Guide · Change over time
Percentage Change Calculator
Updated: June 2026
Percentage change is the single number that captures how much something grew or shrank between two points in time. Unlike a plain increase or decrease, it carries a sign: positive for growth, negative for decline. That one figure is the backbone of every dashboard, financial report and trend line, which makes getting the formula — and the reference point — right surprisingly important.
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The percentage change formula
For an old (starting) value and a new (ending) value:
The result is signed. A positive answer is an increase, a negative answer a decrease, and zero means no change. Dividing by the absolute value of the old number keeps the sign of the change meaningful even when the starting value is negative — a detail that matters for things like temperatures or account balances.
Worked examples, both directions
Traffic rises from 1,200 to 1,500 visits: (1,500 − 1,200) ÷ 1,200 × 100 = +25%. Revenue falls from 50,000 to 42,000: (42,000 − 50,000) ÷ 50,000 × 100 = −16%. The same formula handles both; only the sign of the numerator changes. Reading the sign is how you turn raw numbers into a one-word verdict — up or down.
The reference point trap
The most common error is dividing by the wrong value. Percentage change is always relative to the starting figure, not the ending one. Going from 200 to 250 is a 25% increase (50 ÷ 200), but going back from 250 to 200 is a 20% decrease (50 ÷ 250). The absolute change is identical — 50 — yet the percentages differ because the base differs. Whenever you compare two periods, fix in your mind which one is "before".
| From | To | Change |
|---|---|---|
| 200 | 250 | +25% |
| 250 | 200 | −20% |
| 100 | 300 | +200% |
| 300 | 100 | −66.67% |
Percentage points vs percent
One more distinction worth keeping straight. If an interest rate moves from 4% to 6%, that is a rise of two percentage points, but a 50% increase in the rate itself (2 ÷ 4 × 100). News reports often blur the two; the calculator measures the latter — the percentage change of the underlying number — so be explicit about which you mean when you quote it.
Where you'll use it
- Quarter-over-quarter or year-over-year comparisons in reports.
- Tracking metrics on a dashboard where direction matters as much as size.
- Comparing before-and-after readings in experiments or A/B tests.
- Summarising any pair of measurements as a single signed figure.
Frequently asked questions
What is the percentage change formula?
Subtract the old value from the new, divide by the absolute value of the old, then multiply by 100. Positive is an increase, negative a decrease.
What does a negative percentage change mean?
The value went down. A change of −15% means the new figure is 15% smaller than the old one.
How is percentage change different from percentage difference?
Change has a before and after and divides by the starting value; difference compares two values with no order and divides by their average.
What's the difference between percent and percentage points?
A move from 4% to 6% is 2 percentage points, but a 50% increase in the rate. Change measures the latter.