Using conditional formatting to highlight cells that dont add up to 100%

[nickmax1]

I have rows M2:R999 that have varying percentage splits, but i want a simple colour check to tell me if i made a mistake and those cells DONT add up to 100%

I have tried =sum(M2:R2)<>100% but that doesnt seem to do anything...?

In my example spreadsheet I am expecting only M5 to R5 to be formatted in red, as it does not add up to 100%

 

[Fluff]

Hi & welcome to MrExcel.
You need to anchor the columns like

=sum($M2:$R2)<>100%

 

[nickmax1]

very strange, something different happens but not as expected....see image. Why would those rows get highlighted and not the row I am expecting?!?

 

[Joe4]

Because your formula needs to match the range you are applying it to.
Notice how the range you are applying it to starts on row 1, but the formula you entered references row 2.
These MUST match (otherwise the highlightlighting will be shifted and off rows, as you are seeing).
Always write the formula as it applies to the very first cell in your applied to range. Excel will adjust it for all other rows.