Change Percentage Calculator
Change from A to B
Enter your old and new value to instantly see how much it's increased or decreased — as a percentage, with the full calculation shown so you can verify it yourself.
What is a percentage change? – Explained simply
A percentage change tells you how much something has grown or shrunk compared to where it started, expressed as a percentage, always measured against the old value. People run into this same question in all kinds of situations — comparing two prices, working out a salary increase, tracking a weight change, or figuring out how much something dropped. Whatever the numbers, enter your old and new value above and get your answer.
How to use the calculator
- → Enter your old value (A) — the starting point.
- → Enter your new value (B) — the value after the change.
- → Click Calculate.
- → Get your answer instantly, including the formula and full calculation steps.
Why use this percentage change calculator?
- ✓ Free & unlimited — no sign-up, no hidden limits
- ✓ Instant results — calculation shown in real time
- ✓ Shows the full formula — not just the answer
- ✓ Works with any currency or unit — €, $, £, kg, %, or plain numbers
- ✓ Doubles as both a percentage increase and a percentage decrease calculator, depending on which direction your numbers move
Why this calculation matters
Percentage change shows up everywhere — payslips, rent increases, weight tracking, news headlines, business reports. But raw numbers alone don't tell you much. Knowing your rent went from €800 to €850 is one thing; knowing that's a 6.25% increase is what actually lets you compare it to inflation, your raise, or last year's increase. It's the same thinking behind working out how much a stock moved, how much a discount really saved you, or how a company's revenue growth compares year over year.
Common uses for this calculator
- Rent and membership fees – "Rent rose from €800 to €850, what percentage is that?"
- Weight change – "From 80 kg to 74 kg — what percentage was lost?"
- Price trends – "Gas price rose from €1.50 to €1.80", "Electricity bill rose from €60 to €75"
- Population or employee growth – "Population rose from 20,000 to 21,500, what's the percentage change?"
- Business growth – "Followers rose from 1,000 to 1,500", "Website traffic grew from 500 to 800 visits a day"
- Revenue or salary comparisons – "Revenue fell from €12,000 to €10,200, what percentage decline is that?"
The formula
A positive result means an increase; a negative result means a decrease — the same formula whether you're calculating a rise from one number to another or a drop between two values.
Step-by-step example
Task: Change from €80 to €100.
- Step 1: €100 − €80 = €20 (difference)
- Step 2: €20 ÷ €80 = 0.25
- Step 3: 0.25 × 100 = 25%
A more detailed real-world example
Problem: The electricity price rose from €60 to €75. Six months later it drops back down to €70. What's the percentage change at each stage?
Step 1 – First change (€60 → €75):
€75 − €60 = €15 (difference)
€15 ÷ €60 = 0.25
0.25 × 100 = 25% increase
Step 2 – Second change (€75 → €70):
€70 − €75 = −€5 (difference)
−€5 ÷ €75 = -0.0667
-0.0667 × 100 = -6.67% decrease
For the second step, €75 becomes the new reference value — that's why the drop back to €70 works out to -6.67% rather than a clean -5%. This is exactly the kind of thing that trips people up when comparing two price changes back to back, or tracking how a value moved over several months.
Have your own numbers to check? Click here and run them through the calculator — free, with no limits.
Common mistakes when calculating percentage change
- A 20% increase followed by a 20% decrease does NOT bring you back to the starting value. €100 + 20% = €120. Subtracting 20% from €120 gives you €96 — not €100, because the second calculation uses the new, higher value as its base. This is the same reason combined discounts don't add up the way people expect.
- Percentage points and percent are not the same thing. If an interest rate rises from 5% to 7%, that's a 2 percentage point difference. Relatively speaking, that's actually a 40% increase (2 ÷ 5 × 100) — a distinction worth knowing next time you read about inflation or unemployment figures.
- A rise and its exact reversal aren't the same percentage. A rise from €80 to €100 is +25%. A fall from €100 back to €80 is only −20%, even though the euro amount is identical, because the base value is different each time. The same logic applies whether you're watching a stock price, a currency rate, or a monthly budget.
Why trust this calculator
This calculator uses the standard percentage change formula used in finance, statistics, and everyday business reporting: ((New − Old) ÷ Old) × 100. Every result shows the full step-by-step calculation, so you're not relying on a black-box answer.
One edge case worth knowing: if the old value is 0, percentage change can't be calculated, since the formula requires dividing by the old value, and division by zero is undefined. In that case, the change is usually described in absolute terms instead — "increased by €50," for example — rather than as a percentage.
Frequently Asked Questions (FAQ)
1. How do I calculate the percentage change between two values?
Subtract the old value from the new value, divide the result by the old value, and multiply by 100. Formula: ((New − Old) ÷ Old) × 100.
2. What does a negative result mean?
A negative result indicates a decrease. For example, −15% means the value has dropped by 15%.
3. Why doesn't a 25% increase followed by a 25% decrease bring you back to the original value?
Because the second calculation uses the already-increased value as its base, not the original one. The final value ends up lower than where you started — a common trap when working out two changes back to back.
4. What's the difference between percent and percentage points?
Percentage points describe the absolute difference between two percentages (e.g., 5% to 7% = 2 percentage points). Percent describes the relative change (in this case, 40%). These get mixed up constantly in news about interest rates, unemployment, or survey results.
5. How do I calculate percentage change over several years (growth rate)?
For one overall change across multiple years, use the same formula with the start and end values. For an average annual growth rate, use: (End value ÷ Start value)^(1 ÷ Number of years) − 1.
6. What happens if the old value is 0?
The formula doesn't work in this case, since it requires dividing by the old value. A change from 0 to any number is usually reported as an absolute increase rather than a percentage.
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Last updated: August 13, 2026