awesome-copilot/skills/powerbi-modeling/references/MEASURES-DAX.md

DAX Measures and Naming Conventions

Naming Conventions

General Rules

• Use human-readable names (spaces allowed)
• Be descriptive: Total Sales Amount not TSA
• Avoid abbreviations unless universally understood
• Use consistent capitalization (Title Case recommended)
• Avoid special characters except spaces

Table Naming

Type	Convention	Example
Dimension	Singular noun	Customer, Product, Date
Fact	Business process	Sales, Orders, Inventory
Bridge	Combined names	CustomerAccount, ProductCategory
Measure Table	Underscore prefix	_Measures, _KPIs

Column Naming

Type	Convention	Example
Keys	Suffix with "Key" or "ID"	CustomerKey, ProductID
Dates	Suffix with "Date"	OrderDate, ShipDate
Amounts	Descriptive with unit hint	SalesAmount, QuantitySold
Flags	Prefix with "Is" or "Has"	IsActive, HasDiscount

Measure Naming

Type	Convention	Example
Aggregations	Verb + Noun	Total Sales, Count of Orders
Ratios	X per Y or X Rate	Sales per Customer, Conversion Rate
Time Intelligence	Period + Metric	YTD Sales, PY Total Sales
Comparisons	Metric + vs + Baseline	Sales vs Budget, Growth vs PY

Explicit vs Implicit Measures

Always Create Explicit Measures For:

1. Key business metrics users will query
2. Complex calculations with filter manipulation
3. Measures used in MDX (Excel PivotTables)
4. Controlled aggregation (prevent sum of averages)

Implicit Measures (Column Aggregations)

• Acceptable for simple exploration
• Set correct SummarizeBy property:
  • Amounts: Sum
  • Keys/IDs: None (Do Not Summarize)
  • Rates/Prices: None or Average

Measure Patterns

Basic Aggregations

Total Sales = SUM(Sales[SalesAmount])
Order Count = COUNTROWS(Sales)
Average Order Value = DIVIDE([Total Sales], [Order Count])
Distinct Customers = DISTINCTCOUNT(Sales[CustomerKey])

Time Intelligence (Requires Date Table)

YTD Sales = TOTALYTD([Total Sales], 'Date'[Date])
MTD Sales = TOTALMTD([Total Sales], 'Date'[Date])
PY Sales = CALCULATE([Total Sales], SAMEPERIODLASTYEAR('Date'[Date]))
YoY Growth = DIVIDE([Total Sales] - [PY Sales], [PY Sales])

Percentage Calculations

Sales % of Total = 
DIVIDE(
    [Total Sales],
    CALCULATE([Total Sales], REMOVEFILTERS(Product))
)

Margin % = DIVIDE([Gross Profit], [Total Sales])

Running Totals

Running Total = 
CALCULATE(
    [Total Sales],
    FILTER(
        ALL('Date'),
        'Date'[Date] <= MAX('Date'[Date])
    )
)

Column References

Best Practice: Always Qualify Column Names

// GOOD - Fully qualified
Sales Amount = SUM(Sales[SalesAmount])

// BAD - Unqualified (can cause ambiguity)
Sales Amount = SUM([SalesAmount])

Measure References: Never Qualify

// GOOD - Unqualified measure
YTD Sales = TOTALYTD([Total Sales], 'Date'[Date])

// BAD - Qualified measure (breaks if home table changes)
YTD Sales = TOTALYTD(Sales[Total Sales], 'Date'[Date])

Documentation

Measure Descriptions

Always add descriptions explaining:

• What the measure calculates
• Business context/usage
• Any important assumptions

measure_operations(
  operation: "Update",
  definitions: [{
    name: "Total Sales",
    tableName: "Sales",
    description: "Sum of all completed sales transactions. Excludes returns and cancelled orders."
  }]
)

Format Strings

Data Type	Format String	Example Output
Currency	$#,##0.00	$1,234.56
Percentage	0.0%	12.3%
Whole Number	#,##0	1,234
Decimal	#,##0.00	1,234.56

Display Folders

Organize measures into logical groups:

measure_operations(
  operation: "Update",
  definitions: [{
    name: "YTD Sales",
    tableName: "_Measures",
    displayFolder: "Time Intelligence\\Year"
  }]
)

Common folder structure:

_Measures
├── Sales
│   ├── Total Sales
│   └── Average Sale
├── Time Intelligence
│   ├── Year
│   │   ├── YTD Sales
│   │   └── PY Sales
│   └── Month
│       └── MTD Sales
└── Ratios
    ├── Margin %
    └── Conversion Rate

Variables for Performance

Use variables to:

• Avoid recalculating the same expression
• Improve readability
• Enable debugging

Gross Margin % = 
VAR TotalSales = [Total Sales]
VAR TotalCost = [Total Cost]
VAR GrossProfit = TotalSales - TotalCost
RETURN
    DIVIDE(GrossProfit, TotalSales)

Validation Checklist

• All key business metrics have explicit measures
• Measures have clear, descriptive names
• Measures have descriptions
• Appropriate format strings applied
• Display folders organize related measures
• Column references are fully qualified
• Measure references are not qualified
• Variables used for complex calculations