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Units of Measure

Audience: Business stakeholders, operations team, purchasing team

Overview​

Different items are measured in different ways. Some items are counted as individual pieces, others are weighed, and others are measured by volume. Our system supports flexible units of measure to handle real-world business scenarios.

What is a Unit of Measure?​

A unit of measure (UOM) is the standard way we quantify an item.

Examples​

  • Pieces: Bottle, Box, Pallet
  • Weight: Kilogram (kg), Gram (g), Pound (lb), Ton
  • Volume: Liter (L), Milliliter (mL), Gallon (gal), Fluid Ounce (fl oz)
  • Length: Meter (m), Centimeter (cm), Foot (ft), Inch (in)

Unit Classes​

Items don't specify a single fixed unit—they specify a unit class, which is a category of related units.

What is a Unit Class?​

A unit class is a group of units that measure the same thing and can be converted between each other.

Examples of Unit Classes​

Weight Class:

  • Kilogram (kg)
  • Gram (g)
  • Milligram (mg)
  • Pound (lb)
  • Ounce (oz)
  • Ton

Volume Class:

  • Liter (L)
  • Milliliter (mL)
  • Gallon (gal)
  • Fluid Ounce (fl oz)

Quantity/Count Class:

  • Piece (ea)
  • Dozen (doz)
  • Box
  • Case
  • Pallet

Length Class:

  • Meter (m)
  • Centimeter (cm)
  • Kilometer (km)
  • Foot (ft)
  • Inch (in)

Why Use Unit Classes Instead of Fixed Units?​

Flexibility​

Problem: Supplier sells fragrance oil in kilograms, but our production recipe requires grams.

Solution:

  • Item is set up with Weight unit class
  • Purchase order uses kilograms
  • Production uses grams
  • System automatically converts between them

Real-World Example​

Item: Lavender Fragrance Oil

  • Unit Class: Weight
  • Supplier: Sells in 5 kg bottles
  • Production Recipe: Requires 50 g per batch
  • Inventory Display: Warehouse manager prefers to see kilograms
  • All work together: System handles conversions automatically

Unit Conversions​

How Conversions Work​

The system knows how units within a class relate to each other.

Example: Weight Conversions​

  • 1 kilogram = 1,000 grams
  • 1 gram = 1,000 milligrams
  • 1 pound = 453.592 grams

Example: Volume Conversions​

  • 1 liter = 1,000 milliliters
  • 1 gallon = 3.78541 liters
  • 1 fluid ounce = 29.5735 milliliters

Example: Count Conversions​

  • 1 dozen = 12 pieces
  • 1 box = 24 pieces (if configured)
  • 1 case = 144 pieces (if configured)

Important: Count conversions (like box or case) are configurable per business because different companies may use different packaging standards.

Measurement Systems​

Metric System​

  • Used in most of the world
  • Based on units of 10
  • Examples: Kilogram, Liter, Meter

Imperial System​

  • Used primarily in the United States
  • Examples: Pound, Gallon, Foot

Why Support Both?​

  • International business: Suppliers in Europe use metric, US customers use imperial
  • User preference: Warehouse manager in London wants kilograms, manager in New York wants pounds
  • Regulatory requirements: Some countries require specific units on labels

See: Measurement Systems for more details.

How Items Use Units​

Item Setup​

When creating an item, you specify a default unit class:

Example:

  • Item: Rose Perfume Oil
  • Default Unit Class: Volume
  • Why: This is a liquid measured in liters or milliliters

Transaction Flexibility​

Even though the item has a default unit class, each transaction can specify which specific unit to use:

Purchase Receipt:

  • Received: 10 liters from supplier

Production Consumption:

  • Used: 500 milliliters in manufacturing

Inventory Display:

  • Current stock: 9.5 liters (or 9,500 milliliters—same thing!)

Real-World Scenarios​

Scenario 1: Perfume Bottles​

Item: Midnight Rose Perfume 100ml

Setup:

  • Default Unit Class: Count (Quantity)
  • Why: We count bottles as individual pieces

Transactions:

  • Purchase: +1,000 pieces from supplier
  • Sales: -50 pieces to customer
  • Current Inventory: 950 pieces

Note: Could also use "Case" if supplier ships in cases of 24 bottles each

Scenario 2: Fragrance Oil​

Item: Jasmine Fragrance Oil

Setup:

  • Default Unit Class: Volume
  • Why: It's a liquid

Transactions:

  • Purchase: +20 liters from supplier
  • Production: -250 milliliters per batch
  • Current Inventory: 19.75 liters (or 19,750 milliliters)

Benefit: Production recipe uses milliliters (easier to measure small amounts), but we purchase in liters (standard supplier packaging). System handles the conversion.

Scenario 3: Packaging Material​

Item: Cardboard Gift Boxes

Setup:

  • Default Unit Class: Count (Quantity)
  • Why: We count boxes as pieces

Transactions:

  • Purchase: +10 cases (1 case = 100 boxes = 1,000 boxes total)
  • Production: -50 boxes used
  • Current Inventory: 950 boxes (or 9.5 cases)

Unit Precision​

Different units have different precision requirements.

Examples​

Kilograms:

  • Precision: 2 decimal places
  • Example: 5.75 kg

Grams:

  • Precision: 1 decimal place
  • Example: 250.5 g

Pieces:

  • Precision: 0 decimal places (whole numbers only)
  • Example: 100 pieces (not 100.5 pieces—you can't have half a bottle!)

Milliliters:

  • Precision: 2 decimal places
  • Example: 150.25 mL

Why It Matters: The system enforces precision to prevent nonsensical quantities like "5.73482 bottles."

Base Units​

Each unit class has a base unit—the fundamental unit used for conversions.

Weight Class​

  • Base Unit: Gram (g)
  • All weight conversions calculated relative to grams
  • 1 kg = 1,000 g
  • 1 lb = 453.592 g

Volume Class​

  • Base Unit: Milliliter (mL)
  • All volume conversions calculated relative to milliliters
  • 1 L = 1,000 mL
  • 1 gal = 3,785.41 mL

Why Have a Base Unit?​

  • Simplifies conversion calculations
  • Ensures consistency
  • Reduces rounding errors

Example:

  • To convert 5 liters to gallons:
    1. Convert 5 L → 5,000 mL (to base unit)
    2. Convert 5,000 mL → 1.32 gal (from base unit)

Business Rules​

Rule 1: Transactions Must Use Compatible Units​

Valid:

  • Item with Volume class → transaction in liters ✓
  • Item with Volume class → transaction in milliliters ✓

Invalid:

  • Item with Volume class → transaction in kilograms ✗ (wrong class!)

Rule 2: Conversions Only Within Same Class​

You can convert:

  • Kilograms ↔ Grams (both Weight class)
  • Liters ↔ Milliliters (both Volume class)

You cannot convert:

  • Kilograms ↔ Liters (different classes—weight vs volume)
  • Pieces ↔ Kilograms (different classes—count vs weight)

Rule 3: Count Units Are Special​

Pieces, Boxes, Cases:

  • These are "countable" units
  • No inherent conversion factor (varies by item)
  • Conversions must be set up per business need

Example:

  • For Company A: 1 case = 24 pieces
  • For Company B: 1 case = 12 pieces
  • For Item X: 1 box = 10 pieces
  • For Item Y: 1 box = 6 pieces

Common Questions​

Q: Can I change an item's unit class after it's created?​

A: Generally no, especially if the item has existing inventory or transactions. Changing units would invalidate historical data.

Q: What if my supplier uses imperial units but I want metric?​

A: No problem! Set up the item with the appropriate unit class (e.g., Weight), then:

  • Purchase order uses pounds (imperial)
  • Inventory displays kilograms (metric)
  • System converts automatically

Q: Can I create custom units?​

A: Yes, within reason. You can add units to existing unit classes (e.g., add "Barrel" to the Volume class), but you must define the conversion factor to the base unit.

Q: What unit should I use for perfume bottles?​

A: Depends on your business:

  • Pieces: If you count individual bottles
  • Volume: If you focus on the liquid volume inside (50ml, 100ml)
  • Most companies use Pieces for finished bottles and Volume for bulk liquids

Best Practices​

Choose the Right Unit Class​

  • Liquids: Use Volume class
  • Solids (weighed): Use Weight class
  • Countable items: Use Count/Quantity class
  • Materials by length: Use Length class

Be Consistent​

  • Similar items should use the same unit class
  • Document your standards (e.g., "all perfume oils use Volume")
  • Train staff on which units to use when

Use Natural Units for Each Operation​

  • Purchasing: Use supplier's preferred unit (liters, pounds)
  • Production: Use recipe's natural unit (grams, milliliters)
  • Sales: Use customer's expected unit (bottles, pieces)
  • Let the system handle conversions

Avoid Unnecessary Precision​

  • Bottles: 0 decimals (whole numbers)
  • Kilograms: 2-3 decimals maximum
  • Milliliters: 1-2 decimals maximum
  • More precision = more data entry errors

Last Updated: 2025-10-28