Running Total in Power Query M

Adds a running total column that accumulates a numeric column's values in row order.

Table TransformationsIntermediaterunning totalcumulativeindex

Power Query M code

let
    Source = YourTable,
    Indexed = Table.AddIndexColumn(Source, "Index", 0, 1, Int64.Type),
    AddedRunningTotal = Table.AddColumn(Indexed, "RunningTotal", each List.Sum(List.FirstN(Indexed[Amount], [Index] + 1)), type number)
in
    AddedRunningTotal

Notes

This re-sums everything up to each row (O(n^2) on large tables); for big datasets, calculate the running total as a DAX measure instead.

Requirements

A table already sorted in the order the running total should accumulate in.

How to use this snippet

In Power BI Desktop, choose Transform data to open Power Query, then open the Advanced Editor on a query (or start from a blank query).
Paste the snippet and replace the placeholder names (tables, columns, file paths) with your own. Check the requirements above first.
Run it through the Power Query M Formatter to tidy the layout.

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