Calculate the percent increase or decrease between two values, and the change needed to get back.
Enter the values to see the result here.
Formula
change %=∣old∣new−old×100
A positive result is an increase and a negative result is a decrease. The change needed to undo it solves (1+c)(1+u)=1:
u=1+c1−1
Worked example
A monthly subscription goes from 80 to 100.
Difference: 100−80=20.
Percentage change: 20/80×100=25% increase.
To go back to 80 the price must fall by 1/1.25−1=−20%.
The asymmetry is the point: a 25% rise needs only a 20% cut to reverse.
Common mistakes
Dividing by the new value instead of the old. 20 / 100 gives 20%, which is the share of the new price, not the increase.
Adding successive percentages. A 10% rise followed by another 10% rise is 21%, not 20%.
Confusing percentage points with percent. A rate change from 4% to 5% is 1 point, or 25%.
Computing a change from a base of zero.
Frequently asked questions
Why is a 50% drop followed by a 50% rise not back to the start?
The second percentage applies to a smaller base. 100 falls 50% to 50, and a 50% rise gives 75, not 100. You need a 100% rise to recover a 50% drop.
What if the old value is negative?
The tool divides by the size of the old value, so going from -10 to -5 is a 50% increase. That matches the direction of change on the number line, though accountants sometimes handle negative bases differently.
Why can't the old value be zero?
Any change from zero is infinite in percentage terms. Report the absolute difference instead.
Is percentage change the same as percentage points?
No. Moving an interest rate from 4% to 5% is a 1 percentage point rise but a 25% relative increase.