A recipe tells you what goes into the product. A bill of materials tells you what leaves your store to make a saleable batch of it — and those are different numbers. The gap between them is yield, scrap and packaging, and it is the reason a plant can follow its recipe exactly and still find the store short at the end of the month.
Most small manufacturers start with the recipe, because the recipe is what the formulator hands over. It is correct as chemistry and wrong as a purchasing document. Closing that gap is usually the single highest-value hour of master-data work a plant can do.
What a recipe leaves out
Take a simple bar soap formulation: so much palm stearin, so much coconut oil, so much caustic, fragrance, colour. The formulation is expressed as percentages of the finished blend, and it assumes every gram that goes in comes out.
Nothing works that way on a real line. Between the raw material bin and the wrapped carton you lose material to:
- Process yield. Saponification, drying, milling and extrusion each shed a little. A noodle line running at 94 percent yield needs 1,064 kg of input for 1,000 kg of output, not 1,000.
- Scrap and rework. Start-up slugs, colour changeovers, the first few bars out of the stamper. Some of it is reworked back in, some is waste, and the two are accounted for differently.
- Packaging. Wrappers, cartons, shippers, labels, pallet stretch. These never appear in a formulation and always appear in a purchase order.
- Sampling. QC retains, retention samples, certificates of analysis. Small per batch, not small per year.
A bill of materials carries all four. A recipe carries none of them.
Yield is a rate, not a constant
The common mistake after discovering yield is to bake a single number into the BOM and move on — 94 percent, applied everywhere, forever. That holds until the plant runs a different pack size, a darker colour, or a shorter campaign, and then it quietly stops holding.
Yield varies with:
- Batch size. Fixed losses — line priming, vessel heels, the material left clinging to the mixer — are the same whether you run 200 kg or 2,000. Small batches carry a much worse yield than large ones.
- Changeover frequency. Five colour changes in a shift costs more than one.
- Product form. A liquid decanted into 5-litre drums loses less than a paste extruded, cut and stamped.
If your BOM supports a fixed loss and a proportional loss separately, use both. If it only supports one figure, set it for your normal campaign size and review it against actual consumption each quarter. The review matters more than the initial number.
Structure it in levels
The second thing a recipe leaves out is structure. A finished good is not one flat list of raw materials; it is usually two or three levels deep.
For a bar soap plant the levels are typically:
- Base — oils, caustic, water. Made in campaigns, stored as noodles or billets, consumed by many finished goods.
- Blend — base plus fragrance, colour, actives. Specific to a variant.
- Finished good — blend plus wrapper, carton, shipper, for one pack size.
Flattening this into a single list feels simpler and costs you the ability to answer the two questions you will be asked most: how much base do we need next month across all variants, and what does it cost us to make a tonne of it. Keep the levels. A well-structured BOM lets the same base feed fifteen finished goods without fifteen copies of the same oil quantities drifting apart.
What good looks like
A bill of materials is doing its job when three things follow from it without anyone doing arithmetic by hand:
- Material requirements. Given a production plan, the system lists what to buy and when, net of what is already in stock. This is the whole point of the structure above.
- Batch costing. Standard cost per unit that reflects real consumption, not recipe percentages — so when someone asks whether a line is worth running, the answer is grounded.
- Traceability. When a batch consumes lot-tracked materials, the BOM is what links the finished lot back to the raw lots that made it. Export buyers ask for that chain; see lots, retest dates and FEFO for what they expect it to look like.
In Aourix, formulations and their material dependencies sit in the Products area and feed Production and Procurement directly — the plan reads the structure rather than a person retyping quantities into a purchase request. The structure is the work; the software's job is to stop you keeping a second copy of it.
Start with your three biggest sellers
You do not need to convert every SKU before this pays off. Take the three products that account for most of your volume and, for each, write down: the formulation as the formulator gave it, the actual input quantity from the last three production records, and the packaging consumed. The ratio between the first two is your real yield. The gap will usually surprise you by more than you expect, and it is the number your purchasing has been missing.