This works out how much a figure has moved from one period to the next, as a percentage. The IFERROR keeps things clean when there is nothing to compare against.
The formula
=IFERROR((B2-A2)/A2,"") in column C
What each part does
(B2-A2)
How much it moved.
/A2
Divided by the starting value.
IFERROR(...,"")
Shows a blank instead of #DIV/0! when the starting value is zero.
How it works, and what to watch for
The change is the difference divided by the starting figure. Format the cell as a percentage rather than multiplying by a hundred, so the underlying number stays usable in later sums.
IFERROR steps in when the starting figure is zero, which would otherwise give a #DIV/0!. It leaves the cell blank instead.
A negative result means a fall. That is correct, not an error.
Questions
Should I multiply by 100?
No, let the cell formatting show the percentage. Multiplying by a hundred gives you a number you cannot easily use in a further calculation.
Why is my answer 0.27 rather than 27%?
The math is right; the cell just needs percentage formatting. Select it and press Ctrl+Shift+% and it will read as 27%.
Set by your computer's language, not by the file. A frequent cause of a correct-looking formula being rejected.
Excel version
XLOOKUP, IFS, TEXTBEFORE and TEXTJOIN need Microsoft 365 or 2021; older versions return #NAME? instead. Choosing the older one switches every walkthrough to a formula that works there.
