Merino and lambswool get used as if they were interchangeable labels for “good wool”. They are not the same thing, and the difference is not marketing — it changes how the sweater feels, how warm it is, and how long it lasts. If you are choosing between a merino wool and a lambswool sweater, here is what actually separates them.
What the two words actually mean
They describe different things, which is the root of the confusion.
Merino is a breed of sheep. Merino wool can come from a sheep of any age, and its defining property is fibre diameter: typically 17–24 microns, against 25–30 for standard wool. Thinner fibre means it bends more easily against the skin, which is why merino is not itchy.
Lambswool is an age, not a breed. It is the first shearing from a sheep under about seven months old, usually around 15–17 microns at the tip but with more variation along the fibre. Because it has never been cut before, the ends are naturally tapered rather than blunt.
So a sweater can be both. Merino lambswool exists, and it is the softest of the three options. A label reading only “lambswool” tells you the age of the animal but not the breed, and therefore not reliably the fineness.
Which is warmer, merino wool or lambswool?
Lambswool, at the same weight. This is the answer most people get backwards.
Lambswool fibres have more natural crimp — more waviness per centimetre — and crimp traps air. Trapped air is insulation. A 300g lambswool sweater will generally be warmer than a 300g merino one for that reason alone.
Merino wins on a different measure: warmth for its thinness. Because the fibre is finer, merino can be knitted to a genuinely light gauge and still insulate, which is why it is the fibre of choice for anything that has to go under something else. A fine-gauge merino-type crewneck such as The Alpine Crewneck is built on this logic — thin enough to layer, warm enough to stand alone indoors.
The practical rule: if the sweater is the outer layer, lambswool gives you more warmth. If something goes over it, merino-weight knitwear gives you more usable warmth without bulk.
Is lambswool better than merino wool?
Neither is better. They fail in opposite directions, and which failure you mind decides the answer.
Lambswool is warmer, has more loft, and holds a fuller shape — a cable or a jacquard shows better in lambswool because the stitch stands up. It also pills more in the first few weeks, because those short lamb fibres work their way loose. That early pilling settles down once the loose fibres are gone.
Merino is smoother, drapes flatter, and resists odour better, so you can wear it more times between washes. It is more prone to abrasion at the elbow and cuff over years of wear, precisely because the fibre is fine.
If you want one sweater that will be worn alone on cold days, choose lambswool. If you want one that will spend most of its life under a jacket, choose the finer fibre. The layering side of that decision is covered in how to layer a jacket over a sweater.
What is the disadvantage of merino wool?
Three, honestly.
It is weaker per fibre. Fine merino has less tensile strength than a coarser wool, so a merino knit will wear thin at high-friction points — elbows, the edge of a cuff, wherever a bag strap sits — before a lambswool one does.
It costs more. Finer fibre means lower yield per animal and more careful processing, and that reaches the price tag.
It can feel thin when you want substance. A merino knit drapes rather than holds, so if you like a sweater that keeps its own shape and gives a shoulder some presence, merino at light weight will disappoint you. A textured construction compensates — The Crewneck Knit uses a jacquard to build surface and body into a knit that would otherwise sit flat.
Is 100% lambswool good quality?
Usually yes, but the percentage is not the whole story. Two things matter more than the fibre label.
Gauge and weight. Look for the garment weight if it is listed, or judge by hand: hold the knit up to a window. If you can see clearly through it in a supposedly warm sweater, it has been knitted loosely to save yarn.
Finishing. Check where the sleeve joins the body and whether the ribbing at the cuff springs back when you stretch it. Ribbing that stays stretched will not recover after a winter, whatever the fibre is.
Blends are not automatically worse. A small percentage of nylon at the cuff and elbow measurably extends the life of a fine knit, and acrylic content keeps a sweater affordable and stable in the wash, which is the right trade for some pieces — The Noelle Pullover is built for exactly that, travelling folded and arriving without creases.
How to tell which one you are holding
Without a label, three checks get you close.
Press the knit against the inside of your wrist for ten seconds. Fine merino registers as smooth; anything you notice as prickle is a coarser fibre.
Look at the surface in raking light. Lambswool has a faint halo of short fibres standing off the surface. Merino looks cleaner and flatter.
Squeeze a handful and let go. Lambswool springs back with loft. Merino recovers but stays closer to flat.
The full knitwear range is in Men’s Sweaters and the seasonal edit in Autumn ’26. Fabric and care questions we get repeatedly are answered on Style Answers.