Item Master, BOM and Recipes: A Standardization Method (2026)

What is a Bill of Materials (BOM)?

A BOM lays out every component a product needs, and how those components stack up into the finished item.

A Bill of Materials (BOM) is the full list of raw materials, semi-finished goods, components, and sub-assemblies that go into a finished product. But calling it a list undersells it. A BOM is really a hierarchy: it shows how the product is put together, layer by layer.

Core Components of a BOM

• Parent: The main product being manufactured or the intermediate sub-assembly
• Child/Component: The materials required to create the parent
• Quantity: How many of each child component are needed
• UoM: Unit of Measure (pieces, kg, meters, liters, and so on)
• Level: The position in the BOM hierarchy (0 = finished product)
• Scrap: The percentage of loss you expect during production

Why is the BOM Critical?

The BOM is the spine of a manufacturing operation. Nearly everything downstream leans on it:

• MRP (Material Requirements Planning): What material is needed, when, and in what quantity?
• Costing: Product costs are calculated from the BOM
• Procurement: Material orders are generated according to the BOM
• Production Planning: Work orders are opened based on the BOM structure
• Inventory Management: Reservations and allocations are tied to the BOM

How complex a BOM gets depends heavily on the industry. A furniture maker might get by with 20 to 50 components per product; a machine builder can be looking at thousands.

Material Coding System and Coding Plan

When every material carries a consistent code, your systems finally speak the same language.

Your coding system is simply how you hand every material, semi-finished good, and finished product a unique identity. Get it right and integration between systems gets easier, duplicates stop piling up, and your reports actually add up. Get it wrong and you spend years fighting the mess.

Coding Approaches

1. Intelligent/Significant Coding

The code carries information about the material:

• Example: SCREW-M8-25-SS (Screw, M8 external, 25mm length, stainless steel)
• Advantage: You can read the material straight off the code
• Disadvantage: Change the coding structure and every code has to be reworked; codes get long, and flexibility is limited

2. Non-Significant Coding

The code is just a unique identifier and carries no meaning:

• Example: 100001, 100002, 100003…
• Advantage: Flexible, resistant to changes, short
• Disadvantage: You can’t tell what the material is from the code alone; you need the system to look it up

3. Hybrid Approach

Categorical prefix + sequential number:

• Example: RM-100001 (Raw Material), SF-200001 (Semi-Finished), FP-300001 (Finished Product)
• Advantage: Easy to filter by category, with reasonable flexibility

Coding Plan Design

Before you settle on a coding plan, work through these questions:

• How many digits will the code have? (Typically 6-12)
• Numeric or alphanumeric?
• Will you use a category prefix?
• What are the rules for automatic number generation?
• Will deleted codes be reused? (The answer should be no.)

BOM Types: EBOM vs. MBOM

Engineering sees the product one way, the factory sees it another—hence two BOMs.

Different departments look at product structure from different angles, which is exactly why more than one BOM type exists:

Engineering BOM (EBOM)

Product structure from a design and engineering perspective:

• Can be generated automatically from CAD systems
• Organized by functional groups (electrical group, mechanical group, and so on)
• Includes all design components
• Does not contain production process details

Manufacturing BOM (MBOM)

Defines how the factory will actually build the product:

• Includes work stations and the sequence of the production process
• Phantom items and sub-assemblies are defined to match the production flow
• Includes scrap rates and alternative components
• MRP and production planning run off this BOM

Transition from EBOM to MBOM

Turning an EBOM into an MBOM is one of the jobs production engineering lives or dies by:

1. Production process analysis: In what sequence and at which stations will it be produced?
2. Sub-assembly groups: Which sub-groups get built separately and then joined?
3. Make vs. Buy decision: Which components will you produce, and which will you buy?
4. Alternative component definition: Are there substitute materials?
5. Scrap and loss rates: What losses do you expect during production?

Other BOM Types

• Service BOM: After-sales service and spare parts perspective
• Sales BOM (Kit): Grouping of products sold together
• Configurable BOM: For products with options and configuration-based requirements

Multi-Level BOM Structure

Simple products can be managed with a single-level BOM. Most manufacturers, though, end up needing multi-level structures.

BOM Levels

• Level 0: Finished product (the final product to be sold)
• Level 1: Main sub-assemblies and their direct components
• Level 2: Components of sub-assemblies
• Level 3+: More detailed sub-components
• Lowest level: Purchased raw materials

Level Count Optimization

Pile on too many levels (10+) and problems follow:

• MRP calculation time increases
• Planning complexity increases
• The number of work orders balloons
• Traceability becomes difficult

Too few levels (1-2) causes its own trouble:

• Intermediate stocks can’t be tracked
• Cost can’t be distributed properly
• Modular production isn’t supported

Criteria for Level Design

Only add a new level when at least one of these holds true:

• The intermediate product will be kept in stock (a real stock point)
• The intermediate product can be purchased or sold separately
• It is produced at a different work station or department
• A quality control point is required
• There is a genuine need for cost tracking and reporting

Management of Phantom Items and Intermediate Components

A phantom item is an intermediate component that helps you organize the BOM hierarchy but never actually sits in stock.

When to Use Phantom Items?

• The sub-assembly moves straight to the next stage the moment it’s built, so it’s never stocked
• The grouping exists purely to organize the BOM
• You don’t want MRP creating a separate work order for it
• You need the grouping for costing, but no stock will be held

Phantom Item Behavior

When MRP hits a phantom item, here is what happens:

1. It doesn’t create a separate work order for the phantom
2. It “explodes” the phantom’s sub-components up to the parent level
3. Material requirements are calculated from the real components sitting beneath the phantom

Recipe Management

In process industries (food, chemical, pharmaceutical), the recipe plays the role a BOM plays in discrete manufacturing:

• Formula: Raw material ratios and mixing rules
• Co-product: By-products that emerge during production
• By-product: Lower-value secondary outputs
• Batch sizing: Batch size and scaling rules

Defining Alternative Components

Build alternative components into the BOM so supply hiccups don’t stop the line:

• Primary and secondary supplier materials
• Substitute material rules
• Priority order and selection criteria
• Cost difference calculation when an alternative is used

Field Example: Machinery Manufacturer

Real Case (Brand-Neutral)

Situation

An industrial machinery manufacturer with 85 employees. 12 different machine models, each averaging around 1,500 components. Where they started: BOMs living in Excel, every engineer running their own coding system, duplicate material cards everywhere, and an MRP nobody trusted.

Steps Taken (representative duration: 6 months)

1. Months 1-2: Existing material cards were inventoried and duplicates flagged (8,500 total cards, 2,100 duplicates)
2. Months 2-3: A new coding plan was designed (hybrid approach: category prefix + 6-digit sequential number)
3. Months 3-4: BOM levels were redesigned, phantom items were defined, and the EBOM-MBOM split was drawn
4. Months 4-5: Alternative components and scrap rates were defined
5. Months 5-6: Data migration and MRP testing were completed

Result (representative)

• Number of material cards: 8,500 → 6,400 (25% reduction after merging duplicates)
• Average BOM level: 8 → 5 (optimized with phantom usage)
• BOM accuracy: 72% → 96% (representative improvement)
• MRP reliability: unplanned material shortages down 60%

7 Most Common Mistakes in BOM Management

1. Creating Duplicate Material Cards

“I couldn’t find it, so I made a new one.” That mindset is the number-one offender. The same material ends up under two or three codes, inventory and cost data splinter, and MRP does its math on the wrong numbers. Keep the authority to create materials in few hands.

2. Not Defining Scrap Rates

If the losses that happen on the floor never make it into the BOM, MRP will chronically under-order. Scrap rates matter most in cutting, drilling, and chemical processes, where the waste is real and predictable.

3. Using the EBOM Directly as the MBOM

An engineering BOM wasn’t built with production in mind. It has no phantom items, no production sequence, no alternative components. Converting EBOM to MBOM has to be a standing part of the process, not an afterthought.

4. Not Implementing BOM Versioning

Change the design and the old BOM just vanishes. Which order was built to which version? When a quality issue surfaces months later, you have no way to trace it back.

5. Creating Too Many Levels

Spinning up a separate level for every little sub-group inflates work orders and drags MRP down. If a level isn’t a real stock point or a real production decision, make it a phantom.

6. Neglecting Unit Conversions

Procurement buys in kg, the BOM is written in meters, inventory counts in pieces. Get the conversion factors wrong and every downstream calculation inherits the error.

7. Not Assigning BOM Ownership

Who owns the BOM: engineering or production? A BOM without an owner is data nobody answers for, and it quietly rots. Name a data owner and make it stick.

A disciplined BOM process is what keeps these mistakes from ever surfacing.

Success Metrics

To gauge how BOM management is actually going, track the metrics below (values shown are representative):

Adapt these to your own operation and pull a tracking report every month.

BOM Management Checklist

You can adapt this checklist for your sector-based projects as well.

Frequently Asked Questions (FAQ)