Build assemblies,
track every component.

A Bill of Materials (BOM) defines an assembly -- the finished product you build from individual components in your inventory. Each BOM specifies which items go into the build and how many of each are needed.

To create a new BOM, navigate to the Bill of Materials section in the sidebar and click the + button, or press ⌘N on macOS.

• Select an output item from your inventory -- this is the finished product the assembly produces
• Set the output quantity to define how many units of the finished product one build produces (default is 1)
• Click Add Component to begin adding parts to the assembly
• For each component, search your inventory to select the item, then enter the quantity required per build
• Repeat until all components are listed, then save the BOM

On iPad, tap the + button in the top toolbar to create a new BOM. The form works identically -- tap a component row to adjust its quantity or remove it.

StringsTheory automatically calculates the total material cost of each assembly by summing up the unit cost of every component multiplied by its required quantity. This cost updates in real time as you add, remove, or adjust components.

• Each component row shows: item name, quantity needed, unit cost, and line total
• The total material cost appears at the bottom of the component list and updates instantly as you make changes
• If a component's unit cost changes in your inventory, the BOM cost reflects that change the next time you view it

StringsTheory is UOM-aware (Unit of Measure). When an inventory item uses a multi-unit package -- for example, a bag of 100 screws -- the cost calculation automatically divides the item's cost by its unitsPerPackage value to determine the true per-unit cost. This means you always see accurate material costs regardless of how your supplier packages items.

Beyond the standard fields (name, quantity, cost), you can define custom component fields that are tracked per serialized unit in a build. These are especially useful for recording specifications, tolerances, or batch information on individual components.

• Navigate to Settings and select Component Fields
• Click Add Field to create a new custom field
• Choose a field type: Text (free-form entry), Number (numeric values with optional decimal places), or Date (date picker)
• Give the field a descriptive name (e.g. "Wire Gauge", "Pot Value", "Capacitor Rating")
• Save -- the field will now appear on every component when editing a BOM or viewing serialized units

Component fields are especially powerful when combined with serialized production tracking. Each serialized unit in a build can have its own values for these fields, letting you record exactly which specific component specifications went into each finished product.

When you create a work order that involves building or assembling something, you can link a BOM directly to the order. This pulls in the full component list and material cost, giving you (and your customer) clear visibility into what the job requires.

• Open the Work Orders section and create a new work order (or edit an existing one)
• In the work order form, look for the Bill of Materials selector
• Choose the relevant BOM from the dropdown -- it lists all your saved assemblies
• Once linked, the work order detail view displays the full component breakdown with quantities and costs
• The total material cost from the BOM is incorporated into the work order's cost summary

This linkage means you can quote customers accurately before starting a job, because the material cost is calculated from your real inventory data, not estimates.

When you generate a PDF from a work order that has a linked BOM, the printed document includes a complete component breakdown. This gives your customers a transparent view of what goes into the build and what it costs.

• Open a work order with a linked BOM and click Print or Export PDF (⌘P on macOS)
• The PDF includes a Materials section listing each component, its quantity, unit cost, and line total
• A Total Material Cost line appears at the bottom of the component table
• Labor and other charges are listed separately, so the customer sees a clear breakdown of materials vs. service

This is particularly valuable for custom builds where the customer wants to understand exactly what they are paying for. A wiring harness build, for instance, would list every pot, switch, capacitor, wire run, and jack with individual costs and a total.