Bill of Materials (BOM) Examples and Templates
A bill of materials (BOM) is the source of truth for every part, sub-assembly, and consumable that goes into a product. Get it right and quoting, sourcing, and production run smoothly. Get it wrong and you'll be chasing missing line items for weeks. Below is a practical bill of materials example, plus a template you can copy and adapt to your own products.
What is a bill of materials?
A BOM is a structured list of everything required to manufacture or assemble a finished product. At minimum it identifies each component by part number, describes it, and states how many are needed. Mature BOMs add manufacturer, supplier, unit of measure, reference designator, and cost.
Bill of materials example
Here is a simplified BOM for a small electronic enclosure. The same structure works for mechanical assemblies, furniture, or industrial equipment — only the columns you emphasize change.
| Level | Part No. | Description | Qty | UoM | Manufacturer |
|---|---|---|---|---|---|
| 1 | ENC-1001 | Aluminium enclosure 120x80x40 | 1 | pcs | Hammond |
| 1.1 | PCB-2204 | Main control PCB v2.2 | 1 | pcs | In-house |
| 1.1.1 | MCU-STM32F4 | STM32F411 microcontroller | 1 | pcs | ST |
| 1.1.2 | CAP-100nF | Ceramic capacitor 100nF 0603 | 12 | pcs | Murata |
| 1.1.3 | RES-10K | Resistor 10kΩ 1% 0603 | 8 | pcs | Yageo |
| 1.2 | PSU-5V2A | 5V 2A power supply module | 1 | pcs | Mean Well |
| 1.3 | CBL-USB-C | USB-C cable 1m | 1 | pcs | Generic |
| 1.4 | LBL-SN | Serial number label | 1 | pcs | In-house |
How to structure a BOM
Whether you're building a single-level BOM or a multi-level (indented) BOM, the following columns will cover most quoting and sourcing scenarios:
- Level — 1, 1.1, 1.1.1… shows the assembly hierarchy.
- Part number — your internal SKU, kept stable across revisions.
- Description — human-readable, including key specs (value, tolerance, package).
- Quantity — per finished unit, never per batch.
- Unit of measure — pcs, m, kg, L. Mixing these silently is a classic quoting error.
- Manufacturer / MPN — required for electronic and regulated parts.
- Supplier & supplier part number — who you actually buy it from.
- Reference designator — R1, C4, U2 for PCBs; tags or positions for mechanical assemblies.
- Notes — substitutes allowed, NCNR, lead-time flags, AVL status.
Single-level vs multi-level BOM
A single-level BOM lists every part flat, which is fine for simple products. A multi-level BOM nests sub-assemblies under their parents (see the example above), which mirrors how the product is actually built and makes it easy to cost individual sub-assemblies. If you ever plan to outsource a sub-assembly, use a multi-level BOM from the start.
Free BOM templates
You don't need specialised software to start. Open a spreadsheet, create the columns above, and you have a working BOM template. Two formats cover almost every team:
- Engineering BOM (EBOM) — authored from the CAD or schematic, focused on what the design requires.
- Manufacturing BOM (MBOM) — derived from the EBOM, with packaging, consumables, and process steps that the line actually consumes.
Common BOM mistakes
- Mixing units of measure (e.g. "wire" with no length).
- Leaving consumables (solder, adhesive, labels) out of the MBOM.
- Storing part numbers only in the CAD file, not in a managed list.
- Quoting from a BOM revision that's already been superseded.
- Not flagging long-lead or single-source parts before the quote goes out.
From BOM to quotation with Cataloo
A clean BOM is only half the job — at some point a customer needs a price. Cataloo takes a BOM in the format above (Excel, CSV, or PDF), matches each line against your product catalog, fills in pricing and lead times, and exports a branded Excel or PDF quotation. What used to take a day of copy-paste becomes a few minutes.
- Upload your BOM in the format you already use
- Automatic matching against your product catalog
- Editable pricing, margins, and lead times per line
- Branded Excel and PDF quotes ready to send
Sign up free, upload a BOM, and send a professional quotation today.
Start with CatalooFAQ
What's the difference between a BOM and a parts list?
A parts list is usually a flat enumeration of components. A BOM adds structure (levels, quantities per assembly, units of measure) so it can drive purchasing and production, not just documentation.
What file format should a BOM use?
Excel and CSV remain the most portable. Whichever format you choose, keep one row per part number per level, and never merge cells — automation tools (including Cataloo) rely on a clean tabular structure.
How detailed should a BOM be for quoting?
Detailed enough that every priced line maps to a real, sourceable part. If a line says "fasteners, assorted", it will be priced as a guess.