Bill of Materials in a Tech Pack: A Beginner's Guide

A bill of materials (BOM) in a tech pack is the complete, itemized list of every material that goes into your garment — each fabric, trim, and component, with its placement, supplier, color, and quantity. It’s the part of the tech pack a factory uses to source materials and quote your costs, so a precise BOM is the difference between an accurate quote and a sample that comes back wrong. If you’re new to manufacturing, this is one of the first things a factory will ask you for.

If you’re still getting your bearings on the bigger document, start with our overview of what a tech pack actually is and come back here for the BOM detail.

What is a bill of materials in apparel?

In simple terms, a BOM is a parts list for your garment. If you’ve ever seen the ingredient list on a recipe, it’s the same idea: instead of guessing, the factory reads exactly what’s needed and in what amount.

A trim, by the way, is any non-fabric component that’s added during construction — zippers, buttons, drawcords, labels, elastic, hooks. Fabric covers the main body materials and linings. Together, fabrics and trims make up the full bill of materials. The BOM doesn’t tell the factory how to sew the garment (that’s the construction page) or how big to make it (that’s points of measure) — it tells them what to buy.

What goes in a garment BOM?

A factory-ready BOM lists every material as its own line item with enough detail to source it without emailing you. At minimum, each line should carry:

• Material name and type — e.g. “240 gsm cotton fleece” or “YKK #5 metal zipper.” Be specific; “fabric” or “zipper” alone forces the factory to guess.
• Placement — where it’s used (body, hood lining, side pockets, hem).
• Color / Pantone — the matched color for that component, ideally with a Pantone TCX code so dye lots are consistent.
• Supplier or sourcing note — your preferred vendor, or “factory to source” if you want them to nominate.
• Quantity / consumption — how much per garment (yardage for fabric, count for trims).
• Composition — fiber content and weight (gsm, grams per square meter, is the standard fabric-weight unit).

A small, clear table beats a wall of text. Factories scan BOMs fast, and anything ambiguous becomes a question — or worse, an assumption.

How to build a bill of materials step by step

Here’s the workflow I’d give a designer making their first one:

1. Walk the garment, top to bottom. Physically list every material you can see and touch on your reference sample or sketch — outer fabric, lining, ribbing, thread, zipper, drawcord, eyelets, care label, brand label, hangtag, polybag.
2. Don’t forget the invisibles. Interfacing, fusing, elastic, and even sewing thread are real costs and belong on the BOM. New designers almost always leave thread and labels off.
3. Add specs to each line. Type, weight, color/Pantone, and composition. Pull these from your fabric supplier’s spec sheet rather than eyeballing it.
4. Note placement and quantity. Tie each material to where it lives and roughly how much is consumed.
5. Flag what’s nominated vs. open. Mark which materials you’re supplying or specifying and which the factory can source. This single column saves days of back-and-forth.

Why an accurate BOM saves you money

The BOM is what a factory costs from. Every line is a price the factory looks up or quotes — so an incomplete BOM produces an incomplete quote, and the “extra” costs surface later as surprises. A precise BOM also locks in consistency: when you reorder, the same materials get sourced again instead of a cheaper substitute sneaking in.

It also prevents the most common sampling failure I see: the wrong-substitute sample. You leave the fabric weight off, the factory uses what’s on hand, and your structured jacket comes back floppy. That’s a wasted sample round and weeks of delay — all from a missing line on the BOM. Picking trims and components carefully up front matters for exactly this reason; if you’re building a piece with a lot of hardware, our hoodie tech pack page shows the kind of component detail factories expect.

BOM vs. the rest of the tech pack

It’s easy to confuse the BOM with neighboring sections, so here’s the quick distinction:

• Bill of materials = what goes into the garment (materials and quantities).
• Points of measure = how big the finished garment is, across sizes.
• Construction page = how the pieces are assembled (seams and stitches).
• Colorways = which color versions exist, each with its own matched BOM.

They work together. Change a fabric on the BOM and you may affect the construction and even the measurements — so keep them in sync as your design evolves.

FAQ

Do I really need to list sewing thread and labels? Yes. They’re small but they’re real materials with a cost and a color match, and factories expect them. Leaving them off is one of the fastest ways to get an inaccurate quote.

What’s the difference between a BOM and a tech pack? The tech pack is the whole spec document; the bill of materials is one section inside it. The BOM covers materials, while other sections cover measurements, construction, and colorways.

Should I pick suppliers myself or let the factory source? Either works — just be explicit on the BOM. Nominate suppliers for materials you care about (signature fabric, branded zippers) and let the factory source the rest to save time and cost.

How detailed does a beginner’s BOM need to be? Detailed enough that a stranger could buy the right materials without calling you. Material type, weight, color/Pantone, placement, and quantity for every line is the practical bar.

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You don’t have to build this from a blank spreadsheet. techpacks.app turns a sketch into a complete, factory-ready tech pack — BOM included — within 24 hours, built to a real factory standard. If you’re early in launching a line, our guide for independent designers walks through the whole path. Preview your first pack and see a real BOM laid out for your own garment.