Bulk ingredients and COGS: unit costs for small makers

Makers often buy raw materials in bulk-wax by the slab, fragrance by the bottle, flour by the sack-then use small amounts per finished unit. Your books need a per-use cost, not just the receipt total, or your margins will lie to you.

Pick one honest base unit

Choose the smallest unit you will actually measure in recipes: grams, millilitres, pieces, or metres. Everything else converts into that base. The goal is stable math, not scientific perfection on day one.

• If you buy 5 kg and work in grams, your base is grams; the purchase price spreads across 5,000 g.
• If you buy 50 sheets and use “per card”, define what one sheet yields.
• Round consistently; tiny rounding error beats paralysis.

Turn a purchase into a unit cost

Divide what you paid (including shipping and duties you consider part of landed cost) by how much usable material you received. That gives cost per gram, per ml, or per piece. When a recipe says 200 g of wax, multiply 200 by the per-gram cost to get ingredient COGS for that unit.

When purchase size changes

Update the unit cost when your supplier or pack size changes. Old averages feel safe but they quietly erode margin. A quarterly review of top ingredients is enough for most small studios.

Why this matters at events

Event pricing is emotional-crowds, weather, competition-but your floor should still reflect reality. If you know COGS per finished good, you can discount intelligently or walk away from a race to the bottom.

OpenInventory’s production stock model is built around purchase cost and base units so analytics can relate sales back to materials. Explore it in the production stock demo.