How to Create Custom Formulas in Looker Studio

Creating custom formulas in Looker Studio is a powerful way to transform and manipulate your data directly within the platform. Custom formulas allow you to perform calculations, apply conditions, create new metrics, and even derive insights that aren't readily available in your data source. From my experience, using custom formulas can enhance your reporting by allowing you to generate metrics that fit your specific analysis needs.

Here’s a step-by-step guide on how to create custom formulas in Looker Studio:

Step-by-Step Guide to Creating Custom Formulas

1. Open Your Report and Access the Data Panel

  • Start by opening the report where you want to add the custom formula.
  • Make sure you’ve connected a data source to the report, as custom formulas will rely on fields from that source.
  • In the Data Panel on the right side, you will see the fields from your data source.

2. Add a New Field for the Formula

  • In the Data Panel, scroll down and click the + Add a Field button at the bottom of the available fields list.
  • This will open the Create Field window where you can define your custom formula.

3. Name the Formula Field

  • At the top of the Create Field window, give your custom formula a descriptive name. This will be the name that appears in your report.
  • For example, if you're calculating profit margin, you might name the field "Profit Margin."

4. Write the Custom Formula

  • In the Formula box, you will enter the custom formula.
  • Looker Studio provides a wide range of functions that allow you to create mathematical, logical, string, and date-related formulas.
Common Formula Types:

  • Basic Arithmetic: You can perform basic math operations like addition, subtraction, multiplication, and division.

    Profit = Revenue - Cost

  • String Manipulation: Use string functions like CONCAT() to combine fields or LOWER() to transform text.

    Full Name = CONCAT(FirstName, " ", LastName)

  • Date Functions: Perform calculations with date fields, such as finding the difference between dates.

    Days Since Purchase = DATE_DIFF(TODAY(), PurchaseDate)

  • Conditional Logic (CASE): Use the CASE function to apply logic based on conditions.

    CASE
      WHEN Sales > 1000 THEN "High"
      ELSE "Low"
    END

  • Aggregations: You can also use aggregate functions like SUM(), AVG(), or COUNT() to summarize data.

    Total Revenue = SUM(Revenue)
Example Custom Formula:

If you wanted to calculate Profit Margin using revenue and cost, you would write the following formula:

Profit Margin = (Revenue - Cost) / Revenue

5. Use Built-in Functions

  • Looker Studio offers several built-in functions to create custom formulas. As you start typing, Looker Studio will suggest available fields and functions that match your input. Some useful functions include:
    • Mathematical Functions: SUM(), AVG(), MIN(), MAX()
    • String Functions: CONCAT(), LOWER(), UPPER()
    • Date Functions: DATE_DIFF(), TODAY(), YEAR()
    • Logical Functions: IF(), CASE(), AND(), OR()

You can find a full list of supported functions in Looker Studio's documentation, or by browsing through the functions available in the formula editor.

6. Validate the Formula

  • After writing your custom formula, click Validate to check for any errors.
  • Looker Studio will highlight any syntax errors or issues with your formula. For example, if you reference a field that doesn’t exist or use an invalid function, it will notify you.

7. Save the Formula

  • Once the formula is validated, click Save to add it as a new field in your data source.
  • The new custom field will now appear in the Available Fields section of the Data Panel.

8. Use the Custom Formula in Your Visualizations

  • You can now use the custom formula field just like any other field in your report.
  • Drag and drop the formula field into charts, tables, or scorecards to display the results.
  • For example, if you created a "Profit Margin" field, you could drag it into a table to show the calculated margin for each row of data.

Example: Common Use Cases for Custom Formulas

  1. Revenue per User:

    Revenue Per User = Revenue / Users

  2. Conversion Rate:

    Conversion Rate = (Conversions / Sessions) * 100

  3. Average Order Value:

    Average Order Value = Revenue / Orders

  4. Customer Lifetime Value:

    CLV = AVG(Revenue) * (1 / Churn Rate)

  5. Total Cost of Goods Sold:

    Total COGS = SUM(Cost * Quantity Sold)

  6. Text Concatenation for Full Names:

    Full Name = CONCAT(FirstName, " ", LastName)

Tips for Using Custom Formulas in Looker Studio

  • Keep It Simple: Avoid overly complex formulas where possible. If you need multiple calculations, consider breaking them into smaller steps with individual formula fields.
  • Use Descriptive Field Names: Name your custom fields clearly so that anyone viewing the report will understand what the field represents.
  • Test the Formula: After creating a custom formula, test it in different visualizations to ensure it works correctly with your data.
  • Optimize for Performance: If you're working with large datasets, try to keep your formulas efficient. Complex calculations can slow down report performance. Pre-processing data in the source (e.g., in Google Sheets or BigQuery) can help reduce the complexity in Looker Studio.

Conclusion

Custom formulas in Looker Studio provide a flexible way to tailor your data analysis and reporting. By creating new metrics, performing calculations, and applying logic to your data, you can gain deeper insights and create more meaningful visualizations. Whether you're calculating profit margins, analyzing user behavior, or manipulating text fields, custom formulas give you the power to extend the capabilities of Looker Studio to meet your reporting needs.

For more insights on customizing your reports, explore How to Add a Formula Field in Looker Studio or How to Use Calculated Fields in Looker Studio.

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