What Is Bill of Materials?


In this article, we’ll learn the ins and outs of creating a bill of materials (BOM), including every detail you should list on your BOM. Then, we’ll reveal some best practices that can help your business create a better BOM and discuss how inventory management software can help your business track all the raw materials, components, and parts needed to manufacture finished goods and easily craft bills of materials. 

Bill of Materials Definition

A BOM, or a “bill of materials,” is an itemized list of every single raw material, part, and component needed to manufacture a product. A BOM also lists how much of each item is required and even includes secondary requirements like manuals, guides, and packaging.

But a BOM does not explain how certain materials are used or in what order. Still, many manufacturers choose to write BOMs in an orderly fashion to reduce confusion. 

From a more zoomed-out view, a bill of materials is a component of a manufacturer’s bill of resources (BOR)—an exhaustive list of all that’s required to create a finished good for sale, including labor.

Exactly how a BOM is formatted depends on several variables, including what’s being manufactured and how. There are usually two versions of bills of materials: the EBOM (engineering) and the MBOM (manufacturing). The EBOM is used while the product is still being created, developed, and redeveloped. Once a product is in production mode, an MBOM is used.

One note: EBOM sometimes stands for an equipment bill of materials, too. An equipment bill of materials identifies all the components, parts, assemblies, and subassemblies of a piece of equipment. An EBOM might be used by repair people during equipment maintenance or malfunction to figure out what’s where, and what parts may need to be replaced or repaired, and how.


How do you make a BOM (bill of materials)?

To write a bill of materials, you’ll need to access a lot of particular information about your inventory. If you track details about your raw materials, components, and parts in inventory management software, you can pull data for your BOM directly from that software. Here are some of the things you’ll want to include on your bill of materials:

BOM level

The best bills of materials are sensibly organized. A BOM level quickly illustrates where a part or assembly fits within the bigger picture. The point of this number is to help any reader make sense of each and every part of the BOM.

Assigned part number

Manufacturers number every single piece or part used in a BOM so that referencing and identifying parts is fast and foolproof. Your company can decide whether to make those numbers intelligent (usually a serial number with no significance) or intelligent (perhaps a meaningful, alphanumeric code similar to an SKU.) You can also use an inventory ID, such as the one Sortly automatically issues when you create an item. 

Whichever method you choose, an assigned part number will serve as a “key” to your BOM.

Unique part name

While your BOM will already have assigned part numbers, you’ll want to ensure each item also has a unique part name. This will help give context to part numbers and give BOM readers even more valuable information. 

Lifecycle phase

If you’re still in the iterative engineering phase of manufacturing, ensure to denote what lifecycle stage each part is in. For example, some parts might be “unreleased” or “prototype only,” where others might be “in design,” “in production,” or “ready to manufacture.”

These designations can help your team clear up confusion, create more realistic manufacturing timelines, and get a quick-but-detailed update on the project’s status. 

Detailed description

A detail-rich description of a part, component or raw material can help reduce human error by differentiating parts that may look or sound alike. That’s especially true at larger companies where the manufacturers may not work alongside engineers or inventory specialists.


A BOM doesn’t just list what’s needed to manufacture a product, but how much of it. So be sure to list the quantity used during assembly clearly. 

Detailed unit of measure

While not a requirement, it’s wise to provide a detailed measure unit for every raw material, component, or part on your BOM. Ensure to use the same unit of measure you use to purchase and produce your finished goods. While it’s not always possible, try to choose a consistent unit of measure to reduce confusion. 

Procurement details

How you procure your raw materials, components, and parts matters. For example, do you buy glue pre-fabricated, or is it custom-produced for your business? Or does your business make it in-house? These notes, which you likely already store in your inventory app, should be included on your bill of materials. 

Reference designator

Your product may include PCBAs, also known as printed circuit board assemblies. If that’s the case, ensure you also provide reference designators that indicate where those parts belong in your BOM. PCBAs can be some of the most confusing aspects of manufacturing, so providing this information right off the bat can save time, money, and stress. 

Other unique details that matter for your business

Finally, you should include any other notes that matter to you, your team, and anyone else who plans for or helps produce finished goods. This includes unusual lead times, ordering instructions, hazard warnings, and more. 

Experience the simplest inventory management software.

Are you ready to transform how your business does inventory?


Bill of materials: Best practices

Creating a detail-rich bill of materials is essential, but there are even more best practices that can help you optimize your BOMs. Here are four best practices to consider.

1. Know what you’re making

There’s really no need to begin a BOM until you’ve started designing your finished good. Sure, that design might evolve, but until you’ve got a pretty good idea of what your end product will look like, it’s hard to create an accurate BOM. 

Once you’ve got a pretty good idea of what you’re making, you can create your EBOM (engineering bill of materials). And once you’re ready to create a finished product, it’s time to develop your MBOM (manufacturing bill of materials).

2. Stay flexible and organized as your BOM evolves

When you’re in the iterative engineering phase, your EBOM will evolve constantly. The raw materials, parts, and components you use will change as you optimize and reimagine your product over and over again. That’s okay—just keep updating your BOM every time you make a change. 

Once you move onto an MBOM, you’ll find that you’ll still need to update your bill of materials from time to time. Maybe that’s because you’ve switched suppliers, upgraded a part, or need to comply with new environmental standards.  

3. Remember to attach essential documentation

There may be important components to your manufacturing process that you need to include in your BOM. For example, from CAD drawings to subassembly instructions for certain components, ensure you include this information with your BOM. 

It is better to include a little too much information than risk your manufacturer not understanding what they need to complete the project. 

4. Don’t overlook the little things

From glue to string to bubble wrap, there are lots of tiny components that turn raw materials and parts into ready-to-sell products. When creating your BOM, keep an eye out for the little things your team may have overlooked. An experienced manufacturing partner can also review your BOM, and perhaps help you identify something you might have missed. 


How does Sortly inventory software help businesses create BOMs?

Sortly inventory management software makes it easy to create a BOM by digitizing and centralizing all of your inventory data in one easy-to-use platform. Beyond just tracking finished goods, Sortly excels at tracking parts, supplies, and materials you might include in a BOM. You’ll have every detail about your inventory recorded in Sortly—price, cost, location, quantity, unit of measure, manufacturer, and much more—which will make creating a BOM simple and streamlined. Additionally, your entire team can manage inventory in real time from any device or location—even on the manufacturing floor—which makes it easy to put your BOM into practice.

If your company would benefit from improved inventory management, try Sortly free for 14 days. Sortly lets you organize, track, and manage your inventory—from any device, in any location. Our easy-to-use mobile app lets you and your team update inventory on the job, scan barcodes from your smartphone, set low stock alerts to remind you to re-order, and more. That means you can work more efficiently, plan for jobs better, and serve your customers to their highest satisfaction. Join the over 30,000 professionals who trust Sortly as their inventory management solution and start your trial today.