Percentage Change Calculator
Calculate the percentage increase or decrease between two values, and the percentage difference when neither value is the reference point.
How to use this calculator
- 1Enter the original value and the new value.
- 2A positive result is an increase, a negative one a decrease.
- 3Use the "percentage difference" figure when comparing two measurements where neither came first.
How the calculation works
Change % = (New − Old) / |Old| × 100 Difference % = |New − Old| / ((|Old| + |New|)/2) × 100- Old
- The original or reference value
- New
- The value being compared
Percentage change is directional — it needs a "before". Percentage difference is symmetric and treats both values equally.
Change from zero is undefined, because dividing by zero has no meaning. Report the absolute change instead.
Worked example
From 50 to 65
- 1.The change is 65 − 50 = 15.
- 2.Divide by the original: 15 ÷ 50 = 0.3.
- 3.Multiply by 100: a 30% increase.
Result: +30%
What percentage change actually measures
Percentage change describes how much a value has moved, scaled against where it started. A price that goes from $50 to $65 has risen by $15 in absolute terms, but reporting it as "+30%" is usually more useful, because it says something about the size of the move relative to the starting point — the same $15 rise would be a much bigger deal on a $20 item than on a $2,000 one.
That relativity is also why the starting value matters so much: the same absolute change can produce very different percentage changes depending on what it started from, and the same percentage change can represent very different absolute amounts.
Why going up and coming back down are not symmetric
One of the more counter-intuitive facts about percentages is that a rise and a fall of the same size do not cancel out. If a value drops 50%, it takes a 100% rise — not another 50% — to get back to where it started, because the second percentage is calculated on a smaller number.
This shows up constantly with investment losses: a portfolio that falls 50% needs to double, not just recover 50%, before it is back to even. The steeper the drop, the more disproportionate the recovery needed to undo it.
Percentage change vs percentage difference
These two terms sound interchangeable but answer different questions. Percentage change assumes there is a clear "before" and "after" and divides the change by the original value — it is directional, and swapping the two numbers flips the sign. Percentage difference makes no such assumption: it divides by the average of the two values instead, so it gives the same answer regardless of which number is considered first.
Use percentage change for anything with a genuine timeline — last year’s revenue versus this year’s, or a price before and after a sale. Use percentage difference when comparing two independent measurements where neither one is obviously "the original," such as two competing quotes or two lab readings.
Where percentage change shows up
This calculation sits behind a lot of the numbers people see in the news and in their own finances.
- Investment returns — the percentage gain or loss on a stock, fund or portfolio over a given period.
- Inflation and prices — the Consumer Price Index and everyday price comparisons are both expressed as a percentage change over time.
- Salaries and raises — a pay rise is usually quoted as a percentage of the previous salary, not a flat dollar figure.
- Population and growth statistics — city, company and user-base growth rates are almost always reported as year-over-year percentage change.
A common mistake worth avoiding
It is tempting to treat two percentage changes as if they simply add together — assuming a 10% increase followed by a 15% increase gives a 25% total increase. They do not, because the second percentage is applied to the already-increased value, not the original one. Two successive percentage changes compound rather than add: a 10% rise followed by a 15% rise actually works out to a 26.5% overall increase.
What this assumes, and where it stops
Assumptions
- The original value is the reference point for percentage change.
Limitations
- Undefined when the original value is zero.
- With negative values, percentage change can behave counter-intuitively; this calculator divides by the absolute value of the original so the sign of the result reflects the direction of movement.
Common questions
What is the difference between percentage change and percentage difference?
Percentage change assumes one value came first and divides by it. Percentage difference makes no such assumption and divides by the average of the two, so you get the same answer whichever order you enter them. Use change for before-and-after; use difference for comparing two independent measurements.
Can percentage change be more than 100%?
Yes, for increases — a value that triples has risen 200%. Decreases cannot exceed 100% unless the new value is negative, because you cannot lose more than everything.
Formula and content last reviewed on .
Results are estimates for information only, not professional advice.
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