Unit conversions

A unit conversion is a stored factor between two units of measure — 1 kg = 1000 g, 1 m = 100 cm. On its own a conversion changes nothing about how a recipe runs. Its job is to let Assemblified do the arithmetic for you the moment a unit genuinely changes, so a physical requirement is preserved rather than mislabelled.

The headline use is changing a referenced material’s unit. Without conversions, switching a material from cm to m would relabel 250 cm as 250 m — a 100× error that every downstream pick list, shortage list, and work order inherits. With a conversion in place, Assemblified rewrites 250 cm as 2.5 m instead.

Managing conversions

Conversions live under Settings → Units of Measurement, in the Unit Conversions section beneath the unit list.

Go to Settings → Units of Measurement.
Scroll to Unit Conversions and click Add conversion.
Pick the from unit, the to unit, and the factor (1 from = factor × to). For g → kg the factor is 0.001.
Save. The conversion is now available everywhere a conversion is needed.

Conversions are defined in one direction but usable in both — Assemblified inverts the factor automatically, so a single g → kg row also answers kg → g. You don’t need to enter the reverse.

Linear conversions only

Internally a conversion is an affine map (value_to = value_from × factor + offset). But quantity and cost propagation can only use linear conversions — ones where offset = 0, factor > 0, and the factor is finite. A per-unit quantity or cost has no meaningful zero-point shift, so an offset (the kind a °C → °F conversion would need) is never applied to recipe math.

In practice every multiplicative conversion you’d define for materials — weight, length, volume, count — is linear and works. The restriction only excludes offset-based temperature-style conversions, which don’t belong on a recipe quantity anyway.

Changing a referenced material’s unit

When you change the unit on a raw material that isn’t referenced by any BOM or sub-assembly, the change saves immediately — there are no quantities to keep consistent.

When the material is referenced, Assemblified pauses and asks how to apply the change before saving. The dialog summarises each affected material (old → new, recipe count) and offers:

Choice	What it does	Default
Convert recipe quantities	Every recipe quantity is recalculated by the conversion factor — `250 cm` becomes `2.5 m`, the physical requirement is preserved.	On
Convert unit cost	Recalculates the per-unit cost for the new unit so total cost (`quantity × cost`) stays put. Only offered for materials whose cost you can edit — not Shopify-linked materials, whose cost is owned by Shopify.	Off
Change unit only	The display-only escape hatch: relabels the unit without touching any number.	—

The math, for cm → m (factor 0.01):

Quantity — new = old × factor, so the amount consumed is unchanged.
Unit cost (opt-in) — new = old ÷ factor, so the total cost is unchanged.

Converting a unit also recomputes the cached BOM and sub-assembly costs that referenced the material, leaf-first up the sub-assembly graph, so cost roll-ups stay correct after the change.

When no conversion exists

If you pick a new unit and no linear conversion exists for the old → new pair, Assemblified can’t safely convert. The dialog flags the pair as Needs conversion and blocks the convert path. From there you can:

Add the conversion inline. An Add from → to button opens the conversion editor locked to exactly that pair. Save it and the dialog re-checks — the convert path unlocks immediately, no need to leave and come back.
Change unit only. Fall back to the display-only relabel, accepting that you’ll fix the numbers yourself.

Bulk and import behavior

Bulk edit. Changing the unit on several materials at once funnels through the same dialog. It groups the affected materials and shows one Add from → to button per distinct unit pair, so you resolve each missing conversion once rather than per material.
Import / non-interactive changes. When a unit change arrives without a dialog choice — a CSV/XLSX import, or any non-interactive path — Assemblified applies convert-else-fail: it auto-converts every referenced material that has a usable conversion, and if any referenced material lacks one, it rejects the whole change with no partial writes. A non-interactive path never silently relabels.

Common gotchas

Conversions don’t apply at execution time. They fire only when a referenced material’s unit changes. A quantity you type into a recipe is always taken at face value in the material’s current unit — there’s no live conversion while you build a BOM. Keep recipe quantities in the same unit as the raw material. See Units → where the symbol shows up.
One direction is enough. Define g → kg or kg → g, not both — the inverse is automatic. Defining both is harmless but redundant.
Offsets are ignored for recipe math. A conversion with a non-zero offset is treated as “no usable conversion” for unit changes, so the convert path stays blocked. This only affects offset-style (temperature) conversions.
Weight roll-ups use these too. The calculated weight on a BOM or sub-assembly converts mixed component weight units into one canonical unit using these same conversions. The five seeded weight units (kg/g/mg/lb/oz) all convert to kg out of the box; a custom weight unit needs a conversion before it can roll up.

Where to next

Units of Measurement — the unit field itself, the built-in list, and adding custom units.
Weight — the calculated BOM / sub-assembly weight roll-up, another consumer of these conversions.
Raw materials overview — back to the section root.