You cannot calculate a standard percentage increase from an original value of zero. The change exists, but the relative percentage is undefined.
Why the formula fails
For a value moving from 0 to 25, the percentage increase formula becomes:
((25 − 0) ÷ 0) × 100Division by zero is undefined. There is no finite percentage that turns zero into 25, because any percentage of zero remains zero.
This does not mean the value failed to grow. The absolute increase is 25. Only the percentage comparison lacks a valid baseline.
Do not label it as 100%
A rise from 0 to 25 is not a 100% increase. A 100% increase doubles the original value. Doubling zero still produces zero.
Software sometimes displays infinity or an error. “Undefined” is the clearest result for a general calculator.
Better ways to report the change
Depending on the situation, report:
- The absolute increase: “The count rose by 25.”
- The new value: “The count is now 25.”
- A later nonzero baseline: compare with the first period containing a meaningful value.
- A rate per person, visit, or unit when that denominator fits the question.
Do not choose a substitute baseline only to create an impressive percentage. The baseline should have a real meaning in the data.
What about values close to zero?
A very small positive baseline can produce an extremely large percentage. A move from 0.01 to 1 is a 9,900% increase. That is mathematically valid, but the absolute change of 0.99 may provide essential context.
Compare two values with a positive baseline
For spreadsheet handling, see the Excel guide or Google Sheets guide.