Moisture Regain and Conditioned Weight: How Yarn Is Actually Sold

By YZR Sweaters · 2026-10

Every so often a buyer checks a yarn delivery against the invoice, finds the boxes a percent or two light, and assumes someone is cheating. Nine times out of ten nobody is: the yarn was weighed and priced under conditioned-weight rules that date back a century, and the weather changed in between. Understanding those rules is a small piece of textile literacy that saves awkward conversations — and occasionally real money.

What moisture regain actually measures

Moisture regain is the weight of water a fibre holds, expressed as a percentage of its dry (oven-dry) weight. Wool in a normal room holds about 16% of its dry weight as water — which means a sweater that is 13.8% water by total weight is simply "normal wool in a normal room", not a defect. Official commercial regain values, used for invoicing and for aligning yarn count systems to a standard condition, look like this:

• Wool (worsted and woollen): 16.0%
• Cotton: 8.5%
• Viscose: 11.0%
• Silk: 11.0%
• Nylon: 4.5%
• Acrylic: 2.0%
• Polyester: 0.4%

Two practical consequences follow. First, hygroscopic fibres like wool are heavier on humid days — the same cones weighed in Dongguan in August and in your warehouse in a dry winter can differ by several percent, both honestly. Second, synthetics barely hold water, which is why a 100% polyester knit invoice tracks the scale almost perfectly while a wool one does not.

How conditioned weight is calculated

The transaction works like this. The spinner (or the trading house) weighs the yarn, dries a sample to establish its actual moisture, then converts the net weight to conditioned weight using the official regain for the fibre. The invoice charges you for that conditioned weight. The formula in words: take the oven-dry weight, add the commercial regain percentage, and that is what you pay for.

Worked example: suppose a wool consignment has an oven-dry weight of 1,000 kg. Conditioned weight at 16% regain is 1,160 kg, and the invoice prices 1,160 kg. If the yarn happened to arrive damp, at an actual regain of 20%, the raw scale weight would read 1,200 kg — but you are still charged on 1,160 kg. Conditioned weight protects the buyer here; when the yarn arrives bone-dry in winter, the same rule protects the spinner. It is a symmetrical, old-fashioned, genuinely fair system — which is why it survives.

One wrinkle for blends: each component's regain is applied to that component's share of the weight, using the fibre percentages on the composition specification. A 70/30 wool/nylon blend is invoiced at a blended regain of roughly 12.35% — worth knowing when you check paperwork.

Where buyers actually get caught

• Comparing quotes on different weight bases. One supplier quotes per kg conditioned, another per kg gross delivered. On wool, that gap is 10%+ before you have negotiated anything. Always ask which basis a yarn price uses — this matters more on wool than on cotton, and far more than on synthetics.
• Reconciling with garment yield. If you calculate yarn consumption per sweater using raw delivery weights but the factory consumes from conditioned stock, your BOM drifts. Pick one basis and keep it consistent, the way disciplined factories do when building a bill of materials.
• Moisture arguments at inspection. Garment weight spec disputes often trace back to conditioning: a sweater weighed straight out of a humid finishing room is heavier than the same sweater after a day in dry air. Good inspectors weigh in a conditioned environment or note the ambient conditions, which is standard practice in lab testing.
• Storage swings. Wool can pick up or lose a few percent in storage, which is one more reason to care about how stock yarn is kept — see our notes in yarn stock planning.

We see the quote-comparison trap most often with smaller brands comparing two "wool 2/30" prices side by side. The conditioned-weight basis, the count system, and the ply and twist can each move the real price by double digits. The per-kilogram number alone tells you almost nothing.

Why this also explains sweater behaviour

Moisture regain is not just invoicing trivia — it is why wool feels the way it does. That bound water is part of wool's buffering behaviour, its comfort in changing weather, and even some of its prickle-reducing softness at higher humidity. It is also why wool garments relax after wear and recover after resting: the fibre is plasticised slightly by its own absorbed water. When buyers ask us why a wool knit "settles" differently from an acrylic one of identical GSM, moisture behaviour is a fair part of the answer.

And when wool prices swing — as they do, for the reasons we cover in our yarn price volatility guide — remember that a meaningful chunk of any wool price per conditioned kilogram is, quite literally, water. You are paying for 16% of it by agreement. Everyone in the chain knows this; now you do too.

At YZR Sweaters we quote yarn on a stated, consistent weight basis with the fibre composition and count declared, so your costings and ours reconcile to the same numbers. If you want, we will walk you through the conditioned-weight math on your own programme — it takes ten minutes and prevents a year of spreadsheet drift.

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