Percentage Calculator
Work out a percentage change and get the Excel formula that does the same thing on your own data.
When to use this
- Working out growth between two periods
- Checking a discount, margin or achievement against target
- Recovering an original price from a total that already includes a change
How the formula works
Taking the example on this page apart, piece by piece:
=(B2-A2)/A2
(B2-A2)The change: the new value in B2 minus the original in A2.
/A2Divided by the original value, which turns the change into a fraction of where it started. Format the cell as a percentage to show it as one.
Where it goes wrong
Multiplying by 100 and formatting as a percentage
Excel's percentage format already multiplies by 100 for display. Doing both gives 3000% where you wanted 30%.
Confusing percentage change with percentage difference
Change is measured against where you started, so it is not symmetric. Difference is measured against the average of the two, so it reads the same either way round.
Adding percentages together
A 10% rise followed by a 10% fall does not get you back to where you started. Apply them one after another rather than summing them.
Practise it
A generator gives you the formula. These give you the reason it works — and tell you which assumption broke when it does not.
- Calculate achievement against target · beginner