What is a bill of materials (BOM)? Free template with examples

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21 gennaio 2024
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Like the ingredient list on a recipe card, a bill of materials (BOM) lists what's required to complete a project. Though typically used for product manufacturing, BOMs can benefit software developers, engineers, and even marketing and sales teams. In this guide, we’ll cover the different benefits, types, and best practices for writing your bill of materials.

Have you ever rushed through a recipe—maybe skipped a few steps or omitted some ingredients—and then wondered why it didn’t turn out anything like the picture?

Bill of materials (BOMs) are essentially project “recipe” cards—gather your ingredients, follow the steps to a tee, and you’ve got a deliciously successful end result. Just like your favorite cookie recipe, use a BOM to help organize and lay out the requirements needed to complete a project. 

What is a bill of materials?

A bill of materials (BOM) is an itemized list of materials, components, instructions, and requirements needed to create an end product or deliverable. Though typically used in product development and manufacturing, you can create a BOM for almost any project, from software development to marketing campaigns. 

You will typically create your BOM during a project’s planning phase. But this isn’t something you should do alone. Instead, work with key departments, stakeholders, and external vendors or suppliers to ensure you capture every detail. 

Present your BOMs in a hierarchical format, with the finished product ranking at the primary level and subassemblies, components, and other requirements listed at lower levels. This centralized document helps everyone get on the same page about the exact requirements and timing needed for the project—regardless of launch type.

How does a bill of materials work?

A BOM works by identifying the components and sub-assemblies required to construct higher-level assemblies and outlining their individual parts. This streamlines the process for manufacturers to identify and acquire the necessary components for assembling specific parts.

When it's kept up-to-date and managed effectively, the BOM becomes an indispensable tool for inventory control, sales order management, and improving the efficiency of the production process.

Furthermore, when a BOM is integrated with an organization's enterprise resource planning (ERP) system, it provides instant visibility into the production process. This integration not only streamlines the workflow within ERP systems, but it also empowers managers with real-time updates, alerting them promptly about inventory shortages or the need for item restocking.

Crea un modello di lista dei materiali

Bill of materials formats

When structuring a bill of materials, it's key to understand the two primary formats: single-level BOM and multi-level BOM. These formats are designed to meet various complexities and requirements in product assembly and management. Each format has its strengths and is chosen based on the product's complexity, manufacturing process, and the detail required in the material planning and assembly process.

Single-level bill of materials

The single-level bill of materials is similar to a shopping list, where each component of a product is listed once alongside the required quantity. This simple BOM format is ideal for smaller projects or products with minimal components. 

However, because it doesn't show the interconnectedness between components and subassemblies, the single-level BOM's simplicity can be a drawback for complex products. For example, if a single part fails while building a new product, the single-level BOM will not directly indicate which other parts are affected. This makes troubleshooting more difficult.

Multi-level bill of materials

On the other end of the spectrum is the multi-level bill of materials. This format is a more intricate web that highlights not just the individual parts but also how they interrelate. 

A multi-level BOM includes multiple levels of hierarchy—with the finished product at the highest level and the raw materials and components below—so your team can visually see the relationships between its parts and components. 

This is often described as the parent-child relationship because changes made to the assembly (or parent item) flow to the subassembly (or child item). Because they show these relationships, most complex products use multi-level BOMs.

Furthermore, breaking your BOM into hierarchies will not only help your teams understand what pieces are required for different project phases but also improve change tracking and impact assessment. A well-structured approach is essential for efficient product lifecycle management, which simplifies the entire project workflow.

10 elements of a bill of materials

Whether you’re manufacturing a product or planning your next sales campaign, a BOM can help you acquire exactly what you need to get started.

[inline illustration] What to include in a BOM (infographic)

The data and information included in a BOM will differ from project to project, but in general, most BOMs will include:

  1. Point of contact (POC) information: If a supplier or team member has questions regarding the BOM, include contact information so they can easily get a hold of someone who can help. 

  2. BOM levels: In multi-level BOMs, this is the number identifying where each part or requirement fits within the BOM hierarchy. A finished product would be considered BOM level 1.

  3. Required items: List all of the materials, components, consumables, or parts needed to complete your project, and make sure to add as many details as possible. This may include product names, part numbers, descriptions, quantity, contract manufacturers, suppliers, unit costs, and total cost for each. 

  4. Procurement type: This defines whether the component will be procured in-house or from a supply chain partner or agency. For non-manufacturing BOMs, this is the team responsible for creating each deliverable.

  5. Reference designators: Reference designators are alphanumeric labels used to identify individual components in electronic, medical, and mechanical devices, like printed circuit board assemblies (PCBAs) or complex machinery in the automotive and aerospace industries. Including these details in the BOM saves time and reduces potential confusion in future stages.

  6. Pictures and URLs: Include diagrams, images, or links if applicable. 

  7. Priority: In any project, there are required deliverables and nice-to-haves. Track which is which to protect your project from scope creep. For example, you may want to make note of which components have the longest lead times or highest monetary value so your team knows to pay special attention to them. 

  8. Potential alternatives: If there’s flexibility regarding a component or part, include potential alternatives in case the original isn’t available. 

  9. Revision level: Listing the revision level for your BOM—or a way to identify how many times your BOM has been reviewed and revised—will help stakeholders quickly understand the changes these requirements have undergone. This is typically a simple R1, R2, R3, etc. listed at the top of the BOM. 

  10. Phase: Every product goes through a lifecycle, which can be more efficiently tracked by labeling individual parts according to their current phase. Consider the development of an electric vehicle: during its product design phase, a transition from standard batteries to advanced solid-state batteries could be tracked with labels indicating their phase in the product's lifecycle, from "in design" to "in production."

Read: Product development process: The 6 stages (with examples)

Types of bills of materials

You can implement a bill of materials for virtually any project. As a result, there are a variety of project-specific BOMs. If you’re organizing a complex or cross-functional project, you may need multiple types of BOMs. In this case, each BOM will list the materials and requirements for each component of your project—from design, operations, production line manufacturing, and more. 

Modular bill of materials

Modular BOMs list the materials, documents, parts, and engineering drawings and diagrams you need to complete a subassembly. Use modular BOMs when your deliverables have multiple possible combinations of modules, such as an advertising campaign with various ads showcasing the different benefits of your product or service. 

Configurable bill of materials (CBOM)

If you work in an industry that develops highly configurable products, use a CBOM to list all components required to design and manufacture a product to a client’s specific requirements. You can easily mold and shape these documents to reduce the effort needed to maintain product structures. In order to use a configurable BOM, you must primarily have a modular BOM structure in place.

Engineering bill of materials (EBOM)

An engineering BOM contains the list of items, parts, subassemblies, and assemblies needed to create the finished product. Keep in mind that a single project can have multiple engineering BOMs, such as one for electrical engineering and one for mechanical engineering.

Software bill of materials (SBOM)

Software BOMs list all the open-source and third-party components present in a codebase. This includes the components’ licenses, versions, and patch statuses to help security teams promptly identify any associated risks. To create high-quality, compliant, and secure code, make sure your SBOM is accurate and up-to-date.

Sales bill of materials

Also known as an SBOM in some industries, a sales bill of materials is a comprehensive list of all the components and assemblies needed to build a product based on customers' requests. It typically contains sales order details such as raw materials, production orders, part names, pricing, and labeling, to name a few. 

This type of BOM includes both the completed product and its components as they are recorded in the sales record. 

Manufacturing bill of materials (MBOM)

As the name suggests, a manufacturing bill of materials is used for manufacturing projects. An MBOM tracks all the parts and assemblies required to build a complete and shippable product. MBOMs should list every deliverable and milestone—including items used in the assembly process as well as packaging materials, instructions, and guides shipped with the finished product.

A manufacturing BOM is required before designing enterprise resource planning (ERP) systems and in materials requirement planning (MRP).

Read: What is resource management? Your guide to getting started

Equipment bill of materials

An equipment BOM lists all the replacement spare parts you need to complete your project. This helps maintenance engineers quickly identify, locate, and replace a part. An accurate equipment BOM enables organizations to improve reliability by ensuring the right part is available at the right time.

Read: 6 tactics for scaling resource management to enterprise organizations

How to create a bill of materials

You can create a bill of materials as a static document or a dynamic tool.

Download our static bill of materials framework to effectively manage the fine details and components of your next project. Alternatively, use our dynamic bill of materials blueprint to ensure your entire team is aware of what’s required to complete an accurate, high-quality finished product.

Crea un modello di lista dei materiali

Benefits of using a bill of materials

An accurate BOM is a single source of truth for producing a finished good or deliverable. Without one, you risk a host of problems—think delays due to a lack of inventory, wasted materials, and inconsistent outcomes.

[inline illustration] Benefits of using a BOM (infographic)

Improved transparency

A bill of materials lays out the framework of project requirements for everyone to follow, so teams and suppliers involved in the project are on the same page. This framework helps ensure consistency and simplifies complex processes throughout the project life cycle.

Accurate costing of finished deliverables

BOMs are essential for calculating the accurate costs of deliverables. If you keep the materials and costs up to date in your BOM, it’ll be easy to track the final cost of the finished product—and whether you’re not on track. 

The final cost determines margins, profits, and even taxation levels, so it’s critical that you don’t go over budget. Tracking costs will help ensure your margins remain profitable and prevent scope creep

Improved workflows

A bill of materials gives your team a framework to better plan their workflows. By laying out detailed vital functions in your BOM, you may discover process improvements that boost efficiency and profitability—such as the best time to order or restock inventory to prevent downtime or which teams are best suited for which tasks.

Read: Guide to process mapping: Definition, how-to, and tips

Less wasted resources

With an accurate BOM, you’ll know ahead of time exactly what you need, when you need it, and how much of it to complete your project. This is critical because missing items or deliverables could force you to halt your project until you have all your requirements in place, leading to deadline extensions and increased operating costs. 

In manufacturing, an accurate BOM also improves inventory management since teams will be able to forecast and order the correct quantities of each part of the final product. 

Read: What is resource management? Your guide to getting started today

How to optimize your BOM management

A bill of materials is an extensive document that will require significant time and attention. An effective BOM can improve team communication, collaboration, workflows, and inventory management.

Here are a few general best practices to follow to ensure your bill of materials management is accurate and effective. 

Tailor your BOM to your project's needs

Before creating your BOM, identify what should be included and customize it to the unique requirements of your project. Think of how different industries might use a BOM. 

If you’re building a bicycle, you’d probably include part numbers, quantities, and units of measurement. However, these details wouldn’t apply to a UX BOM for a homepage redesign. 

Be as accurate as possible

You might wonder whether a little detail like glue or fasteners is significant enough to be listed in your BOM. Think about it this way—if you don’t include the requirement in your BOM, it won’t be in the final product. 

Small things can make a big difference in the accuracy of your BOM. Take the time to list as much helpful information as possible to ensure your document is thorough and concise. The more detail, the better. 

Limit editing access

Not everyone involved in a project needs to edit the document. Formalize the process of who has what permissions in order to reduce confusion and human errors. Allow editing privileges only where necessary—you’ll find most people within your organization only need read-only access anyway. 

Track changes

A BOM is a dynamic document, meaning you’ll need to make changes and updates  to it throughout the project lifecycle. However, too many changes and a lack of oversight can lead to inaccuracies and a low-quality end result. 

Develop a system to monitor any changes made to the BOM. This way, you can identify and correct errors before they impact the finished product.

Read: What is a change control process and how do you use it?

Use a template

There will likely be multiple departments and people creating BOMs for each phase of the project, which is why we recommend using a template that is compatible with the group. 

This way, you can implement a consistent ordering process, standardize communication, and still have the flexibility to customize the template to fit your needs. 

Level up your production planning with a bill of materials

No matter your goals, a properly organized BOM lays the foundation for your project's success. To get started, download our template and customize it to best fit your project needs. 

Include all parts, components, requirements, and any other resources you think your team would find helpful—and remember, it’s always better to have more detail than not enough.

Crea un modello di lista dei materiali

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