Bill of Materials Definition
A Bill of Materials (BOM) is a structured list of all the components, parts, and materials required to manufacture or assemble a finished product, including the quantity and relationship of each item.
A BOM is the authoritative record of what a product is made of. It sits at the intersection of product management, procurement, and manufacturing, and is one of the most data-intensive documents a manufacturer maintains.
What does a BOM typically include?
- Part number and name — a unique identifier and description for each component
- Quantity — how much of each component is needed per finished unit
- Unit of measure — whether the quantity is counted in pieces, meters, kilograms, or another unit
- Level or hierarchy — where each component sits in the assembly structure, from raw material up to finished good
How does a BOM relate to product data management?
In a manufacturing context, the BOM is often managed in an ERP system, where it drives purchasing, production planning, and cost calculation. When product data is also managed in a PIM, the two systems need to stay aligned: the ERP owns the BOM structure while the PIM manages the customer-facing content built around it. Keeping these in sync is a common integration challenge for manufacturers selling direct or through digital channels.
What is the difference between an engineering BOM and a manufacturing BOM?
An engineering BOM (eBOM) reflects how a product is designed, listing components as defined by the engineering team. A manufacturing BOM (mBOM) reflects how the product is actually built, which may differ due to substitutions, production sequences, or packaging requirements. Both versions may exist simultaneously and need to be managed separately.
