A one-kilogram spool of filament is not one kilogram of filament. It is a plastic spool weighing 180–260 grams, wrapped in a cardboard box, holding a nominal mass that the factory measures on its own scale, before the material absorbs moisture in a humid warehouse, before the last two metres are unusable because they are tangled, and before a print fails at hour fourteen and the whole build goes in the bin. Every one of those losses is absorbed by the distributor, not the factory, and none of them appear on the invoice. This guide is about measuring what you actually sell, because in this category the consumables line is where the margin lives and where it quietly leaks.
The stakes are larger than they look. Filament and resin typically carry 35–55% gross margin against 12–22% on capital equipment, so a distributor doing $2 million in revenue with a 60/40 equipment-to-consumables split earns more gross profit on the smaller line. A 6% unmeasured loss of usable mass on that consumables line is a direct subtraction from the highest-margin category in the business. Our filament quality evaluation guide covers incoming inspection of diameter and ovality. This article covers the mass, the moisture, the residue and the scrap — the four places the kilo disappears.
Consumables Are the Margin, and the Margin Is Unverified
Capital equipment is a commodity with a public price. Anyone can look up the street price of a printer, and the distributor's margin is set by what the market will bear against a known cost. Consumables are different: the buyer compares price per kilo, not price per usable gram, and the true yield of a spool is invisible at the point of purchase.
That asymmetry is what makes the category profitable and what makes it fragile. A supplier who ships 950 grams on a nominal 1,000 gram spool gains 5% on every unit, and the distributor absorbs it as a slightly worse margin that nobody can quite explain. Multiply across a container of 5,000 spools and the loss is 250 kilograms — a quarter tonne of filament paid for and never sold.
The variance between the low and high end of those loss ranges is entirely a function of whether anyone is measuring. A distributor who weighs one spool per batch and samples one bottle per container knows; one who does not has a margin that drifts and a supplier relationship negotiated on faith.
Net Weight Verification: Tare, Gross and the Spool Itself
The measurement starts with a fact almost nobody writes into a purchase order: the spool is part of the product. Empty spools range from 140 grams for a thin plastic reel to 300 grams for a heavy cardboard or reinforced core, and the difference between a supplier using a light spool and one using a heavy spool can exceed 100 grams per unit without any change in the filament inside.
To verify, weigh a spool gross, then weigh an identical empty spool from the same supplier and subtract. Do not use a nominal tare from a datasheet. The scale needs 1 gram resolution with a 2 kilogram capacity, which costs $40–90. A 5 gram resolution kitchen scale is useless here because the tolerance band you are testing is often only 10–20 grams.
The sampling procedure matters as much as the scale. Weighing the top spool in a carton tells you nothing about the carton. Use an acceptance sampling plan: for a container of 1,000–5,000 spools, sample 13 units for a general inspection level and accept the batch if no more than one unit falls below the declared tolerance. If two units fail, escalate to 32 units. Our filament quality evaluation guide covers the companion diameter and ovality checks that run on the same samples.
Write the tolerance into the supply agreement explicitly: net weight 1,000 g minus 2%, tare excluded, measured on a calibrated scale, batch accepted or rejected on an AQL 2.5 plan. A supplier who will not sign a net-weight clause is telling you something about the spool.
Moisture: The Hidden Kilo
Filament absorbs water from the air, and the absorption is not a surface effect. Nylon can take up 1.5–3.0% of its mass in moisture within days of exposure to humid air; PETG and TPU take up 0.3–1.0%; PLA is comparatively stable at 0.1–0.3%. A nylon spool that leaves the factory dry at 1,000 grams and reaches your warehouse at 1,020 grams has not gained product — it has gained a printing defect.
The commercial consequence runs both ways. Moisture pick-up makes a spool heavier, so if you verify net weight against a nominal figure without drying first, wet spools pass the weight check while being functionally defective. Conversely, if you dry a spool before weighing it, a short-filled spool reveals itself — which is exactly why some suppliers resist dry-weight specifications.
Measure moisture rather than infer it from mass. Two instruments cover the need: a pin or capacitance moisture meter built for filament ($30–120) which gives a rough indication in seconds, and a loss-on-drying test using a 70 °C oven and the same 1 gram scale, which gives a real number. Dry a 50 gram sample for 8 hours at 70 °C, reweigh, and the mass difference divided by the dry mass is your moisture content. On a 1,000 gram spool, 1% is 10 grams of water that will boil inside the hotend and produce the surface defects your customer will blame on the printer. Our nylon PA filament guide covers the storage and handling regime for the worst offender.
Resin Fill Level: Bottles, Cartridges and the Missing Millilitres
Resin has its own version of the missing kilo, and it is easier to hide because the container is opaque. A nominal 1 litre bottle holds whatever the bottling line dispensed, and the line does not care much about a 20 millilitre shortfall.
Three losses occur. Fill level — bottle fill variance of 1–3% is common in the category and outside a supplier's stated tolerance is a legitimate claim. Residue — 3–8% of the contents remain in the bottle or cartridge and never reach the vat, because the resin is viscous and the bottle shoulder traps material. Headspace and evaporation — volatile components leave an opened bottle, changing both mass and print behaviour.
Verify by weight, not by eye. Resin density runs 1.05–1.15 grams per millilitre depending on formulation, so a nominal 1 litre bottle should weigh 1,050–1,150 grams gross minus the container tare of 60–120 grams. Weigh three bottles per carton, compare against the declared density on the technical datasheet, and you have a defensible fill-level measurement without opening anything.
The residue problem is the one to price, not to eliminate. A cartridge system that pushes resin out mechanically leaves less behind than a gravity-drained bottle, and that difference of 4–5% is worth paying a small premium for on high-volume accounts. Compute it explicitly: at $60 per litre and 5 litres used per week, 5% residue is $15 a week, $780 a year, per printer. Our resin margin comparison guide covers the category-level margin arithmetic that this sits inside.
True Cost per Kilo: Landed, Dried, Printed
Invoice price per kilo is the number distributors quote to each other and it is the wrong number. The number that determines whether the category is profitable is the cost of a kilogram that is actually extruded into a customer's part.
The formula has four terms and each is measurable.
Term 1 — landed cost. Invoice value plus freight plus duty plus customs clearance, divided by net received mass. A $18/kg invoice with $2.40/kg freight and 6.5% duty on a 950 gram net spool lands at approximately $23.30 per kg of material you can theoretically sell.
Term 2 — drying cost. The energy and handling to bring the spool to a printable moisture level, plus the mass lost in drying. A 12-hour dry at 300 W is 3.6 kWh, and at $0.20/kWh that is $0.72 per spool before labour. Handling is the larger cost: 4 minutes of labour at $22/hour is $1.47.
Term 3 — unusable remainder. The last 20–60 grams on a spool that cannot be reliably fed, plus tangles and splice failures. Budget 1.5–3% of net mass on a well-wound spool and 4–6% on a poorly wound one.
Term 4 — scrap from failed prints. Average print failure rate in a well-run farm is 3–7%, and each failure consumes material that produced no revenue. This is the largest single term and the least often counted.
A 44% gap between invoice and true cost is the reason a distributor can be pricing at what looks like a 40% gross margin and be earning 18%. The same arithmetic applies to the customer's side of the invoice, which is why the distributors who explain it win the account: the buyer comparing $18 and $22 per kilo is comparing the wrong figures, and the distributor who shows them the landed-and-dried comparison sells the $22 spool. Our distributor pricing strategy guide covers how to build that into a price book.
Failure Scrap: The Multiplier Most Models Ignore
The scrap term deserves its own treatment because it is the largest and most variable. A failure at hour fourteen of a twenty-hour print wastes the material already extruded plus the bed, the nozzle wear and the machine hours, and the customer sees all of it as your product's fault even when the root cause is a moisture problem they created.
Typical failure rates by material and context: PLA on a well-tuned machine 2–4%, PETG 3–6%, ABS/ASA 5–9% on an unenclosed machine and 3–5% enclosed, nylon 6–12% when moisture is not controlled and 3–6% when it is, resin 4–10% depending on supports and exposure calibration. Your own incoming inspection changes these numbers more than any other single variable, because a spool that is over-diameter or oval will fail at a predictable rate regardless of what the operator does.
Track failure rate per batch, not per material. A supplier whose batch fails at 9% while every other supplier's sits at 4% is costing you 5% of that batch's material plus the machine hours, and that is a claim you can only make if you have been recording. The claim conversation is much easier when it is a documented trend line rather than a complaint. Our purge waste economics guide covers the related losses on multi-material systems where every material change discards additional filament.
Building a Verification Lab Without a Lab
The entire measurement programme fits on a bench and costs less than one container's worth of dispute.
The procedure is four steps per receiving batch. Weigh three spools gross and record. Weight-dry a 50 gram sample from one spool to establish moisture content. Weigh three bottles of resin where applicable and compare to declared density. Log the print failure rate for the batch over its first two weeks of sale, from customer reports and warranty claims.
Store the data in one table with the supplier name, batch number, receipt date and the four measurements. After four batches you will have enough to rank suppliers. After eight, you will have enough to renegotiate terms — and a supplier whose net weight or moisture is consistently at the wrong end of the band will either fix it or leave, and both outcomes are improvements. Our bed adhesion consumables guide covers the adjacent category where adhesion failures are usually misdiagnosed as material faults.
Supplier Conversations: Claim Thresholds, Sampling Clauses and Credits
Verification without contractual teeth produces data and no money. The supply agreement needs four clauses, and they are all short.
Net weight specification. Declared net mass, tolerance of minus 2%, tare excluded, measurement method named. Acceptance on an AQL 2.5 sampling plan at general inspection level, with the sample size stated. Rejection remedies: replacement, credit or price adjustment at the buyer's option.
Moisture specification at shipment. Maximum moisture content at the time of dispatch, with the test method. This is the clause that prevents wet spools from passing a weight check, and it is the one most often missing.
Batch traceability. A batch or lot code on every spool and every carton, recorded on the packing list. Without it, a failure trend cannot be attributed and no claim survives the conversation.
Claim window and credit process. A stated period — 30 to 60 days from receipt is normal for consumables — within which claims are accepted, the evidence required, and the remedy. A supplier who offers replacement credit rather than cash refund is usually the better outcome, provided the replacement is from a different batch.
Negotiate these before the first container, not after the first bad one. A supplier who will not accept a net-weight clause or a lot code is a supplier whose margin is coming from somewhere you cannot see. Our OEM pricing negotiation guide covers the broader commercial conversation these clauses sit inside.
Bottom Line
Four measurements, one table. Weigh the spool, dry the sample, weigh the bottle, track the failure rate. Those four data points convert consumables from the category where margin quietly disappears into the category where you know your true cost to the cent and can prove it to a supplier.
The commercial payoff is double: you stop absorbing a 3–8% mass loss you never priced, and you gain the evidence to sell on true cost per usable kilo rather than invoice price — which is a conversation a distributor wins, because most competitors cannot have it. Our pellet extrusion cost per kilo guide covers the alternative raw-material route for distributors serving high-volume customers.
Reviewed by the Precise3D engineering & OEM team. Compliance files that accompany the catalog are auditable at the certification register.
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Batch lot codes, net-weight tolerances and moisture specifications are available on every consumables line. Ask for the specification sheet before your next order.