A bill of materials (BOM) is the list of every part on your board. A clear BOM gets you the right parts the first time; a vague one leads to substitutions, questions and delays.
Columns to include
| Column | Example | Why it matters |
|---|---|---|
| Designator | R1, R2, R5 | Links the part to the board |
| Quantity | 3 | Per board |
| Value | 10k, 100nF | The electrical value |
| Package | 0805, SOT-23 | Must match your footprint |
| Key ratings | 1%, 50 V, X7R | Tolerance, voltage, dielectric, power |
| Manufacturer | Yageo | Removes ambiguity |
| Manufacturer part number | RC0805FR-0710KL | The exact part |
| Notes | DNP, alternates allowed | Assembly and sourcing instructions |
Write values so they can't be misread
- Use the letter as the decimal point:
4k7,4R7,2M2. See how to read resistor values. - Write capacitor values with their unit prefix:
100nF,10uF,22pF. Avoid mixing0.1uFand100nFfor the same part in one BOM. - Never leave a capacitor as just "100nF". Add voltage, dielectric and package:
100nF 50V X7R 0603.
Group identical parts
Put every identical part on one line with all its designators (R1, R2, R5) and a total quantity. It makes the BOM shorter, makes price breaks visible, and exposes near-duplicates — such as 10 kΩ 1% on one line and 10 kΩ 5% on another — that you can merge into a single part.
Give a part number where it matters
For generic passives, a full description is often enough and lets a supplier offer what is in stock. For ICs, connectors, crystals, inductors and anything with a specific footprint or behaviour, always give the manufacturer part number. Two parts with the same headline value can differ in pinout, package or performance.
Say what can be substituted
State which lines accept alternates ("any 1% 0805 thick-film") and which must be exact. This is the single biggest factor in how quickly a BOM can be quoted and filled.
Check before you send
- Does every footprint on the PCB match the package in the BOM?
- Are capacitor voltage ratings at least double the rail they sit on?
- Are polarised and orientation-sensitive parts clearly identified?
- Are unpopulated parts marked DNP (do not populate)?
- Have you added spares for small, cheap parts that are easy to lose?
- Is each part's quantity the per-board number, with the number of boards stated separately?
Send us your BOM
You can search for each line in the store — the search accepts values like 10k 0805 and manufacturer part numbers. For a full BOM or bulk quantities, send it through the contact form and we will quote it, including parts we source to order.