When setting up Bills of Materials (BOMs) or tracking inventory in Luminous, it’s critical to understand how units of measure and unit classes work — especially when you're working with both bulk and small measurement units like gallons and ounces.
🔁 Can I Convert Between Ounces and Gallons?
Yes — but only if they belong to the same unit class.
Luminous supports unit conversions within the same class (like fluid volume or weight), but does not support cross-class conversions (like volume ↔ weight).
⚙️ How Unit Classes Work
A Unit Class defines the type of measurement — for example:
Quantity (each, dozen)
Weight (grams, pounds, kilograms)
Volume (ounces, gallons, liters)
Length (inches, feet, yards)
Each SKU is assigned a unit class, and only units within that class can be converted.
So:
✅ Ounces to Gallons (volume to volume) = Allowed
❌ Ounces to Pounds (volume to weight) = Not Allowed
🔧 Setting Up Conversion Rules (Within the Same Class)
To enable internal conversions, like from ounces to gallons:
Go to Inventory Admin > Units of Measure
Under the Conversion Rules tab:
Select your base unit (e.g., ounces)
Choose your target unit (e.g., gallons)
Set the conversion factor (e.g., 128 oz = 1 gallon)
These rules can be:
System-wide (applied across all products)
SKU-specific (helpful if different products have different densities or use-cases)
🧪 Example Use Case – Bike Lubricant
Sam asked:
“The bike lubricant is in 4 oz, can I put 4 and then oz or should I have everything in gallons?”
Here’s how we recommend approaching it:
If you purchase or receive it in 4 oz bottles but track and plan BOMs in gallons, set up a conversion rule:
Base Unit: Ounce
Target Unit: Gallon
Conversion: 128 oz = 1 gal
Now, in your BOM:
You can input
4 ozfor the componentLuminous will convert that into gallons during assembly or purchasing
This allows for cleaner tracking without forcing everything into a single unit
This keeps your numbers readable (no more 0.03125 gal per unit) and your data clean.
💡 Best Practices
Pick the right base unit: Go with the smallest common unit to avoid decimal complexity.
Use conversion rules where it makes sense: For example, convert grams to pounds for raw ingredients, or ounces to gallons for liquids.
Avoid mixing classes: If something is measured by weight (lbs), don’t try to convert it into a volume (gallons). If needed, you'll need to handle that outside of Luminous (e.g., via a density-based calculator or production SOP).
💬 Final Thoughts for BOM Setup
When building BOMs:
Stay within one unit class per raw material
Use conversions to switch between purchasing/selling units (e.g., buy in bulk, use in small quantities)
Keep units readable to make ongoing BOM updates easier for the team