What are the 4 types of inventory?

The four types of inventory are: raw materials (inputs you'll transform — fabric, components, ingredients), work-in-progress (WIP — partially finished goods on the production floor), finished goods (sellable products, the type most retail and ecommerce businesses mean by 'inventory'), and MRO — maintenance, repair and operations supplies (spare parts, packaging, cleaning supplies — things you consume but don't sell).

Why the split matters: each type ties up cash differently and needs different tracking. Finished goods drive reorder points and sales forecasting; raw materials follow production schedules; WIP exposes production bottlenecks; MRO quietly disappears unless someone tracks it.

A pure reseller may only carry finished goods (plus packaging as MRO). A maker or light manufacturer carries all four — and usually discovers the value of separating them the first time a build stalls on a missing $2 component.