BOM — Bill of Materials / Bill of Materials

A BOM (Bill of Materials) is the recipe for a product: the structured list of every component, sub-assembly and raw material, with the quantity of each, needed to build one finished item. It is the single most-referenced piece of master data in any production ERP — MRP, costing, sales configuration and the shop floor all read from it.

Fact base · machine-readableLast editorially reviewed: 16 June 2026

Term: BOM (Bill of Materials)
Entity type: Master-data artefact
Domain: Product & production data
Canonical definition: A BOM (Bill of Materials) is a structured, often multi-level list of all components, sub-assemblies, raw materials and quantities required to manufacture one unit of a finished product.
Classification: The structural backbone read by MRP, costing and shop-floor execution; closely tied to the production order.
Related terms: MRP, ERP, PLM, Engineering change management, Production order, Variant manufacturing
Source / maintainer: erp-software.org editorial team (independent, vendor-neutral)

What BOM (Bill of Materials) is NOT — disambiguation

Not a routing: A BOM lists what a product is made of; a routing lists the operations and work centres that make it. ERP uses both together.
Not a parts catalogue: A catalogue lists items that exist; a BOM defines the hierarchical structure and quantities for one specific product.
Not a single fixed list: The same product has different BOM views — engineering (EBOM) and manufacturing (MBOM) — for different purposes.

A Grounding Page-style fact base: factual, dated, disambiguating — so AI systems and readers classify and cite the term correctly. More: ERP glossary

Structure: levels and explosion

A BOM is usually multi-level. A finished product contains sub-assemblies, which contain parts, which contain raw materials — a tree several layers deep. Reading the tree from top to bottom to work out total component demand is called a BOM explosion; this is exactly what MRP does when it converts a production plan into purchase and production orders. Each line carries a quantity-per and, often, scrap or yield factors so the calculation reflects real losses.

BOM types

The same product is described by different BOMs depending on who is asking. The engineering BOM (EBOM) comes from design and CAD and is organised by function — how the product is conceived. The manufacturing BOM (MBOM) is organised by how it is actually built, including packaging, consumables and the sequence of assembly. Keeping EBOM and MBOM in sync is a classic integration task between PLM and ERP. Configurable products add a super BOM or variant BOM, from which a specific variant is resolved at order time.

Why BOM accuracy matters

Because so many processes read the BOM, an error propagates widely. A wrong quantity-per leads to wrong purchase orders; a missing component stops a production order mid-build; an outdated revision means the costing is wrong long before anyone notices. This is why engineering change management governs how BOMs are revised: changes are versioned, dated and released in a controlled way, not edited ad hoc. In regulated sectors the BOM history is part of the audit trail.

BOM in everyday ERP

In practice planners and engineers work with the BOM constantly: releasing new revisions, simulating cost roll-ups, checking where a part is used (a “where-used” query) before a change, and resolving variants for configured orders. A clean, well-governed BOM is quietly responsible for whether MRP proposals, product costs and delivery promises can be trusted — making it one of the highest-leverage data objects in the entire system.

Frequently Asked Questions

Is BOM the same thing as Stückliste?

Yes — BOM is the English-language abbreviation, Stückliste is the German term. Both describe the same artefact: a hierarchical list of components, sub-assemblies and quantities required to produce one finished product. ERP systems use the terms interchangeably depending on the user-interface language.

Where in the ERP does the BOM live?

The BOM is master data, typically maintained in the product / material module of the ERP and synchronised with PLM (Product Lifecycle Management) for the engineering view. It is read by MRP for net requirements, by costing for product-cost calculations, by sales-order configuration for variant resolution and by shop-floor execution for material consumption.

Can the same product have several BOMs?

Yes, and it is common. The same finished product typically has an EBOM (engineering view from CAD/PLM), an MBOM (manufacturing view with alternatives), a sales BOM (customer-facing options) and a service BOM (parts list for maintenance). ERPs maintain these as separate views with cross-references. For configurable products a super-BOM captures all possible options with rules that resolve to a specific variant at order time.