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:

  1. Go to Inventory Admin > Units of Measure
  2. 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 oz for the component
  • Luminous 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