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Custom column examples in Power Query

Learn practical Power Query Custom column examples with M code, UI steps, common mistakes, FAQs and copy-ready transformation patterns.

Updated 2026-06-125 practical examplesCopy-ready M code

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When to use this Power Query pattern

Use this pattern when the same data preparation step needs to happen every time a file, table or report refreshes.

Syntax or pattern

Table.AddColumn(Source, "Margin", each [Revenue] - [Cost], type number)

Typical UI steps

  1. Open Power Query Editor.
  2. Select the relevant column or query.
  3. Apply the transformation from the ribbon or formula bar.
  4. Review the generated step.
  5. Check data types and row counts before loading.
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5 practical examples

1

Use Custom column in a sales report

This example shows how to use Custom column when preparing a sales report.

Table.AddColumn(Source, "Margin", each [Revenue] - [Cost], type number)

Use this pattern when the sales report needs a repeatable transformation instead of manual cleanup.

2

Use Custom column in a customer list

This example shows how to use Custom column when preparing a customer list.

Table.AddColumn(CleanSource, "Margin", each [Revenue] - [Cost], type number)

Use this pattern when the customer list needs a repeatable transformation instead of manual cleanup.

3

Use Custom column in a inventory export

This example shows how to use Custom column when preparing a inventory export.

Table.AddColumn(Inventory, "Margin", each [Revenue] - [Cost], type number)

Use this pattern when the inventory export needs a repeatable transformation instead of manual cleanup.

4

Use Custom column in a monthly dashboard

This example shows how to use Custom column when preparing a monthly dashboard.

Table.AddColumn(ReportData, "Margin", each [Revenue] - [Cost], type number)

Use this pattern when the monthly dashboard needs a repeatable transformation instead of manual cleanup.

5

Use Custom column in a operations tracker

This example shows how to use Custom column when preparing a operations tracker.

Table.AddColumn(Tracker, "Margin", each [Revenue] - [Cost], type number)

Use this pattern when the operations tracker needs a repeatable transformation instead of manual cleanup.

Common mistakes to avoid

  • Applying steps in an order that makes later cleaning harder.
  • Forgetting that step names are referenced by later M code.
  • Not checking row counts before and after transformations.

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FAQ

When should I use Custom column in Power Query?

Use Custom column when the transformation should be repeatable every time the data refreshes.

Can I do Custom column from the Power Query interface?

Usually yes. The interface creates the M code for many common transformations, and you can adjust it in the formula bar or Advanced Editor.

Should I edit the M code manually?

Edit M manually when the interface cannot express the pattern clearly, or when you need reusable logic, parameters or cleaner step names.