Free Bill of Materials (BOM) Template | Excel Download

What is a bill of materials (BOM)?

If you manufacture anything, from furniture to electronics to industrial equipment, you already know what a BOM is, even if you don't call it that. It's the complete list of everything that goes into making your product: every component, every raw material, every sub-assembly, with exact quantities.

Think of it as the recipe. A finished product is level 0. The major assemblies that make it up are level 1. The individual parts inside each assembly are level 2. And so on, all the way down to the last screw.

Without an accurate BOM, you're guessing at material costs, ordering the wrong quantities, and discovering missing parts in the middle of production. None of those are fun.

Why a well-structured BOM matters more than you think

A bad BOM doesn't stop at procurement; the damage ripples across the entire operation. Production stops because a $2 component wasn't ordered. Your cost estimate is 15% off because the BOM didn't include packaging materials. Your supplier quotes the wrong thing because the specs were outdated.

Here's what a proper BOM does for your business:

• Your procurement team knows exactly what to buy and can generate accurate purchase requisitions without guessing
• You can calculate the true production cost of any product by rolling up all component costs
• No more production stoppages because someone forgot to order adhesive or fasteners
• Engineering, production and procurement all work from the same source of truth
• When there's a quality issue, you can trace it back to the exact component and supplier
• You can request supplier quotes with precise specifications instead of vague descriptions

Types of BOMs

Different teams need different views of the same product. Here's how it breaks down:

An Engineering BOM (EBOM) reflects the design. It's structured the way the engineer conceived the product: functional groupings, design specifications, technical drawings.

A Manufacturing BOM (MBOM) reflects how the product is actually built on the floor. It adds assembly sequence, tooling requirements, and process notes that don't exist in the EBOM.

A Procurement BOM is what the buying team cares about. It groups components by supplier and lead time, making it easy to figure out what to order from whom and when.

A multi-level BOM is hierarchical: product breaks into assemblies, assemblies break into sub-assemblies, sub-assemblies break into individual parts. This is what you need for complex products.

A single-level BOM is a flat list. No hierarchy, no nesting. Works fine for simple products or when you just need a quick reference.

What should a BOM include?

For each component in your BOM, you need enough information for procurement to buy it, engineering to spec it, and production to use it. Here's the minimum:

• Part number: a unique identifier. No ambiguity. "Blue connector" isn't a part number.
• Description: clear enough that someone unfamiliar with the product could identify it
• Quantity per unit of finished product: how many of this component go into each unit you build
• Unit of measure: pieces, meters, kilograms, liters
• BOM level: where it sits in the hierarchy (0 = finished product, 1 = major assembly, etc.)
• Preferred supplier: who you typically buy it from
• Unit cost: reference price for cost rollups
• Lead time: how long the supplier needs to deliver after you order
• Notes: alternatives, criticality flags, special handling requirements

Best format for a BOM

Excel is the standard, and for good reason. It handles multi-level structures, calculates cost rollups automatically, and is universally accessible. Our template gives you four views in one workbook:

• A single-level flat list: quick reference, easy to print
• A multi-level hierarchical view: collapsible structure showing the full product breakdown
• A cost summary: automatic rollup of total product cost from component-level pricing
• A purchase list: components grouped by supplier, ready to turn into purchase orders

How to create a bill of materials step by step

1. Start at the top. Define your finished product as level 0. This is what rolls off the line.
2. Break it into major assemblies. These are the level 1 components, the big building blocks that come together to form the product.
3. Decompose each assembly into its parts. Keep going until you reach individual purchased components or raw materials.
4. Assign quantities carefully. How many of each component per finished unit? Account for manufacturing tolerances and expected scrap rates.
5. Add procurement data: supplier, cost, lead time. This is what turns a design document into a purchasing tool.
6. Validate with every team that touches the product. Engineering checks the specs. Production checks the assembly logic. Procurement checks the supplier data. All three need to sign off.
7. Implement version control from day one. Every change creates a new version with a changelog. BOM discrepancies between engineering and production are one of the most expensive problems in manufacturing.

BOM mistakes that will cost you

The most common BOM error is also the simplest: forgetting components. The big parts rarely get missed. What slips through is the screws, washers, adhesives, labels, and packaging materials. Small items, big problems when you're mid-production and short 10,000 units of a fastener with a 6-week lead time.

Other mistakes to watch for:

• Quantities that don't account for scrap and waste. If your process has a 3% defect rate, build that into the BOM quantities.
• No approved alternatives listed. Single-source components are a supply chain risk. If your sole supplier has a disruption, production stops.
• No version control. Engineering updates the design, production is still working off the old BOM. This happens more than anyone wants to admit.
• Stale data: prices, lead times, or suppliers that haven't been updated in months (or years)
• Ignoring lead time differences. If 90% of your components have a 2-week lead time but one critical part takes 12 weeks, that 12-week part drives your entire planning horizon.

Multi-level BOM: a quick industrial example

Picture an electric pump. Level 0 is the pump itself. Level 1: motor assembly, housing, control board, hardware kit. Level 2 breaks the motor assembly into stator, rotor, bearings and shaft. Each level can be made in-house or purchased, which is exactly why procurement needs the BOM structured, not flat: the buy decisions, lead times and costs attach to specific levels.

In the template, use the level column (0, 1, 2…) and indent child components under their parent. Roll-up cost formulas then compute the true cost per finished unit automatically.

Download your free template

Fill in the form and get a professional BOM template in your inbox. Includes single-level view, multi-level hierarchy, cost summary, and purchase list, all with automatic calculations.

BOM with dozens of components from multiple suppliers?

When your product has 50+ line items spread across 10 different suppliers, manually converting a BOM into purchase orders is a full-day exercise. See how Sourced automates procurement, from materials planning to PO generation to delivery tracking.