Multi-Level BOM
Understanding bill of materials hierarchy for fashion and apparel — from flat lists to structured component breakdowns that give you full visibility into what goes into every garment.
Joe Lauder·Founder, Kōbō·Updated Apr 22, 2026A multi-level BOM breaks down a product into its complete component hierarchy. For fashion products, this means tracking not just what goes into a garment, but what goes into each component — shell assemblies, hardware kits, label packages — and how they all roll up into the finished product. Where a single-level BOM gives you a flat shopping list, a multi-level BOM gives you the full picture of how a product is actually constructed.
Most fashion brands start with a simple flat list of materials. That works when you have five styles and one supplier. But as products get more complex — outerwear with multiple fabric assemblies, hardware kits sourced from different vendors, packaging specifications that vary by market — a flat BOM stops telling you what you need to know. You lose visibility into where costs actually live, which supplier owns which sub-component, and how a material change in one assembly ripples through the entire product.
A single-level BOM tells you what you need. A multi-level BOM tells you why you need it and where it fits in the product.
What Is a Multi-Level BOM?
A multi-level bill of materials (also called an indented BOM or hierarchical BOM) organizes product components into parent-child relationships across multiple levels. The finished product sits at the top level (Level 0). Below it, major assemblies or groupings form Level 1. The individual materials, trims, and parts that make up each assembly sit at Level 2 and beyond.
Each parent item is made up of its child components. A "Body Assembly" (Level 1) might consist of shell fabric, lining, and interfacing (all Level 2). This structure mirrors how a product is actually built on the production floor — first you prepare sub-assemblies, then you combine them into the finished garment.
Level 0 — The finished product (e.g., Denim Jacket SKU DJ-2025)
Level 1 — Major assemblies or component groups (e.g., Body Assembly, Sleeve Assembly, Hardware Kit)
Level 2 — Individual materials and parts within each assembly (e.g., Shell Fabric, Lining, Buttons)
Level 3+ — Sub-components of Level 2 items, if applicable (e.g., thread colors within a thread kit)
Single-Level vs Multi-Level BOM
Both formats have their place. The right choice depends on product complexity, team size, and how much cost and production visibility you need.
| Aspect | Single-Level BOM | Multi-Level BOM |
|---|---|---|
| Structure | Flat list of all direct components | Hierarchical tree with parent-child relationships |
| Depth | One level only (top level) | Two or more levels of detail |
| Costing | Total cost is a sum of all items | Costs roll up through assemblies, showing where money goes |
| Visibility | What materials you need | What materials you need, organized by where they go |
| Best for | Simple products (t-shirts, basics) with few components | Complex products (outerwear, tailoring) with many assemblies |
| Complexity | Easy to create and maintain | More setup, but far more useful at scale |
| Production | Works as a picking list | Maps to actual assembly sequence on the production floor |
Multi-Level BOM Example for a Garment
Here is what a multi-level BOM looks like for a denim jacket. Level 0 is the finished product. Level 1 groups components into logical assemblies. Level 2 lists the actual materials and parts within each assembly.
Notice how the same material (12oz indigo denim) appears in two different assemblies — Body and Sleeve. A multi-level BOM makes this explicit. When you roll up quantities, you know you need 1.8m total of that denim (1.2m + 0.6m), but you also know exactly where each cut goes. This level of detail matters for cutting plans, consumption tracking, and waste reduction.
Why Fashion Brands Need Multi-Level BOMs
As collections grow and products become more complex, the limitations of flat BOMs become painful. Multi-level BOMs solve four specific problems that every scaling fashion brand encounters.
Accurate Costing
Multi-level BOMs let you see exactly where cost lives in your product. Instead of a single total material cost, you can see that your Hardware Kit costs $4.80 while your Labels & Packaging costs $1.20. This granularity helps you identify where to negotiate, where to substitute materials, and where your margins are thinnest. Rolled-up costing from sub-components eliminates the guesswork that leads to margin erosion.
Production Planning
A factory does not build a jacket from a flat list — they prepare sub-assemblies, then combine them. A multi-level BOM mirrors this workflow. Production planners can see total material requirements across all assemblies, identify long-lead items per assembly group, and schedule work in the correct sequence. If the Hardware Kit supplier needs 6 weeks but fabric needs 4, you know to order hardware first.
Supplier Management
When components are grouped by assembly, it becomes clear which supplier owns which part of the product. Your fabric mill handles the Body and Sleeve assembly materials. Your hardware vendor handles the Hardware Kit. Your trim supplier handles Labels & Packaging. This mapping makes it easier to send targeted purchase orders, manage lead times per supplier, and evaluate supplier performance by assembly rather than by individual line item.
Quality Traceability
When a quality issue arises in production, a multi-level BOM lets you trace the problem back to a specific sub-component within a specific assembly. A button failure is traced to the Hardware Kit, not just "buttons." You know the supplier, the specification, the lot number. This specificity speeds up root cause analysis and helps you decide whether the issue is isolated or systemic across other styles using the same assembly.
Multi-Level BOM Template Structure
Each level of your BOM should contain specific fields. The deeper you go, the more granular the data. Here is what a well-structured multi-level BOM template captures at each level.
| BOM Level | Required Fields | Purpose |
|---|---|---|
| Level 0 | Style number, product name, season, total cost, status | Product identification and top-level cost summary |
| Level 1 | Assembly name, assembly cost (sum of children), primary supplier, lead time | Group components logically, assign ownership, plan timelines |
| Level 2 | Component name, description, supplier, article number, unit, quantity, unit cost, total cost, color, MOQ | Detailed material specs for sourcing, costing, and ordering |
| Level 3+ | Sub-component name, specification, quantity per parent, cost | Needed only for kits or pre-assembled items with their own BOM |
Managing BOMs: Spreadsheets vs PLM
You can build a multi-level BOM in a spreadsheet using indented rows and merged cells. But the experience degrades quickly as you scale beyond a handful of styles.
The fundamental issue with spreadsheets is that they have no concept of relationships. A cell does not "know" it is a child of another cell. Every link between parent and child is a visual convention that breaks the moment someone inserts a row, moves a column, or copies the file. PLM systems enforce the structure automatically.
Frequently Asked Questions
How many levels deep should a fashion BOM go?
Most apparel products need two to three levels. Level 0 is the finished product, Level 1 groups components into assemblies (body, sleeves, hardware, labels), and Level 2 lists the individual materials. You rarely need Level 3 in fashion unless you are working with pre-assembled kits or complex hardware sets that have their own sub-components.
Can I convert a single-level BOM to multi-level?
Yes. Start by grouping your flat list into logical assemblies based on how the garment is constructed. Fabrics and interfacing for the body go into one group, hardware into another, labels and packaging into a third. The same components stay, they just gain a parent. Most PLM systems let you restructure existing BOMs without re-entering data.
Do I need multi-level BOMs for simple products like t-shirts?
Probably not. A basic t-shirt might have 8 to 12 components — fabric, thread, neck label, care label, size label, hangtag, polybag. A single-level BOM handles this well. Multi-level structure becomes valuable when you cross roughly 15 components or when you need to track costs and suppliers by assembly group.
What is the difference between a multi-level BOM and an indented BOM?
They are the same thing. "Indented BOM" refers to the visual presentation where child components are indented under their parent assembly. "Multi-level BOM" describes the data structure with multiple hierarchical levels. Both terms describe a BOM with parent-child relationships across two or more levels.
Joe's the founder of Kōbō Labs. Before this, he founded Satta, a fashion brand he scaled to sell internationally at Mr Porter, SSENSE, and Beams Japan. A decade of running his own brand — design, suppliers, production, the lot — is what Kōbō is built on.
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