How to use this calculator
Enter a positive starting value and the new value. The starting value is the reference, so divide the difference by that value. Positive results mean an increase; negative results mean a decrease. The multiplier tells you what to multiply the starting number by to obtain the new number.
Formula
(New value − Starting value) ÷ Starting value × 100
Worked example
From 80 to 100: the change is +20, so 20 ÷ 80 × 100 = +25%, with multiplier 1.25. Going from 100 back to 80 is −20%, not −25%.
Assumptions and limitations
A starting value of zero gives no defined relative percentage change. Negative starting values are excluded because conventions differ. A negative new value is allowed and can produce a decrease greater than 100%. This is not a percentage-point calculator.
Frequently asked questions
What is the difference between percent and percentage points?
A rate rising from 20% to 25% increases by 5 percentage points. Relative to 20%, the increase is 5 ÷ 20 × 100 = 25%. Enter 20 and 25 here to get that relative change.
How precise are these results?
Calculations use ordinary floating-point arithmetic. Results show up to six decimal places; very small nonzero values use scientific notation. They are estimates for everyday arithmetic, not arbitrary-precision accounting.
Can I use decimals and negative numbers?
Yes where the input allows them. Percentage change requires a nonnegative starting value; difference uses nonnegative values; discount requires a nonnegative price and a rate between 0% and 100%.
Keep the same units for both values. Amounts have no assumed currency.