Bill of materials template

What is a bill of materials?

A bill of materials (BOM) is the list of everything that goes into one finished item: each part, sub-assembly and raw material, with the quantity needed and where it comes from. Production uses it to build, purchasing uses it to buy, and estimating uses it to cost a quote.

What should a bill of materials include?

Each line needs a part number, description, quantity, unit, make or buy, supplier and cost. A header says which item and drawing revision the BOM is for, so nobody builds or prices from an old one.

1. 01Level: 0 for the finished item, 1 for parts that go straight into it, 2 for parts inside those.
2. 02Part number and description: your own number, and enough words to tell it apart from similar parts.
3. 03Qty per and total qty: how many go into the part above, and how many that makes for one finished item.
4. 04Unit: each, metres, kilograms or whatever you buy it in.
5. 05Make or buy, and supplier: who makes it, or who you buy it from.
6. 06Unit cost and line cost: the cost of one, and the total for one finished item.

The bill of materials template

Start with the finished item at level 0, then list what goes into it.

Bill of materials example

This one is a small bracket assembly: two machined brackets made from cut aluminium blanks, fitted with dowel pins and cap screws, and labelled. Material and bought-in parts come to £6.79 an assembly, before machining or assembly time.

What's the difference between a single-level and a multi-level BOM?

A single-level BOM lists only the parts that go straight into the finished item. A multi-level, or indented, BOM also shows what goes into each of those parts, level by level, so a made part's own material sits under it. Use multi-level when you make sub-assemblies, so nothing gets bought or costed twice.

What's the difference between an engineering BOM and a manufacturing BOM?

An engineering BOM lists the parts as the designer drew them. A manufacturing BOM lists what the shop needs to build the item in your works, including blanks, consumables, packaging and the way sub-assemblies are made. Cost quotes and raise purchase orders from the manufacturing BOM.

How does a BOM help you quote?

The BOM gives the material and bought-in cost of one item, which is the first half of any estimate. Add the machine and labour time from the routing, outside processes such as anodising, and your margin, and you have the basis of a price. Keep BOMs current, so each quote starts from today's costs.

The quotation template picks up from there.

Can AI build a bill of materials?

AI can draft a BOM from the parts list on a drawing or a customer's assembly drawing, and fill in descriptions and suppliers from your past BOMs. A person checks the quantities, the levels and anything it couldn't read, because a wrong quantity flows straight into the price and the purchase orders.