Percentage Change Calculator

Frequently asked questions

What is the percentage change formula?

Subtract the old value from the new value, divide by the absolute value of the old value, then multiply by 100. A positive result is an increase and a negative result is a decrease. For example, from 80 to 100 is a 25% increase.

What happens when the old value is zero?

Percentage change is mathematically undefined when the starting value is zero, because you would be dividing by zero. The calculator displays "Undefined" in that case. If your old value genuinely is zero, consider using the absolute change figure instead.

How is percentage change different from percentage points?

Percentage change measures how much a value grew or shrank relative to its original size. Percentage points measure the arithmetic difference between two percentages. If an interest rate rises from 2% to 3%, that is 1 percentage point but a 50% percentage change.

Can I use this for negative numbers?

Yes. The formula works for any non-zero starting value, including negatives. The calculator uses the absolute value of the old number in the denominator, which is the standard convention and ensures a drop from -50 to -100 is shown as a 100% increase in magnitude.