What is a BOM bill of materials

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Key Components of a BOM

A typical BOM includes several key components:

  1. Item Number: A unique identifier for each component or part.
  2. Part Name: The name or description of the component.
  3. Phase: The stage of the product lifecycle in which the component is used (e.g., design, prototype, production).
  4. Quantity: The number of units required for each component.
  5. Unit of Measure: The standard unit used to quantify the component (e.g., pieces, liters, kilograms).
  6. Procurement Type: Indicates whether the component is manufactured in-house or purchased from an external supplier.
  7. Reference Designators: Used to identify the specific instances of a component within a product.
  8. BOM Notes: Additional information about the component, such as material specifications, vendor details, or manufacturing instructions.
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Types of BOMs

There are several types of BOMs, each serving a specific purpose within the product development and manufacturing process:

1. Engineering BOM (EBOM)

An Engineering BOM (EBOM) is created during the design phase of a product. It lists all the components and materials required to design and prototype the product. EBOMs are often used by engineering teams to communicate design requirements and ensure that all necessary components are accounted for.

2. Manufacturing BOM (MBOM)

A Manufacturing BOM (MBOM) is derived from the EBOM and is tailored for use in the manufacturing process. It includes all the components and materials required to manufacture the final product, along with detailed instructions on how to assemble them. MBOMs may also include information on packaging materials and any sub-assemblies required during the manufacturing process.

3. Sales BOM (SBOM)

A Sales BOM (SBOM) is a simplified version of the BOM used by sales teams to communicate the key components and features of a product to potential customers. It may include high-level information about the product’s materials, dimensions, and functionality, without delving into the detailed manufacturing specifics.

4. Service BOM

A Service BOM is used by service and maintenance teams to identify the components and materials required to repair or maintain a product. It includes information on spare parts, tools, and any consumables needed to keep the product in working order.

BOM Hierarchy

BOMs are often structured in a hierarchical manner, with the finished product at the top and the individual components and sub-assemblies listed below. This hierarchy helps to organize the information and makes it easier to understand the relationships between different components.

Here’s an example of a BOM hierarchy for a laptop computer:

  • Laptop Computer (Level 0)
  • Motherboard (Level 1)
    • CPU (Level 2)
    • RAM (Level 2)
    • GPU (Level 2)
  • Display (Level 1)
    • LCD Panel (Level 2)
    • Backlight (Level 2)
  • Keyboard (Level 1)
  • Battery (Level 1)
  • Hard Drive (Level 1)
  • Chassis (Level 1)

In this example, the laptop computer is the top-level item (Level 0), and the main components, such as the motherboard, display, and keyboard, are at Level 1. The sub-components of the motherboard (CPU, RAM, and GPU) and display (LCD panel and backlight) are at Level 2.

BOM Formats

BOMs can be created and maintained in various formats, depending on the specific needs of the organization and the tools available. Some common BOM formats include:

1. Spreadsheet

Spreadsheets, such as Microsoft Excel or Google Sheets, are widely used for creating and maintaining BOMs. They offer a simple, flexible, and accessible format that can be easily shared and edited by multiple team members.

2. PDM/PLM Systems

Product Data Management (PDM) and Product Lifecycle Management (PLM) systems are specialized software tools designed to manage product information, including BOMs. These systems offer features such as version control, access control, and integration with other business systems, making them ideal for managing complex BOMs in large organizations.

3. ERP Systems

Enterprise Resource Planning (ERP) systems often include BOM management capabilities as part of their broader suite of business management tools. ERP systems can integrate BOM data with other business processes, such as procurement, inventory management, and financial reporting.

4. CAD Software

Some Computer-Aided Design (CAD) software packages, such as Autodesk Inventor and SolidWorks, include BOM management features. These tools allow designers to create and manage BOMs directly within the CAD environment, ensuring that the BOM stays in sync with the product design.

BOM Management Best Practices

To ensure that BOMs are accurate, up-to-date, and effective, organizations should follow these best practices:

  1. Standardize BOM Templates: Develop and use standardized BOM templates to ensure consistency and completeness across all products and projects.

  2. Use Unique Item Identifiers: Assign unique identifiers to each component and sub-assembly to avoid confusion and duplication.

  3. Maintain Version Control: Implement a version control system to track changes to the BOM over time and ensure that all team members are working with the most up-to-date information.

  4. Integrate with Other Systems: Integrate BOM data with other business systems, such as ERP, MRP, and PLM, to ensure data consistency and enable seamless information flow across the organization.

  5. Conduct Regular Reviews: Regularly review and update BOMs to ensure they reflect the current state of the product and any changes in design, materials, or suppliers.

  6. Train Team Members: Provide training to all team members involved in creating, maintaining, and using BOMs to ensure they understand the processes and best practices.

Benefits of Using BOMs

Implementing and maintaining accurate BOMs offers several benefits to organizations:

  1. Improved Communication: BOMs serve as a central source of truth for product information, ensuring that all team members have access to the same accurate and up-to-date data.

  2. Enhanced Efficiency: By clearly defining the components and materials required for a product, BOMs help streamline procurement, manufacturing, and assembly processes, reducing waste and improving efficiency.

  3. Better Inventory Management: BOMs help organizations plan and manage their inventory more effectively by providing accurate information on the materials and quantities required for production.

  4. Reduced Errors and Rework: Accurate BOMs minimize the risk of errors and rework by ensuring that the right components are used in the right quantities and that assembly instructions are clear and complete.

  5. Faster Time-to-Market: By streamlining communication and processes, BOMs help organizations bring new products to market faster and more efficiently.

  6. Cost Savings: BOMs can help identify opportunities for cost savings by optimizing material usage, reducing waste, and enabling better negotiation with suppliers.

BOM Examples

To better understand the structure and content of BOMs, let’s look at a few examples from different industries:

Example 1: Bicycle Manufacturing BOM

Item # Part Name Quantity Unit of Measure Procurement Type
1 Frame 1 Each Manufactured
2 Fork 1 Each Purchased
3 Wheels 2 Each Purchased
4 Tires 2 Each Purchased
5 Handlebars 1 Each Purchased
6 Saddle 1 Each Purchased
7 Pedals 2 Each Purchased
8 Chain 1 Each Purchased

Example 2: Electronics Manufacturing BOM

Item # Part Name Quantity Unit of Measure Procurement Type
1 PCB 1 Each Manufactured
2 Microcontroller 1 Each Purchased
3 Resistors 15 Each Purchased
4 Capacitors 10 Each Purchased
5 LEDs 5 Each Purchased
6 Switches 2 Each Purchased
7 Battery Holder 1 Each Purchased
8 Enclosure 1 Each Manufactured


1. What is the difference between a BOM and a parts list?

A BOM is a more comprehensive document that includes not only the list of parts but also additional information such as quantities, procurement type, and assembly instructions. A parts list, on the other hand, is a simpler document that typically only lists the components required for a product.

2. How often should BOMs be updated?

BOMs should be updated whenever there are changes to the product design, materials, or suppliers. It’s important to maintain version control and ensure that all team members are working with the most up-to-date information.

3. Can a BOM include non-physical components, such as software or services?

Yes, BOMs can include non-physical components, such as software licenses or installation services, that are required for the complete product or system.

4. How do BOMs relate to inventory management?

BOMs provide accurate information on the materials and quantities required for production, which helps organizations plan and manage their inventory more effectively. By integrating BOM data with inventory management systems, companies can ensure they have the right materials on hand when needed, while minimizing excess inventory and waste.

5. What are the challenges in managing BOMs across multiple products or product lines?

Managing BOMs across multiple products or product lines can be challenging due to the complexity of tracking and maintaining accurate information for a large number of components and sub-assemblies. Some common challenges include ensuring data consistency, managing version control, and integrating BOM data with other business systems. To overcome these challenges, organizations should implement robust BOM management processes and tools, such as PDM/PLM systems, and provide adequate training to team members.


A Bill of Materials (BOM) is a critical tool for managing product information and ensuring efficient communication across design, manufacturing, and service teams. By providing a comprehensive list of components, materials, and instructions, BOMs help organizations streamline processes, reduce errors, and improve overall product quality. Implementing best practices for BOM management, such as standardizing templates, maintaining version control, and integrating with other business systems, can help companies realize the full benefits of this essential tool.