Bag Costing for PP Woven Sacks & Packaging

A cost sheet is the one page that shows how a bag's price was built: every raw material with its weight and rate, every process with the kilograms passing through it and its rate per kilogram, then waste, overhead, freight and margin. Its purpose is not the total at the bottom — it is that any line can be questioned. A quotation without a cost sheet behind it is a guess with a decimal point.

Five steps. One, fix the specification — size, mesh, denier or GSM, coating, film micron, print, bottom type. Two, turn the specification into the weight of each component. Three, add process waste to get the kilograms one bag consumes. Four, multiply each material by its dated rate and add the conversion cost of each process the bag actually visits. Five, add overhead and freight, then apply margin on selling price. The bag costing calculator does steps one to three for you.

Bag costing is one article. Packaging costing is the whole pack — the sack, its liner, the label, the print, and sometimes the bale and the pallet the bags ship on. The method is identical; packaging costing just has more articles and usually a customer-specific combination of them, which is why it belongs in a costed Bill of Materials rather than in a single sheet.

Apportion it per kilogram of saleable output, not per bag and not as a percentage of material. Total the overheads that are not already inside a process rate — rent, supervision, quality, general maintenance — and divide by the kilograms you actually sell in a normal month. A percentage of material cost moves the overhead every time resin moves, which is the wrong behaviour.

On selling price. Cost ÷ (1 − margin %) gives the price that leaves you the margin you intended. Adding a percentage to cost gives a smaller margin than the number suggests — add 20% to cost and you have earned 16.7% of the price, not 20%. On a high-volume, thin-margin product that difference is most of the profit.

Work it per bag, not per consignment. Bags per bale, bales per truck and the truck rate to that destination give a rupee-per-bag freight that can sit as a line in the cost sheet. Quoting ex-works and absorbing freight later is how a profitable order becomes a break-even one on a long haul.

The rate a material actually costs you once everything around the invoice is accounted for: the basic rate, less any discount, plus inward freight and handling, and with recycled or reprocessed content blended in at its own rate. Costing on the printed invoice rate alone is optimistic by exactly the amount you spend getting the material into the plant.

Do not recost the approved ones. An approved quotation must keep the rate it was costed at, or you lose the ability to explain a price to a customer or to yourself. Instead give every rate an effective-from date, so new calculations pick up the new rate automatically while old ones stay intact, and run a comparison to see which live quotations are now below cost.

Considerably, which is why one flat figure misleads. Extrusion and weaving waste comes from start-up and edge trim and is usually low. Lamination adds its own start-up and joint loss. Printing is the heaviest, because make-ready, colour matching and cylinder changes scrap finished laminate — the most expensive material in the bag. Cost each process with its own waste and a printed BOPP bag stops looking cheaper than it is.

From coverage, not from a flat allowance. Each colour covers a percentage of the printed area, and ink laid down per square metre depends on that coverage, the substrate and how much solid white is behind it. Multiply area by coverage by the ink laid down, per colour, then add solvent. Nexora has an ink assumption model that reads coverage from the artwork itself and reports how confident it is — see the ink assumption module.

As two articles in one Bill of Materials. The liner has its own lay-flat width, cut length, micron or gauge, its own material rate and its own conversion, and it is inserted as a separate operation with its own labour. Use the LDPE liner weight calculator for the liner weight, then add it as a line in the bag's cost sheet.

It reduces the rate, not the weight, and only up to the percentage your recipe and your customer allow. Cost it honestly: the blended rate is the virgin rate and the reprocessed rate weighted by the recipe, and the recipe has to be the one the plant actually runs, not the one the costing sheet assumes.

You can, and most plants start there. It holds up while one person owns the sheet and rates are stable. It stops holding up when rates need dates, when each enquiry spawns a copy, when waste has to differ by process, and when the costing has to become a purchase plan. At that point the spreadsheet is no longer a calculation, it is six versions of one.

The calculators on this site are free and need no sign-up — the bag costing calculator gives you the weight and shows how the cost is built from example rates. What free tools do not give you is the part that makes costing reliable over a year: your own dated rates, process-wise conversion, component-wise weights, and a costed BOM that carries into production. That is what the desktop app is for.

The weight is close, because geometry is geometry. The money is indicative, because it runs on example rates and common defaults for fold, patch, valve, waste and conversion. A calculator is the right tool to check a quotation or catch a mistake. A quotation you will be held to should run on your own constants, your own dated rates and your own process costs.

The bag weight is yours to read freely. The money and the component-wise break-up are shown on request, because those figures depend on rates and process costs that have to be set up properly to mean anything. Request a demo and we will run your own specification with your own rates.

It should. The costing already knows the kilograms of every material one bag consumes, so multiplying by the order quantity gives the purchase requirement without anybody re-keying it. In Nexora the costed Bill of Materials becomes the production BOM, and the order forecast gives the raw material an order will need before it is accepted.

Whoever is accountable for margin, with the technical team owning the specification. In practice costing sits between sales and production and belongs to neither, which is why it drifts. Putting the constants, the rates and the constructions in one system with roles and approvals is what stops each department carrying its own version of the truth.