Percentage Change Calculator
Calculate the percentage increase or decrease between two values, with the absolute difference.
The percentage change calculator tells you how much a value has grown or fallen in percentage terms. Use it for price changes, profit growth, weight loss, exam marks or any two numbers you want to compare.
How to use the calculator
- Enter the original value — the starting point.
- Enter the new value — the figure after the change.
- The calculator shows the percentage change and the raw difference.
- A positive result is an increase; a negative result is a decrease.
How it is calculated
Worked example
From 500 to 625
Difference = 125
Percentage change = 125 ÷ 500 × 100 = 25% increase.
Who should use this calculator
- Business owners comparing this month's sales, costs or profit with a previous period.
- Anyone checking how much a price, salary, rent or bill has moved, and by how much in absolute terms.
- Students interpreting changes in marks, attendance or measurements across two sets of numbers.
- People sanity-checking a growth claim, where "up 50%" usually means something more specific.
Common mistakes to avoid
- Using the new value as the base. Percentage change is always measured against the original figure. Dividing by the new number understates an increase and overstates a decrease.
- Dropping the minus sign. A fall of 12% is not the same as a rise of 12%, and in business reporting the direction is the whole point.
- Calculating change from zero. Percentage change from a base of zero is mathematically undefined. In that case only the absolute difference is meaningful.
- Confusing percentage change with percentage difference. Change has a direction and an original value; difference compares two values without a starting point, usually against their average.
- Comparing changes over different periods. A 10% rise over one month and a 10% rise over a year are not comparable until you put both on an annual footing.
The base you choose changes the story
From 500 to 625 is an increase of 125, which is 25% of the original 500. Reported the other way — 625 falling to 500 — the same move is a 20% decrease, because the base is now 625. Same numbers, same absolute change, two very different percentages.
This is not a trick; it is simply how percentages work, and it is why comparative reporting should always state the base. The effect becomes dramatic when values are far apart. A fall from 100 to 50 is a 50% drop, but recovering from 50 to 100 is a 100% rise. Whenever a percentage appears in a report or an advertisement, the useful question is always the same: percentage of what?
Percentage change terms explained
- Original value
- The starting figure. All percentage change is measured against it, so it defines the whole result.
- Absolute difference
- The plain subtraction between two values, with no reference to the base. It is the same whichever direction you calculate.
- Percentage increase
- A positive change: (new − old) ÷ old × 100.
- Percentage decrease
- A negative change, where the new value is smaller than the original.
- Annualised change
- A change restated as a yearly figure, which makes different time periods comparable.
- Base effect
- When a small base makes a change look dramatic. Rising from 20 to 30 is a 50% increase, even though the absolute change is only 10 units — which is why percentage figures should always be read alongside the numbers behind them.
Change across a series of periods
A single percentage change is easy. A chain of them is where people go wrong, because you cannot simply add the percentages. If sales rise 10% in one year and 10% the next, the total increase is 21%, not 20% — the second year starts from the higher base. Multiply the growth factors instead: 1.10 × 1.10 = 1.21. The same applies to inflation, to interest and to any figure quoted period after period, and it explains why a small annual change compounds into a surprisingly large one over a decade.
Frequently asked questions
How is percentage change different from percentage difference?
Percentage change compares a new value against an original one and has a direction (increase or decrease). Percentage difference compares two values without a starting point, and is usually expressed as a share of their average.
What if the original value is zero?
Percentage change from zero is undefined, because dividing by zero has no meaning. In that case only the absolute difference makes sense.
Can the result be more than 100%?
Yes. A change greater than 100% means the new value is more than double the original — for example, growing from 100 to 250 is a 150% increase.