Net content and weight control calculator
Enter the nominal quantity and your pack weights. The calculator finds T and the T1 and T2 limits, tests the three average-quantity rules, sets a legal fill target with the three-way rule, simulates an NRCS reference test, checks a checkweigher threshold and draws X-bar/R charts by filler head. Nothing is sent anywhere.
A free practice tool for QC inspectors, weight-control clerks, production team leaders and own-label technologists in South African food and beverage plants. Net content is set by the Legal Metrology Regulations (GN R877 of 24 August 2018) and SANS 458, and enforced by NRCS Legal Metrology. The tool comes loaded with case data from Isipho Beverages and Snacks, a fictional plant in Hammarsdale, KwaZulu-Natal, and six practice lots.
The rules check works well on a phone. The X-bar/R charts are best on a laptop or tablet.
How to use this calculator
- Rules check. Enter the nominal quantity (Qn), how you weighed (net or gross) and the pack weights. Subtract the tare, and convert volume products with the density at 20 °C. The tool classes every pack and tests the three rules.
- Target fill. Enter your filler’s standard deviation (σ). The tool works out the three candidate targets and flags the one that governs, then shows the give-away in grams and rand.
- NRCS reference test. Would this lot pass if an inspector sampled it today? The tool simulates the OIML R87 official reference plan many times over.
- Checkweigher. Check a reject threshold and the test packs that prove it.
- X-bar/R by head. Paste 5 weights per subgroup, one line per subgroup, for each head. The tool draws the charts and applies three run rules.
- Record. Add lots to the weight-control record, then print it or download it as a spreadsheet.
Separate weights with spaces or new lines. A decimal comma (129,7) also works.
// The course behind this tool
Keep every lot legal without giving product away
This calculator comes from Module 3 of the QC Inspector Course for Food and Beverage Manufacturing (FS60-0602): calibration and verification, scale and checkweigher checks, the SANS 458 rules, fill targets and X-bar/R charts by filler head. Other modules cover specifications and AQL sampling, line clearance, metal detection and X-ray, seals, beverage and heat-treated product checks, holds, rework and CCP records.
This tool stays free. Also free: the AQL Sampling Plan Calculator for lot audits.