Fiber Directory

Alpaca vs cashmere vs merino: which is warmest and softest?

How the three premium knitwear fibers compare on softness, warmth, itch and care, with brands and makers for each.

Published October 5, 2026

All three are animal fibers used for knitwear, base layers and accessories, and all three are far softer than ordinary sheep's wool. The differences come down to how fine the fiber is, how it holds warmth, and how it behaves against skin.

Softness comes from fineness

Wool fibers are measured in microns (thousandths of a millimeter), and finer fibers feel softer and itch less. As a rough guide, cashmere is typically around 14–19 microns, merino roughly 15–24 microns, and alpaca varies more widely by grade, from the high teens for the finest “baby” grades into the high 20s and beyond. Ordinary wool is coarser still. A fine merino and a mid-grade cashmere can feel very similar: the grade matters as much as the animal.

Warmth

Many alpaca fibers are partly hollow, which traps air and makes alpaca warm for its weight. Cashmere is prized for lightweight warmth in fine knits. Merino is the most versatile: it regulates temperature well across a wide range, which is why it dominates base layers and outdoor clothing.

Itch and sensitivity

Alpaca has no lanolin, the natural grease in sheep's wool that some people find irritating. Whatever the fiber, coarser yarns itch more, so if you have sensitive skin, a fine grade matters more than the species.

Durability and care

Finer fibers are more delicate, and cashmere pills more readily than sturdier yarns. Merino base layers are often blended with a little nylon for durability, so check the label if you want 100% natural. All three are best washed cool and dried flat.

Which to choose