What Is the Lowest Micron Merino? Ultrafine and Extreme Ultrafine Explained
Sullivans International
•3 min read
Merino wool is graded by micron—the diameter of the fibre in micrometres (µm). The lower the micron, the finer and softer the wool. Merino at 18 µm or less is classed as ultrafine; the lowest micron Merino can be around 11 µm, often called extreme ultrafine. Ultrafine and extreme ultrafine are very soft and silky but more expensive and more delicate; higher micron Merino (e.g. above 20 µm) is coarser, more durable, and more practical for everyday or heavy use.
This guide explains what the lowest micron Merino is, how micron affects quality, and how to choose by use and budget.
Micron (µm) is the average diameter of the wool fibre. It directly affects softness, itch, and performance: lower micron = finer, softer; higher micron = coarser, stronger. Merino is one of the finest sheep wools, so it is often labelled by micron for quality and price.
The lowest micron Merino is around 11 µm, marketed as extreme ultrafine Merino. In practice:
So the lowest you will see is in the ~11 µm range (extreme ultrafine); 18 µm or less is the standard ultrafine band.
| Micron range | Classification | Typical use |
|---|---|---|
| ~11 µm | Extreme ultrafine | Luxury base layers, high-end knitwear |
| �8 µm | Ultrafine | Soft garments, activewear, next-to-skin |
| ~19�0 µm | Fine | Everyday sweaters, versatile |
| >20 µm | Medium / coarser | Heavier sweaters, blankets, durable wear |
Brands may use different grading or labels; check product descriptions and reviews for actual micron or “ultrafine�claims.
The lowest micron Merino is around 11 µm (extreme ultrafine); 18 µm or less is ultrafine�very soft* and premium. Lower micron means softer and more luxurious but pricier and more delicate; higher micron is coarser, more durable, and better for everyday or heavy use. Choose by intended use, comfort, and budget.
Micron is the fibre diameter in micrometres. Lower = finer and softer; higher = coarser and stronger.
Yes. 18 µm is in the ultrafine range�very soft* and suitable for next-to-skin and quality garments.
Ultrafine wool comes from selected Merino sheep and smaller clip volumes; processing and quality control are higher, so price is higher than standard Merino.
This article is part of our yarn knowledge series, offering practical insights into Merino wool grades and micron for knitters and outdoor apparel.