Super Numbers in Wool: What Super 100s, Super 120s, and Super 150s Actually Mean

Super numbers describe the fineness of the wool fibres used in a suiting fabric — specifically, the average diameter of the individual wool fibres measured in microns. A higher super number indicates finer fibres. The system was developed as a way of communicating the quality of a wool fabric independently of its weight, construction, or country of origin.

What the Numbers Measure

The super number is derived from the yarn count — a historical measure of how many hanks of yarn of a given weight can be spun from one pound of wool. A fabric described as Super 100s is made from wool fibres fine enough to produce yarn at a count of 100 (in the British worsted count system). Super 120s is finer; Super 150s is finer still. The finest commercially available super numbers reach into the Super 200s and beyond, though at these extremes the practical advantages diminish while the fragility increases significantly.

In approximate micron terms: Super 100s wool is typically 18.5 microns or less. Super 120s is around 17 microns. Super 150s is around 15.5 microns. For comparison, a human hair is approximately 70 microns in diameter. At Super 150s and beyond, the individual wool fibres are exceptionally fine — softer to the touch and more difficult to work with in manufacturing.

What Finer Wool Means in Practice

Finer wool fibre produces fabrics with several specific qualities: a smoother surface, a finer and more lustrous drape, a softer hand, and a lighter weight at comparable fineness of weave. A Super 130s fabric in navy will have a noticeably smoother surface than a Super 100s fabric in the same colour and construction — the fibres are fine enough that they reflect light more evenly, creating the characteristic lustre of fine worsted suiting.

This smoothness and lustre is part of what makes fine suiting visually elegant. But it comes with tradeoffs. Finer fibres are more delicate: a Super 150s fabric is significantly less resistant to abrasion than a Super 100s fabric, tears more easily if caught on a sharp edge, and may begin to show wear — pilling, thinning, shining at the seat and elbow — sooner under heavy use. The very finest super numbers (Super 180s and above) produce fabrics of extraordinary beauty that are genuinely fragile.

The Practical Range for Suiting

For a suit intended for regular professional wear, the practical range is Super 100s to Super 130s. Within this range, the fabric is fine enough to produce an elegant, smooth finish with good drape, while remaining durable enough for a suit worn multiple times per week over several years. Super 100s and Super 110s are particularly recommended for heavy-use suits: they wear better, travel better, and are less susceptible to the surface damage that higher-number fabrics show under equivalent wear.

Super 130s to Super 150s is appropriate for occasional-wear suits — formal events, special occasions — where the suit will not be worn more than once or twice a month. The increase in surface refinement and softness is genuine and visible; so is the reduction in durability. Above Super 150s, suits are best understood as luxury objects rather than working garments, worn rarely and maintained carefully.

Super Numbers Are Not the Whole Story

Super numbers describe fibre fineness only. They do not describe the fabric's weight, its weave structure, the quality of the spinning and weaving, or the mill's finishing expertise — all of which significantly affect the finished fabric's quality and character. A Super 110s fabric from a premium Biella mill like Loro Piana or Vitale Barberis Canonico will typically be superior in all dimensions to a Super 150s fabric from a lesser mill, because the craft invested in spinning, weaving, and finishing adds as much to quality as the fibre fineness alone.

Related terms: twill, melton, and flannel — canvas