A bill of materials (BOM) is a structured list of every component, part, or sub-item that goes into a finished product. In quoting for assembled or configured goods, the BOM defines which items and costs roll up into the quoted price. It answers a basic question before you can quote anything: what exactly is in this product, and what does each piece cost.
How it works
A BOM breaks a product down into its parts, usually with a quantity, a unit of measure, and a cost or price for each line. For a made-to-order desk, the BOM might list the tabletop, four legs, a set of fasteners, and finishing labor. When someone requests a specific configuration, you sum the component costs, apply markup, and arrive at a quoted total. A multi-level BOM nests sub-assemblies inside larger ones, so a change to one part flows up through everything that contains it.
Why it matters for quoting
Products sold by configuration rarely map to a single fixed Shopify variant. The buyer picks options, and the price depends on which components those options pull in. A clear BOM keeps quotes accurate and repeatable, so two people quoting the same build land on the same number. It also makes revisions faster: swap a component, and the roll-up recalculates instead of forcing a manual rebuild.
Applying it on Shopify
When a configured request comes in, you can map the BOM components to Shopify line items and convert the request into a draft order that reflects the real build and cost. That keeps inventory, pricing, and the eventual checkout tied to actual parts rather than a rough estimate. See the B2B quoting glossary for related terms like assembly pricing and cost roll-up, or pricing for plan details.