More registrations
An event grows from 80 registrations to 100. The increase is 20 registrations, and 20 ÷ 80 × 100 gives a 25% increase.
Compare before and after
Results
Increase
25%
Absolute difference (new − old)
20
Ending / starting multiplier
1.25×
(100 − 80) ÷ 80 × 100
Reverse change, ending back to starting
-20%
The starting value must be positive. A negative ending value is allowed and can produce a decrease beyond 100%. Reverse percentages with a negative base are algebraic.
Calculations and exports run locally in your browser. Your entries are not sent to a calculation service.
How to use the Percentage Change Calculator
- 01
Enter a starting value greater than zero and an ending value in the same units.
- 02
Read the percentage alongside the absolute difference and ending-to-starting multiplier.
- 03
Swap values to examine the reverse direction, or download the comparison as text.
Examples
A reduction
A file shrinks from 250 MB to 175 MB. Its difference is −75 MB, percentage change is −30%, and ending multiplier is 0.7.
Returning to the starting point
Moving from 100 back to 80 is −20%. The original change from 80 to 100 was +25%, because the denominator was smaller.
The starting point determines the rate
The formula is (ending − starting) ÷ starting × 100. Choose the period or baseline deliberately. Reversing the order preserves the difference in magnitude but changes the denominator and usually changes the percentage magnitude.
Compare quantities with matching units
Use like-for-like measurements. If one file size is in megabytes and the other in gigabytes, convert them first. A percentage change between rates is also different from a percentage-point change: moving from 20% to 25% is 5 percentage points and a relative increase of 25%.
Negative endings and zero
This tool requires a positive starting baseline so the ordinary increase/decrease interpretation remains clear. It allows an ending value below zero; the resulting decrease can exceed 100%. An ending value of zero gives −100%, while its reverse percentage is undefined.
What to know
- Starting value must be strictly positive.
- Decimals are truncated after 12 places. Negative-base reverse results are algebraic and may not describe ordinary growth.
Common questions
What does the multiplier mean?
It is ending divided by starting. A factor of 1.25 means the ending value is 125% of the starting value. A factor of 0.7 means 70% remains.
Why can I not start from zero?
The standard relative-change formula divides by the starting value. A transition from zero to a positive amount has an absolute difference but no finite percentage increase under this formula.
Is this symmetric percentage difference?
No. Symmetric percentage difference commonly divides by an average of the two values. This tool intentionally uses the starting value as its baseline.