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, on the Units & conversions page, in the Unit conversions section beneath the unit list.

Go to Settings → Units.
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.

You can also add one without leaving the page you are on: the restock grid’s More actions menu has Units and Conversions entries, and both the restock grid and the unit-change dialog offer to create the exact missing one inline.

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 material that isn’t used by any finished good or assembly bill, the change saves immediately — there are no quantities to keep consistent.

When the material is used, the Change unit of measure? dialog asks how to apply the change before saving. It lists each affected material with its unit change and the conversion it would use, 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.

Apply commits the choice. Converting a unit also recomputes the stored costs of every finished good and assembly bill that used the material, innermost first, so cost roll-ups stay correct after the change.

When no conversion exists

If you pick a new unit and no usable conversion exists for the old → new pair, Assemblified can’t safely convert. The dialog marks that row Needs a conversion, shows the warning There is no conversion for these units, and the only way forward is one of:

Add the conversion inline. A button reading Add kg to g (with your own two units in it) 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. Tick the materials on the list, then Material settings → Set unit in the bulk bar. The same dialog opens for the whole selection: it groups the affected materials and shows one Add … 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 recipe. Keep recipe quantities in the same unit as the 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 finished good or assembly bill 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 weight roll-up on a finished good or assembly bill, another consumer of these conversions.
Raw materials overview — back to the section root.