How to create a bill of materials for your product

A Bill of Materials (BOM) is the complete "recipe" for your product, listing every raw material, part, and sub-component needed to manufacture one single unit. To get started, you must document every item—down to the smallest screw, label, or drop of adhesive—to ensure you can calculate accurate costs and avoid running out of stock during a production run.

Why a BOM is Essential

Think of the BOM as your master reference document. It moves your business away from "guessing" and towards precision. In the UK, where material costs and shipping can fluctuate, having a granular list allows you to see exactly where your money is going and where you might be able to save by sourcing differently.

Steps to Create Your BOM

1. Deconstruct your product: Take your final prototype and virtually (or physically) pull it apart. List every individual piece. Don't forget the "invisible" items like thread, solder, or protective coatings.
2. Identify sub-assemblies: If you pre-make a specific part of your product (for example, a pre-wired circuit board or a hand-stitched handle), list that as a "sub-assembly." You will need a mini-BOM for that specific part too.
3. Specify quantities and units: Be precise. Do you need 20cm of wire, 4 grams of glue, or 2 bolts? Using standard units (ml, g, cm, units) makes ordering from UK suppliers much easier.
4. Include packaging: Many founders forget that the box, the tissue paper, and the "thank you" note are part of the product cost. If it goes out the door with the item, it belongs on the BOM.
5. Add a "Waste Factor": In manufacturing, things break or get trimmed off. If you need 1 metre of fabric but always lose 10cm to offcuts, your BOM should reflect the 1.1 metres you actually use.

Example BOM Structure

Most small businesses start their BOM in a spreadsheet. Here is a simple layout of how it should look:

Part Name	Description	Quantity	Unit	Unit Cost	Total Cost
M4 Bolt	Stainless steel hex head	4	pc	£0.05	£0.20
Oak Plank	Sustainably sourced, 20mm	0.5	m	£12.00	£6.00
Wood Glue	PVA High-strength	10	ml	£0.01	£0.10
Postal Box	Recycled cardboard A4	1	pc	£0.45	£0.45

Pro Tip: Assign a unique "Part Number" or SKU to every item on your list. This prevents confusion when ordering; for example, "Blue Fabric" is vague, but "TEX-BLU-001" is specific and prevents mistakes.

Best Practices

• Keep it live: If a supplier changes their price or you switch from plastic to metal components, update your BOM immediately. An outdated BOM leads to incorrect pricing and lost profit.
• Account for shipping: When calculating the "Unit Cost," try to include the cost of getting that material delivered to your door (landed cost).
• Check for UK standards: When listing materials, ensure they meet relevant UK safety and quality standards, as this will be vital for your final compliance checks.