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What Is a Bill of Material List?

bill of material list

A bill of materials (BOM) is a comprehensive list that identifies all the raw materials, components and assemblies required to construct or manufacture a product. It also includes the name and description of each item as well as its cost.

A BOM can be single or multi-level, depending on the complexity of the product. A single-level BOM is most appropriate for simple products that don’t require complex processing steps.


A bill of material (BOM) is a comprehensive list of the parts, components, and materials that are required to manufacture a product. It also includes information such as the part’s cost, description, and quantity needed to produce the product. It is commonly used in manufacturing to ensure that all the components are included in the final product. A BOM is a vital part of the product development process and is often used by multiple departments from production planning to inventory management. It can be known by several names, including Product Structure, Assembly Component List, and Material Take-Off in technical production drawings.

The bill of materials provides the primary source of data for product costing, Materials Requirement Planning, and Enterprise Resource Planning systems. It is typically created in a hierarchical format with parent/child relationships. This enables the creation of multi-level and detailed BOMs that can be easily linked together for the purposes of calculating a final product cost and analyzing a supply chain.

During the initial stage of new product development, an engineering or concept BOM is used to provide development, management, and production planning teams with a rough idea of product complexity and price. As the design and engineering process progresses, the BOM will evolve to include more detailed information, which is then passed on for quotes to suppliers. This becomes the engineering BOM, or EBOM, and later, the manufacturing BOM, or MBOM.

While a bill of materials is a comprehensive list of the components and parts needed to make a product, it does not include labor or overhead costs. The bill of materials is a valuable tool for production managers, allowing them to calculate the cost of producing a single unit or an entire batch of items. The information in a bill of materials can also help determine which production methods are most efficient.

When importing an existing bill of materials, the original header total will be changed to match the current price of the inventory item. This will prevent the import from overwriting previous pricing for a particular item. To restore the original header price, right-click on the main invoice line and select Distribute Original Header.


Having detailed descriptions of each part, component or assembly can help to ensure that all the correct parts are ordered. This can also reduce the number of mistakes, which may lead to production delays and costs. The descriptions can include unique identifiers, such as part numbers or SKUs, along with other important information, such as manufacturing process, supplier type, and part status. They can also include a list of alternate suppliers and a description of how a part is used in the assembly process.

There are several different types of bills of materials, but they all share a similar structure. A bill of material (BOM) is a comprehensive list of raw materials, components and assemblies that are needed to make a product. This is a vital document for communication between the store and manufacturing teams. It is a critical source of data for costing, materials requirements planning and other business processes.

A BOM is typically organized in a hierarchical manner, with the highest-level item at the top and the lowest-level item at the bottom. The items are listed in a parent-child relationship, with the raw material or component used as the parent item for each sub-assembly. The descriptions of each item are then populated in the document, which is then used as a reference for the manufacturing process.

In addition to the item number and description, a BOM can contain additional information such as the unit of measure, assembly references, method of parts construction and other notes. It can be displayed using an explosion display or an implosion display, which shows the relationship between each assembly at a higher level and its components at a lower level.

While a BOM is critical for all phases of the production cycle, it’s especially useful in engineering and new product development. It helps to identify the components that will be required for each assembly, and provides a way to determine the cost of each element. It can also be used to help manage inventory, which can improve efficiencies in the supply chain and avoid production delays.


A bill of materials should provide a clear and concise list of the parts and assemblies that are used to make the final product. It should also contain the quantities of each part or assembly required to manufacture the product. This information helps to ensure that the correct quantity of each item is ordered and received. It is also important to specify the unit of measurement in which the item is measured. For example, it may be specified as pieces (pcs), inches (in), kilograms (kg) or liters (l). This information is helpful for determining safety stock and reorder points.

A BOM should include a unique code, description, lifecycle status and approval status for each part. In addition, it should indicate the supplier and vendor for each part or assembly. The bill of materials should also contain the unit cost for each component, assembly or sub-assembly. This information is crucial for calculating standard costs and routings. It can be used for inventory planning, scheduling, material requirements planning and project management.

The BOM structure can be either single or multi-level. A single-level BOM is useful when a product is simple and requires few processing steps or assembly. Each sub-assembly or assembly is shown only once on the BOM and its quantity is listed with each entry. This type of BOM is most commonly used for manufacturing electronics and machinery.

Another common type of BOM is a multi-level BOM with parent/child relationships. This allows for more accurate costing at the raw materials stage. It can also be used to track and monitor changes to the design.

The BOM should also include a reference designator, a unique name that distinguishes one part from another. This is particularly important when a printed circuit board assembly is used in the product. A description of the part or assembly should also be included in the BOM, as well as the manufacturer and specifications.

A comprehensive and well-written bill of materials is essential for any manufacturer. It can help to reduce errors and improve efficiency. A BOM can also be used to estimate material costs, which can help companies plan for future orders and reduce waste. It is also a critical element of any supply chain management system.

Units of Measure

A bill of materials, or BOM, is a document that lists all the raw materials and components needed to make a finished product. It also includes the cost of each component. This information is useful for planning and inventory management, as well as enabling third-party contract manufacturers to accurately calculate production schedules. A BOM is also a useful tool for communicating your requirements to suppliers, as it allows you to provide accurate pricing and delivery lead times.

A BOM is often displayed in a hierarchical manner, with the highest level showing the finished product and each subsequent level displaying the individual components and raw materials. It is important to use the same unit of measure for all parts and assemblies in the BOM, and ensure that the correct quantity is entered for each part or assembly. This will prevent inaccurate purchasing decisions and help you establish safety stock and reorder points.

In a manufacturing BOM, the unit of measurement used to describe each part should be consistent. For example, all parts should be described in the same units, such as pieces (pcs) or kilograms (kg). This will help you keep track of your inventory and avoid stock-outs. In addition, the BOM should include a description of each item, as well as any additional data that may be important to those reading it.

Depending on the type of product, some BOMs may have sub-assemblies. For example, a bicycle manufacturer might create a BoM that includes sub-assemblies such as the frame, hub, and spokes. These sub-assemblies are then incorporated into the broader bike BoM. Similarly, some companies might create separate engineering and manufacturing BoMs.

A BOM is an essential document in any manufacturing process. It helps you track your inventory, forecast your future demand, and identify any inconsistencies in the product design. However, creating and maintaining a BOM is a complex task that requires a lot of time and effort. While spreadsheets may seem like an obvious solution for managing your BOM, they are prone to errors and inaccuracies. They are also difficult to share with other members of your team.