Table of Contents

Provide Format String for Measures

  • 2026-01-09
  • Morten Lønskov

Overview

This best practice rule identifies visible measures with numeric or date data types that lack format strings. All measures should have explicit format strings for professional, consistent display.

  • Category: Formatting

  • Severity: Medium (2)

Applies To

  • Measures

Why This Matters

Measures without format strings display raw values, causing user confusion and inconsistent reporting. Format strings ensure:

  • Professional appearance: Values display with appropriate currency, percentage, or number formatting
  • Consistency: All reports show values in the same format
  • User confidence: Properly formatted numbers are easier to read and interpret
  • Business alignment: Formatting matches corporate standards

When This Rule Triggers

IsVisible
and string.IsNullOrWhitespace(FormatString)
and (DataType = "Int64" or DataType = "DateTime" or DataType = "Double" or DataType = "Decimal")

How to Fix

Manual Fix

  1. In TOM Explorer, select the measure
  2. In Properties pane, locate the Format String field
  3. Enter an appropriate format string based on what the measure calculates
  4. Save changes

Common Format Patterns

Total Revenue = 
SUM('Sales'[Amount])
// Format String: "$#,0"

Average Price = 
AVERAGE('Sales'[UnitPrice])
// Format String: "$#,0.00"

YoY Growth = 
DIVIDE([This Year] - [Last Year], [Last Year], 0)
// Format String: "0.0%"

Order Count = 
COUNTROWS('Orders')
// Format String: "#,0"

Common Causes

Cause 1: Missing Format Definition

When creating a new measure the defualt state is to not have any format string set.

Cause 2: Copy/Paste from Calculated Columns

Copying measures from columns that don't require format strings.

Example

Before Fix

Total Revenue = SUM('Sales'[Amount])
// No Format String

Display: 1234567.89 (hard to read, no currency symbol)

After Fix

Total Revenue = SUM('Sales'[Amount])
// Format String: "$#,0"

Display: $1,234,568 (clear, professional formatting)

Compatibility Level

This rule applies to models with compatibility level 1200 and higher.