval from our testers, who loved the soft feel. With flatlock seams and no annoying label at the neck, they scored high for comfort and the lightweight material makes these a perfect choice for low-bulk, winter sports base layers. However, the cool styling details, like the logo-print elasticated waist and blaze orange colourway, made these a massive hit for simple everyday wear as well.

The moisture-wicking and breathability were put to the test climbing fells in the Lake District and were suitably impressed. Everything about the top (£45, icebreaker.com) and leggings (£45, icebreaker.com) feel premium and, even after machine washing (we used the wool cycle and wool detergent) and line drying, they have retained that exceptionally soft feel. Yes, they are an investment price-wise, but these thermals are designed to last and be passed down the family – the quality is undeniable.

We love the clever two-in-one design of these base layers which have a merino wool exterior (for insulation) and Helly Hanson’s unique super-soft fibres next to the skin, to wick away moisture and help regulate the wearer’s temperature. Our five-year-old tester loved the softness of this set and has declared them her favourite “comfies” – the fact they come in a hot pink camo design certainly helps too.

Fit details, such as the dipped hem at the back of the top, wide cuffs and fleecy reinforced knees, all upped the comfort factor. The cut is snug, yet stretchy, making it ideal for layering – although when base layers look this fancy it almost feels a waste to hide them away.

If you’re after extra warm base layers on a budget, it’s hard to beat this top (£16.99, Mountainwarehouse.com) and pants (£16.99, Mountainwarehouse.com) set from Mountain Warehouse. Cosy, while still being lightweight and breathable, and with all the antibacterial and moisture-wicking features you’d expect.

We put these to the ultimate test on a family holiday to Lapland. Worn under another layer and snowsuit, these kept our four-year-old and seven-year-old testers at the perfect temperature – never too hot or too cold – even in -24C. They pass the no-itch test, no problem, and work really well as toasty pyjamas or comfy clothes to wear around the house. The raglan sleeves and contrasting cuffs and stitching definitely earn some style points too.

So much more than simple thermals, these super luxurious and soft merino layers from independent British brand Smalls Merino deliver next-level comfort and style. The foldable cuffs and drawstring waist of the trousers (£79, Smallsmerino.co.uk) help achieve the perfect fit, while the thoughtful addition of pockets made these an absolute favourite with our little testers. Our eight-year-old tester lives in his Smalls set now.

We also love the brand’s dedication to only using ethically made and fully traceable merino wool with sustainability and workers’ rights at its heart. While these thermals aren’t cheap, the quality is outstanding and the eco-friendly ethos makes the investment worthwhile.

These may be the thinnest thermals we tested, but they still provided plenty of warmth, keeping our little tester toasty at home and as base layers for outdoor adventures. Made from merino wool, the T-shirt (£34.95, Wheat.co.uk) and leggings (£29.95, Wheat.co.uk) set is lightweight and sit gently on the skin, with no itchiness reported by our five-year-old. Thanks to the featherlight feel, these are a great choice if your child doesn’t like bulky layers or is particularly active and hates to be restricted by clothing. We’ve washed on a wool setting in the machine, and they’ve come out looking as new.

What makes these stand out from the others in our round-up is the stylish choice of colours and patterns. We loved the Scandi-chic florals and stripes, which elevate these from basics to layers you want to show off.

These well-made separates from PO.P are a brilliant option if you’re looking for decent all-rounders. The merino fabric makes them thin, lightweight and flexible enough to wear as winter sports base layers or just as an additional layer of cosiness on cold days.

Breathable, antibacterial and anti-odour, our testers have worn these many times and we still haven’t needed to put them in the machine (on a wool cycle) thanks to the natural self-cleaning properties of the wool – we’ve found simply hanging them up to air has done the trick.

Foldable cuffs and plenty of stretch guarantee a good fit wherever your child sits in the age range. Available in six colours and in a simple classic cut, these are designed to be worn, enjoyed and passed down through the family.

Comfortable, durable and breathable, these fun base layers from Muddy Puddles are just the thing for keeping active kids cosy and unrestricted. The brushed inside feels very soft next to the skin, while still wicking any moisture away. A popular choice with our testers thanks to the soft feel, space print and thumb holes (designed to help kids get extra layers over the top without sleeves riding up) these have doubled as cosy base layers as well as warm PJs to beat the chill.

As parents, we were pleased that these versatile thermals can be machine-washed easily and are designed to withstand whatever your child can throw at them.

Long-sleeve thermals can be a little impractical for school, which is where these classic thermal vests from M&S really come into their own. Layering under polo shirts or PE tops, they are ideal for beating the chill as temperatures drop.

The soft brushed fabric got our tester’s seal of approval and washes well (we’ve seen no sign of bobbling). What’s more, there are no annoying labels around the neck.  Just the thing for adding an extra layer of warmth without adding any bulk.