Free tool Percentage increase and percentage change calculator
Enter an old value and a new value to get the percentage change, the absolute difference and the new value as a share of the old. Works for revenue, traffic, prices and rates — including negative numbers.
- Increase or decrease
- Negative values allowed
- Runs locally
Work out the change between two values
Put the earlier or reference value in “Old value”. Swapping the two gives a different percentage, because the change is measured against the old value.
The starting or reference value. Can be negative; cannot be 0 for a percentage.
The value you are comparing with it. Can be negative.
Percentage change
+28.0%
(New − old) ÷ |old|.
Share these inputs: the values go after the # in the link, so they never reach a server.
https://tapcub.com/tools/percentage-change-calculator
Version v1.0Updated Update history
Three ways to describe one change
The same movement can be reported as a percentage, a difference or a ratio. Pick the one your reader needs, and say which.
Percentage change
How big the change is relative to where you started. 1,250 to 1,600 is +28.0%. A plus sign means up, a minus sign means down.
Absolute difference
The change in the original units: +350 visits, −$2,000. Use it alongside the percentage when the base is small, where a few units make a large percentage.
New as % of old
The new value expressed as a share of the old: 128% means 1.28 times as large. Also the quick way to answer “what percent of A is B?”
Percent vs percentage points
When the values are themselves rates, a move from 2.0% to 2.5% is +0.5 percentage points but +25% in relative terms. Say which one you mean.
The direction matters: 100 to 125 is +25%, but 125 to 100 is −20%. The base is always the old value.
Three common uses
The same calculation covers most “how much did it change?” questions in a report.
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1
Period over period
Last month in “Old value”, this month in “New value” for month-over-month; the same month last year for year-over-year.
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2
Before and after
The metric before a release, price change or campaign as old, after it as new.
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3
Share of a total
Put the total in “Old value” and the part in “New value”; the “New value as % of old” line gives the share.
Percentage change = (new − old) ÷ |old| × 100%
Subtract the old value from the new one and divide by the size of the old value. Using the absolute value of the old value keeps the sign meaningful when the old value is negative: a loss shrinking toward profit shows as an increase.
- Positive result: increase. Negative result: decrease
- Percentage decrease = (old − new) ÷ old, the same number without the minus sign
- The old value cannot be 0: there is nothing to divide by
- For rates, report percentage points (new − old) as well as the relative change
Percentage change
change = (new − old) ÷ |old|
(1,600 − 1,250) ÷ 1,250 = +28.0%
Absolute difference
difference = new − old
1,600 − 1,250 = +350
Negative starting value
change = (new − old) ÷ |old|
(100 − (−200)) ÷ 200 = +150.0%
One monthly report, four kinds of change
Four lines from a month-over-month report. Each needs a slightly different reading.
| Metric | Last month | This month | Difference | Percentage change |
|---|---|---|---|---|
| Revenue | $1,250 | $1,600 | +$350 | +28.0% |
| Conversion rate | 2.0% | 2.5% | +0.5 pp | +25.0% |
| Bounce rate | 48% | 42% | −6 pp | −12.5% |
| Net profit | −$200 | $100 | +$300 | +150.0% |
For conversion and bounce rate, the difference column is in percentage points (pp) and the last column is the relative change. For net profit the base is negative, so the change is measured against its size, 200. Sample figures.
Where percentage changes go wrong
One subtraction and one division, and still a common source of wrong headlines.
Points vs percent
A rate going from 2% to 3% is up 1 percentage point and up 50%. Writing “up 1%” is wrong either way.
Swapping the base
Up from 100 to 125 is +25%; down from 125 to 100 is −20%. Always divide by the earlier value.
Undoing with the same percent
A 50% rise then a 50% fall leaves you at 75% of the start. Gains and losses of the same percentage do not cancel.
Tiny bases
Going from 2 sign-ups to 6 is +200%. With small numbers, lead with the absolute difference.
Period comparisons without the spreadsheet
In a report, the old and new values come from the same definition and the same filters. TapCub computes them from your events, so the change you read is the change in behaviour, not in how it was counted.
Percentage change questions
Still have a question?
Chat with the team behind TapCub — we usually reply within a few hours on business days.
How do I calculate percentage change? What is the formula?
Percentage change = (new − old) ÷ |old| × 100. Subtract the old value from the new value, divide by the old value and multiply by 100. From 1,250 to 1,600: (1,600 − 1,250) ÷ 1,250 × 100 = +28%, a 28% increase.
Is there a different formula for percentage decrease?
No. The same formula gives a negative number for a decrease. If you want a positive figure, percentage decrease = (old − new) ÷ old × 100: from 48 to 42 is a 12.5% decrease.
What is the difference between percent and percentage points?
Percentage points are the plain difference between two percentages; percent is the relative change. A conversion rate going from 2.0% to 2.5% is +0.5 percentage points and +25%.
How do I calculate percentage change with negative numbers?
Divide by the absolute value of the old number. From −200 to 100 is (100 − (−200)) ÷ 200 = +150%. Some analysts consider percentages across zero misleading, so show the absolute difference too.
What if the old value is zero?
Percentage change cannot be calculated, because you cannot divide by zero. Report the absolute difference instead, for example “from 0 to 40 sign-ups”.
Why does a 50% increase followed by a 50% decrease not get back to the start?
Because the second change is measured from a larger base. 100 up 50% is 150; 150 down 50% is 75. To undo a 50% rise you need a 33.3% fall.
What is the difference between percentage change and percentage difference?
Percentage change has a direction and uses the old value as the base. Percentage difference compares two values with no before and after, dividing by their average: |a − b| ÷ ((a + b) ÷ 2). This calculator gives percentage change.
Update history
New features, fixes and data refreshes for this tool, newest first.
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· v1.0
LaunchedFirst release.
Missing something or found an error? Tell us — requests that come up often go into the next update. All tool updates
From one change to a growth rate
A single change compares two points. For several periods, use a compound growth rate.