What is a Subassembly? Examples for Handmade and Small-Batch Makers
A subassembly is an intermediate product you make before it becomes part of a finished good. Learn what that means in practice — with examples for candle, soap, and jewellery makers.
When you start building out a bill of materials for your products, a few terms pop up that aren’t always explained clearly. “Subassembly” is one of them.
It sounds technical — and in large-scale manufacturing, it can get complicated. But for handmade and small-batch makers, the idea is actually pretty simple. And once you understand it, you’ll find it solves a real problem you’ve probably already run into: re-entering the same group of materials over and over across different product recipes.
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What is a subassembly?
A subassembly is an intermediate manufactured product — something you make as part of your production process, before it becomes part of a larger finished product.
It’s not a raw material (you don’t buy it from a supplier). It’s not a finished product (you don’t sell it to customers, at least not on its own). It sits in the middle: you produce it, then it feeds into something else.
Think of it as a production step that creates something with its own identity — its own materials, its own labor time, its own cost — even though the final customer only sees the end product.
What is a subassembly in manufacturing?
In manufacturing, a subassembly is any component that is assembled separately before being incorporated into a final product. Large manufacturers use subassemblies constantly — a car door handle is a subassembly; the door itself is a subassembly; both feed into the finished vehicle.
For small-batch makers, the same principle applies at a smaller scale. You’re still doing multi-step production. You’re still creating intermediate outputs. The question is just whether you’re tracking that structure — or letting it stay invisible.
Most makers who don’t use subassemblies end up with one very long flat recipe that mixes early-stage and late-stage materials together. This works up to a point. Then it gets messy: you can’t easily see the cost of each production step, you can’t reuse intermediate recipes across products, and troubleshooting a batch problem means tracing through a wall of ingredients.
Subassemblies fix that.
Examples of subassemblies for makers
Candle making — wax blend as a subassembly
If you make soy candles, you probably prepare your wax blend before pouring. Let’s say your process looks like this:
You melt soy wax, add fragrance oil and dye at a specific temperature, then pour into vessels (glass jar + wick already placed). The final product is a Vanilla Soy Candle in a glass jar.
But your wax blend — the soy wax + fragrance oil + dye, prepared at the right temperature and mixed thoroughly — is an intermediate product. You might make it in a large batch and then use it across several different candle sizes and vessels.
That wax blend is a subassembly. Its own BOM:
| Item | Type | Qty |
|---|---|---|
| Soy wax flakes | Material | 500g |
| Vanilla fragrance oil | Material | 50ml |
| Cream liquid dye | Material | 5ml |
And your finished candle BOM pulls that in:
| Item | Type | Qty |
|---|---|---|
| Vanilla Wax Blend (subassembly) | Component | 200g |
| Glass jar | Material | 1 |
| Pre-tabbed cotton wick | Component | 1 |
Note that the pre-tabbed wick is also a subassembly — if you’re cutting and tabbing your own wicks before use. That’s another production step with its own materials (cotton wick + metal wick tab) and labor.
Soap making — lye solution as a subassembly
If you make cold-process soap, you’re already doing multi-step production. Your lye solution — sodium hydroxide dissolved in distilled water — has to be made separately, allowed to cool, and then combined with your oils.
That lye solution is a textbook subassembly. It has its own materials, its own handling requirements, and its own production step that happens before you start on the actual soap batch.
Lye Solution (subassembly):
| Item | Type | Qty |
|---|---|---|
| Sodium hydroxide (lye) | Material | 60g |
| Distilled water | Material | 90ml |
Lavender Goat’s Milk Soap Bar (finished product):
| Item | Type | Qty |
|---|---|---|
| Lye Solution (subassembly) | Component | 150g |
| Goat’s milk | Material | 100ml |
| Olive oil | Material | 120g |
| Coconut oil | Material | 80g |
| Lavender essential oil | Material | 10ml |
| Lavender buds | Material | 5g |
| Soap mould | Material | 1 use |
By splitting it out, you can track exactly how much lye you’re using across all soap products, see the cost of that production step independently, and make the lye solution once per batch without re-entering the same two materials into every soap recipe.
Jewellery making — wire-wrapped component
If you make wire-wrapped earrings, you might prepare your wire coils or wrapped loops before assembling the finished piece. A wire-wrapped bead component — copper wire + semi-precious bead, assembled before the final pair is made — is a subassembly.
Same principle applies to any maker who does prep work that produces something distinct before the final assembly.
Subassembly vs. assembly — what’s the difference?
An assembly is the finished product — the complete, sellable unit. A subassembly is an intermediate product that gets incorporated into the assembly.
In a car: the engine is a subassembly. The car is the assembly. In candle making: the wax blend is a subassembly. The finished candle is the assembly. In soap making: the lye solution is a subassembly. The soap bar is the assembly.
Subassemblies can themselves contain sub-subassemblies. This is what “multi-level” means in a multi-level bill of materials — you can nest production steps inside other production steps, as many levels deep as your process requires.
Subassembly vs. component vs. material in Craftybase
New Craftybase users often ask how these three concepts map to what they see in the software. Here’s how it works:
| Term | What it is | Example |
|---|---|---|
| Material | A raw input purchased from a supplier | Lye, soy wax, fragrance oil, copper wire |
| Component | A product you make that becomes an ingredient in another product | Vanilla wax blend, lye solution, pre-tabbed wick |
| Subassembly | The concept — modelled in Craftybase as a Component with its own BOM | Any of the above |
Craftybase uses the word Component for what the broader manufacturing world calls a subassembly. When you create a product in Craftybase and give it its own bill of materials, that product can then be added as a component inside another product’s BOM. Craftybase automatically rolls up the cost from each component level through to the finished product — so your COGS calculation reflects every material and labor input, not just the top-level ones.
How to track subassemblies in Craftybase
Here’s the practical flow for setting up a subassembly in Craftybase:
- Create a new product for the subassembly (e.g. “Vanilla Wax Blend” or “Lye Solution”)
- Add a bill of materials to that product — list its raw materials and any labor time
- Create manufacture runs when you make a batch of the subassembly — this updates your stock of the subassembly and decrements your raw materials
- Open your finished product’s BOM and add the subassembly product as a component, with the quantity used per unit
From that point on, when you manufacture a batch of the finished product, Craftybase will:
- Decrement your subassembly stock (not the raw materials directly)
- Track the cost rolled up from the subassembly BOM
- Keep your COGS accurate at every level
This is particularly useful if you pre-batch your subassemblies in large quantities. You make 1kg of wax blend, enter that as a manufacture run, and then draw down from that stock across multiple candle production runs. No manual re-entry each time.
Learn more about Craftybase’s multi-level BOM software →
When should you use a subassembly?
Not every production step needs to become a formal subassembly. Here are the strongest indicators:
- You reuse the same intermediate product across multiple finished products. If your vanilla wax blend goes into three different candle sizes, model it once as a subassembly — not three times in each product’s flat BOM.
- The step involves significant separate labor. If pre-tabbing 200 wicks takes 45 minutes, you want that labor tracked independently, not buried in the candle BOM.
- You want to track usage of specific materials separately. Lye is a good example — it requires careful measurement and handling. Seeing your lye usage across all soap products in one place is genuinely useful.
- You produce the intermediate step in advance. If you make your wax blend or lye solution ahead of production runs (which most soap and candle makers do), it makes sense to treat it as manufactured inventory with its own stock level.
- You might outsource the step in future. If there’s any chance you’ll buy the intermediate product pre-made at some point, modelling it now as a subassembly makes that transition much easier.
Using software to manage subassemblies and multi-level BOMs
Spreadsheets can technically handle multi-level BOMs. But they get unwieldy fast — especially if you have multiple subassembly levels, multiple finished products drawing from the same subassembly, and real production runs you’re trying to track against them.
Purpose-built small business MRP software like Craftybase handles the nesting, cost roll-up, and inventory tracking automatically. When you record a manufacture run for a subassembly, stock updates. When you record a manufacture run for the finished product, it draws down from your subassembly stock. Your COGS at every level stays accurate.
Kasia from Rustic Maka uses Craftybase’s Components feature exactly this way for her natural body care products: she creates infusions as intermediate manufactured products (subassemblies) and then adds them as components into her finished product recipes. This means she only needs to enter the infusion recipe once — not in every product that uses it.
Frequently Asked Questions
What is a subassembly in manufacturing?
A subassembly is an intermediate manufactured product — assembled from raw materials or other components — that is then incorporated into a larger finished product. It is not something you buy (that's a raw material) and not something you sell directly (that's the finished product). In small-batch manufacturing, examples include a soap maker's lye solution, a candle maker's prepared wax blend, or a jewellery maker's wire-wrapped component. Each is made in a distinct production step before being used in the final item.
What is the difference between a subassembly and an assembly?
An assembly is the finished, sellable product — the complete unit your customer receives. A subassembly is an intermediate product that gets incorporated into the assembly before it is complete. In soap making, the lye solution is a subassembly; the finished soap bar is the assembly. In candle making, a prepared wax blend is a subassembly; the poured candle in its glass vessel is the assembly. Subassemblies have their own bills of materials and can be made and stocked independently of the finished product.
What is a subassembly on a bill of materials?
On a bill of materials, a subassembly appears as a line item in the parent product's BOM — but instead of being a raw material with a fixed purchase cost, it has its own nested BOM with its own materials and labor. This creates a multi-level structure: the finished product BOM references the subassembly, and the subassembly BOM lists what it's made from. Software that supports this structure can roll up costs through all levels automatically, giving you an accurate COGS figure for the finished product.
How do I track subassemblies in Craftybase?
Craftybase models subassemblies using its Components feature. Create a product record for the subassembly, add its own bill of materials (raw materials and labor), then record manufacture runs when you produce batches of it. Once you have subassembly stock on hand, add that product as a component in your finished product's BOM. Craftybase automatically rolls up costs from each component level — so your finished product COGS reflects every material and labor input, no manual calculation required. Makers who pre-batch intermediate products like infused oils, lye solutions, or wax blends find this saves significant re-entry time.
When should a handmade seller use subassemblies?
Subassemblies are worth setting up when an intermediate production step is reused across multiple products, involves significant separate labor, or uses materials you want to track independently. Common examples: infused carrier oils used across multiple skincare products, lye solutions in cold-process soap making, prepared wax blends in candle making, wire-wrapped components in jewellery. The clearest sign you need subassemblies is when you keep entering the same group of materials into multiple product BOMs — that's a strong signal the step should be modelled once and referenced everywhere.
