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.
How to Calculate Percentage Change
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. If you need to calculate simple percentages, proportions, or portions of a base number, try our main percentage calculator.
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.
Percentage Increase and Decrease
A positive percentage result indicates growth (percentage increase), while a negative value represents a decline (percentage decrease). For price reductions and retail markdowns, you can also use our dedicated discount calculator to determine exact cash savings and final checkout prices.
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
The Percentage Change 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%
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