Yield

Similar to tex and denier, yield is a term that helps describe the linear density of a roving of fibers. However, unlike tex and denier, yield is the inverse of linear density and is usually expressed in yards/lb.

A roving is a long and narrow bundle of fiber. Rovings are produced during the process of making spun yarn from wool fleece, raw cotton, or other fibers. Their main use is as fibre prepared for spinning.

Linear density is the measure of a quantity of any characteristic value per unit of length. Linear mass density (titer in textile engineering, the amount of mass per unit length).

The SI unit (International System of Units) of linear mass density is the kilogram per meter (kg/m). Linear density of fibers and yarns can be measured by many methods. The simplest one is to measure a length of material and weigh it. However, this requires a large sample and masks the variability of linear density along the thread, and is difficult to apply if the fibers are crimped or otherwise cannot lay flat relaxed. If the density of the material is known, the fibers are measured individually and have a simple shape, a more accurate method is direct imaging of the fiber with SEM to measure the diameter and calculation of the linear density. Finally, linear density is directly measured with a vibroscope. The sample is tensioned between two hard points, mechanical vibration is induced and the fundamental frequency is measured.

Learn about fabric utilization which is also referenced at times as the yield of fabric.

Why Buyers Think in Yield

Mills buy fiber by weight and sell what it becomes by length and area, so yield is the number that connects the invoice to the output. A spinner planning an order works backwards from the yards of yarn required to the pounds of roving that must be purchased, and a small shift in yield — from fiber variation, moisture or waste — moves the true cost of the order. That is why yield is checked rather than assumed: a measured length of roving is weighed under controlled conditions, and the result is compared with the nominal yield the material was bought at, with differences settled between buyer and seller.

The Inverse Relationship, Made Concrete

Because yield and tex describe the same property from opposite ends, their product is a constant: double the tex and the yield halves, as the table on this page shows — 1100 tex yields about 450 yards per pound, exactly half the 900 yards of a 550 tex roving. Fluency in both directions matters because different trades settled on different sides of the relationship: fiber and roving merchants often quote yield, yarn engineers usually work in tex or denier, and the definitions linked from this page — denier among them — fill in the remaining conversions a working spec may demand.