How many decimals should I print on variable-weight labels?

Print the decimals required by market/standard and supported by device capability. Perform calculations at higher precision and format for print to avoid double rounding.

Can I claim volume but control by weight?

Yes, but density and temperature correction become governed master data and part of measurement uncertainty. Version, verify, and include in executed net and label rules.

Do I catch weight at unit or case level?

Unit nets are preferred for legal claims and pricing; cases should roll up unit nets. Case-only weighing requires evidence that case math equals the sum of components and regulatory acceptance.

Catch WeighingGlossary

Catch Weighing – Variable‑Weight Item Control

Q: Is catch weighing still needed if I use an in-motion checkweigher?

Yes. Checkweighers screen for out-of-tolerance units; catch weighing creates the legal and accounting record per unit and prints the compliant label.

Q: What if the line scale and lab balance disagree?

Pause release, verify calibration status, perform side-by-side checks, reconcile bias, and document under Deviation/CAPA before resuming.

Q: Where do most under-fill violations come from?

Poor tare control, decimal truncation, and unresolved device bias. Fix tare governance, increase internal precision, reconcile devices, and stabilize with SPC.

This topic is part of the SG Systems Global regulatory & operations glossary.

Updated October 2025 • Weigh‑Price Labeling, Net Content, GS1/EPCIS, Part 11 • Packaging, QA, Manufacturing, Supply Chain

Catch weighing is the disciplined capture of actual net weight for items whose mass varies unit‑to‑unit. Instead of assuming a fixed nominal, each pack, tray, bottle, or bag is weighed at the moment of make/pack, its net computed (gross minus controlled tare), and the result drives labeling, release evidence, inventory, costing, and—in many sectors—price. This is routine in food (meat, cheese, produce) but equally relevant to regulated manufacturing where fill variability is real (creams, gels, semi‑solids, coated parts). The blunt truth: if you sell, release, or account for variable‑weight items without rigorous catch weighing, you’re flying blind—exposed on compliance, margin, and customer trust.

“If you don’t weigh it, you guessed it. Guessing is not a control strategy.”

TL;DR: Catch weighing turns random unit variation into governed data. Weigh at point‑of‑pack using qualified devices (gravimetric weighing), subtract controlled tare, print compliant labels with GS1 GTIN and weight AIs, and stream results into MES/WMS for genealogy, release, and Pack & Ship. Protect it with Part 11/Annex 11, audit trails, and MSA. Use SPC to shrink over‑give and TNE risk. No offline edits. No shared logins. No “print first, weigh later.”

1) What Catch Weighing Covers—and What It Does Not

Covers: weighing individual saleable units (and/or cases) whose content varies; computing net using governed tare; encoding the weight on the label and in the electronic record; posting the net to inventory and order lines; and consuming the weight in pricing, compliance, and shipping. Catch weighing also covers case/pallet aggregation where case net equals the sum of unit nets, plus packaging tare. It includes device integration (bench scales, weigh‑price labelers, in‑motion checkers), label verification, and posting to EPCIS events for downstream traceability.

Does not cover: pretending “nominal” equals truth, averaging away under‑fills, or treating tare like folklore. Catch weighing isn’t an excuse to skip capability work. Nor is it a bypass for net content law; if you print an actual weight, that printed weight becomes the legal claim—miss it and you’re out of compliance. Finally, catch weighing doesn’t replace weigh/dispense for GxP materials; it complements it at pack.

2) Legal, System, and Data Integrity Anchors

Variable‑weight labeling is anchored in weights‑and‑measures and product‑specific rules (e.g., U.S. food labeling under 21 CFR Part 101 and preventive controls under Part 117). When the weight record supports release or disposition, electronic evidence must also satisfy Part 11/Annex 11: validated software (CSV), unique users, time‑stamped audit trails, and durable retention. Measurement devices demand IQ/OQ/PQ, active calibration status, and competence per ISO/IEC 17025. Tare values, density factors (when claiming volume), and rounding rules belong under Document Control. If any link is weak—device out of status, users shared, time unsynchronized—your label claims are vulnerable.

3) The Evidence Pack for Catch‑Weight Compliance

A defensible catch‑weight setup comes with receipts. Build a pack that shows: the instrument list with IDs and status; V&V for weighing workflows and label outputs; tare libraries with version/lot controls; UOM conversion and rounding policies; GS1 label templates (GTIN, lot, serial, net weight AIs); print and reprint logs; label verification results; genealogy showing unit/net bound to batch; and internal audit checks of time sync and backup/restore. If asked, you should be able to reconstruct the printed number from raw signals and master data in minutes—not days.

4) From Goods Receipt to Label Claim—A Standard Path

1) Goods Receipt. Components and packs arrive via Goods Receipt; tare‑bearing items (trays, films, vials) are lot‑captured with target tare and variability data. Stock is put away per FIFO/FEFO rules in the WMS.

2) Line Setup & Clearance. Scales are verified in status; warm‑up and zero tracking are confirmed; line clearance prevents mixed lots; current label artwork and GS1 template versions are loaded under Document Control.

3) Execute & Weigh. Each unit is weighed; gross is captured; the system applies the correct tare and conversion (and density if claiming volume by mass) to compute net; ranges and rules are enforced.

4) Print & Verify. A compliant label is printed with GTIN, lot, net weight AIs, dates, and (if used) serials; scanners perform label verification. No label = no move.

5) Post & Aggregate. Net weight posts to the MES/eBMR, inventory, and order lines; cases sum unit nets; pallets get an SSCC. ASN includes weight fields.

6) Release & Ship. QA reviews records; Release Status transitions to shippable; Pack & Ship hands off to carriers with accurate declared weights. If prerequisites fail at any step, execution blocks and a guided Deviation/CAPA path opens.

5) Weighing Physics—Minimum Weight, Drift, and Vibration

Scales obey physics, not wishful thinking. Respect minimum weight (below which relative error explodes), warm‑up times, zero tracking behavior, and vibration/airflow sensitivity. Locate scales away from fans and conveyors that induce noise; establish daily zero/span checks and periodic challenge weights under MSA. For in‑motion checkers, validate dynamic error against a reference balance and quantify compression/averaging behaviors. Put numbers on drift; if drift accumulates faster than your review cadence, your process is out of control even if the screen looks stable.

6) Tare Strategy—Static, Dynamic, and By Lot

Tare is not a constant—it’s a distribution. Manage it like one. Store target tare and σ by packaging lot; verify empties before release; re‑verify when lots change or environmental conditions shift. For moisture‑sensitive packs, consider dynamic tare capture (periodic empty pack weighs on the line) to track drift. Treat films, lids, and inserts as real contributors; their variability can swing a label claim. Govern changes through Document Control and link tare versions to label logic and MES recipes so the right value is applied without operator math.

7) UOM & Conversion Logic—Decimals Decide Outcomes

Catches fail quietly on units. Fix the math: declare primary UOM (EA) and secondary (kg/lb) for inventory; set precision by SKU and by label market; avoid double rounding by doing all math at full precision then formatting for print. If you claim volume but control by mass, treat density as a governed parameter with temperature correction and versioning. Consolidate conversion tables under UOM conversion, not tribal spreadsheets. When regions demand different decimal policies, version label templates and conversion rules under Change Control.

8) Net Content Law, Average System & TNE

If your label prints an actual weight, that number is the legal net for that unit; precision and accuracy must be defensible. In average‑system jurisdictions, the batch still faces tests on the distribution—e.g., limits on how many can be below the declared amount and the Tolerable Negative Error (TNE) for any one unit. Guardband intelligently: center your process so observed nets rarely challenge TNE while avoiding chronic over‑give that burns margin. Use SPC (X‑bar/R, individuals) with alert/action limits and track Cp/Cpk. If you’re underweight at the lab but “fine” on the line, your devices disagree—stop and reconcile before you ship risk.

9) Labels & Barcodes—Encode the Truth, Not a Story

Encode weight so customers and systems can trust it. Use GS1 AIs: (01) for GTIN, (10) for lot/batch, (15) for best‑before, (21) for serial (if used), (310x) for net weight in kg with x decimals, or (320x) for net weight in lb. Aggregate units into cases with an SSCC (00) and transmit weights on the ASN. Validate print quality and content with label verification (machine or vision). Reprints must carry reason codes and link back to the original record in the audit trail; uncontrolled reprints are a counterfeit factory.

10) Pricing, Costing & ERP—Weight Is Money

When price follows weight (produce, proteins, chemicals), catch weight is revenue logic, not just compliance. If you sell by each but cost by weight, you still need catch weight for margin transparency. Ensure ERP supports dual UOMs and price extension by captured net; post differences between expected and actual as usage/yield variances. Don’t let carriers charge you for dead air—ship weight should match caught weight at case/pallet. If your freight audit finds a 5% systematic delta, look at pallet tare and case aggregation math first.

11) MES/WMS Integration—No Manual Keying

Wire devices to systems so people don’t retype numbers. The MES should capture gross from the scale, apply governed tare/UOM/density, and publish net to the WMS with unit ID, lot, and label ID. For weigh‑price labelers, integrate bi‑directionally: master data and templates down, results and reprints up. Validate mappings end‑to‑end; silent truncation of decimals is an expensive bug. No offline edits, no “late entry,” no spreadsheet bridges—ever.

12) SPC & Capability—Shrink Over‑Give Without Risk

Chart live nets. Use individuals charts for unit data and X‑bar/R for subgroups where appropriate. Pair charts with UCL/LCL and rules for trends/runs. Quantify Cpk against TNE boundaries to estimate under‑fill risk, and calculate over‑give cost ((mean − nominal) × volume). Tackle the cheapest lever first: stabilize fill temp/viscosity, tune nozzles, improve tare governance. The goal is a small guardband with low σ, not heroically high targets that leak cash forever.

13) Sampling & Cross‑Checks—Trust but Verify

Even with 100% catch weighing, run cross‑checks. At defined intervals, weigh representative units on a calibrated reference balance; investigate if bias vs. the line exceeds tolerance. Use sampling plans appropriate to risk. Treat “line happy, lab sad” as a signal: halt release, check calibration, repeat comparisons, and document under Deviation if bias persists. For high‑risk SKUs, increase frequency temporarily until the system proves stable again.

14) Case & Pallet Catch Weight—Aggregation That Adds Up

Case math must be deterministic. Sum child unit nets to get case net; add case tare; print case label (with SSCC) and post to inventory. For mixed‑weight cases, enforce expected weight bands and flag outliers for inspection. Pallet weights can validate case totals and catch “air pallets” (missing case) or double counts. Include aggregations on the ASN so customers reconcile upon receipt. If customers keep finding 2–3% deltas, it’s not freight—it’s your aggregation logic or label duplication.

15) Cold Chain & Moisture—Weight That Moves Overnight

Some products lose or gain mass post‑pack (evaporation, purge, water activity). Quantify it. Use Hold Time Studies to model loss and set process targets that still protect TNE at the time consumers weigh. Store/ship conditions matter: integrate environmental data (Temperature Mapping, EM) with lot history. If moisture loss blows your label claim, either tighten the process or change the claim. Wishing doesn’t add grams back.

16) Cybersecurity & Data Integrity—No Ghost Weights

Apply named accounts (UAM), role‑based permissions, and time synchronization. Protect device configurations under Change Control. Record every critical action in the audit trail and review routinely. Back up historians and label servers; test restores. If “lost labels” or “lost weights” occur, assume integrity breach until proven otherwise and document the path to remediation. Ghost data equals regulatory debt.

17) Common Pitfalls & How to Avoid Them

Printing before weighing. Guarantees mislabels and rework—reverse the flow or block labels until a valid weight exists.
Uncontrolled tare. Treat tare like a fixed constant and you’ll drift into non‑compliance. Manage tare by lot and verify.
Decimal/rounding errors. Double rounding changes legal claims. Do math in high precision; format at print.
Shared logins. Destroys attribution. Enforce named accounts with session locks.
Reprint loopholes. Reprint without trace = counterfeit. Force reasons and link to the original record.
Device disagreements. Line vs. lab bias left unresolved leads to recalls. Reconcile, then release.
Offline edits & spreadsheets. Manual keying corrupts evidence. Integrate or don’t ship.
Aggregation mistakes. Case/pallet math must add up, every time. Automate sums and spot‑check with pallet scales.
Ignoring environment. Temperature and humidity move grams. Control or compensate.
Slow feedback. If SPC signals take hours to reach operators, you are paying to over‑give.

18) Metrics That Prove Control

Sub‑TNE Risk (% below legal threshold) and over‑give cost per SKU/line.
Label Reprint Rate and % with documented reasons.
Scale Status Compliance (in‑status time, missed checks).
SPC Stability (rule breaks per 10k units; time to correction).
Aggregation Accuracy (case/pallet delta vs. sum of units).
ASN Weight Accuracy (customer‑reported deltas).
Audit‑Trail Review Health (overdue significant events = zero).

Dashboards must trigger action, not decorate meetings. If a metric doesn’t change behavior, delete it.

19) What Belongs in the Catch‑Weight Dossier

Include the scope of variable‑weight SKUs; device inventory and status; V&V evidence; tare/density master data with versions; UOM/rounding policy; GS1 label templates; print/reprint logs; label verification results; SPC charts and capability; cross‑check studies; aggregation (case/pallet) logic; EPCIS event examples; backup/restore logs; and the last three internal audits with closures. House it under Document Control.

20) How This Fits with V5 by SG Systems Global

Device‑Tight Execution. The V5 platform captures gross directly from qualified scales, applies the current tare/density/UOM rules, and writes net to the eBMR and inventory in real time. No manual keying, no clipboard math.

Labels That Match Evidence. V5’s label engine consumes the executed net and prints GS1 with weight AIs; Label Verification ensures the barcode matches the record. Reprints are e‑signed and audit‑trailed.

Aggregation & ASN. Cases sum unit nets; pallets roll up cases and print SSCC; ASNs include accurate declared weights.

SPC, CPV & Savings. Live SPC and CPV watch distributions and quantify over‑give. Drill‑downs reveal which lines, shifts, or tare lots drive cost, so you fix the cheapest root cause first.

Bottom line: V5 makes catch weighing automatic, auditable, and profitable—what you weigh is what you print, ship, and invoice.

21) FAQ

Q1. Is catch weighing still needed if I use an in‑motion checkweigher?
Yes. Checkweighers screen; catch weighing creates the record of truth. Use checkweigher data for SPC and rejection; use catch‑weight stations to compute, print, and post legal net per unit.

Q2. How many decimals should I print?
Print what your market requires and your device can defend. Do calculations with higher internal precision and only format for the label. Govern this under UOM conversion and Document Control.

Q3. What if the line scale and lab balance disagree?
Treat it as a data‑integrity signal. Pause release, check calibration status, re‑weigh a sample set, and reconcile. Document under Deviation/CAPA before resuming.

Q4. Can I claim volume but weigh mass?
Yes, but density/temperature corrections become part of measurement uncertainty. Version and verify them and include in the executed net and label rules; see Gravimetric Weighing and UOM conversion.

Q5. Do I catch weight at unit or case?
Unit nets are safest for legal claims and pricing; case nets can be derived as sums. If you only weigh cases, ensure evidence proves case math equals the sum of components and that labeling laws accept case‑level claims for your product.

Q6. Where do most under‑fill violations come from?
Sloppy tare, decimal truncation, and device disagreement. Fix tare governance, raise internal precision, reconcile devices, and stabilize the process with SPC.