What is a BOM in fashion?
A bill of materials: the complete list of fabrics, trims and components, with quantities, needed to make one unit of a product.
In short
A BOM, or bill of materials, is the structured list of every fabric, trim and component needed to produce one unit of a garment, with quantities, specifications and suppliers. It is used to cost the product, order materials and document what the product is made of.
How does it work in practice?
Product developers build the BOM in the PLM system alongside the tech pack. Each line names a material, its colour per colourway, the consumption per garment, the unit of measure and the supplier. Fabric consumption is often first estimated and then confirmed once marker making is done. When a style has several colourways, the BOM shows which trims change and which stay the same.
- Shell and lining fabrics with consumption in metres
- Trims with quantities per unit
- Labels and packaging
- Supplier, price and lead time per item
Why does it matter for fashion businesses?
The BOM drives product costing, so a missing trim or wrong consumption figure directly distorts margin calculations. It also determines how much material is ordered, which affects waste and availability. Increasingly, BOM data is the starting point for fibre composition labels, carbon footprint calculations and future Digital Product Passport content, so accuracy has become a compliance topic as well as a cost one.
How is AI changing it?
AI can draft a first BOM from a sketch or a similar past style, suggest standard trims from a library and spot inconsistencies between the BOM, the tech pack and the costing sheet. Models trained on historical consumption data can estimate fabric usage earlier, before markers exist. These outputs still need review by product teams, but they speed up the early stages considerably.
Common pitfalls
Frequent errors include BOMs that are not updated after sample changes, inconsistent units, and free-text material names that cannot be matched across styles. Using controlled material libraries and locking the BOM at key milestones reduces these problems.
Frequently asked questions
What is the difference between a BOM and a tech pack?
The tech pack is the full technical documentation of a style, including sketches, measurements and construction details. The BOM is the part that lists materials and quantities, and it is often stored as a section of the tech pack.
Why is the BOM important for sustainability?
Fibre composition, material origin and many environmental calculations rely on knowing exactly which materials, and how much of each, go into a product. The BOM is usually the main data source for this.
