Percentage Change Calculator
Calculate the percentage increase or decrease between two values.
The value increased by 20.0% from 100 to 120.
Why This Calculation Matters
The Percentage Change Calculator gives you a fast, accurate answer for percentage change, useful for homework, coursework, or inside a larger problem. The formula is shown below so you can see exactly what the tool is doing and verify it against a textbook or other reference.
How to Use This Calculator
- Enter your values in the input fields, each one has a label and help text explaining what to type.
- Results appear instantly as you type; there's no "calculate" button to press.
- Change any input to compare scenarios side by side.
All math happens in your browser. Nothing you type is sent to a server, saved, or shared.
Percentage Change Formula
% Change = [(New Value, Old Value) / Old Value] × 100
Examples
- From 100 to 125: +25% increase
- From 100 to 75: -25% decrease
- From 50 to 150: +200% increase
Formula
Percent change = ((new − old) ÷ old) × 100. A drop from 100 → 50 is −50%; a rise from 50 → 100 is +100%. The same absolute change is a different percentage depending on the starting point.
Worked Example
A price moves from $80 to $100.
- Starting value
- 80
- Ending value
- 100
- Result
- +25%
((100 − 80) ÷ 80) × 100 = 25%.
When to Use This Calculator
- Check homework, textbook problems, or coursework answers.
- Explore how the result changes as you vary inputs, great for intuition building.
- Verify a calculation inside a larger engineering, research, or data workflow.
Limitations & Common Mistakes
- Results are only as accurate as the inputs, double-check rounding and units.
- Numeric precision is limited by JavaScript floating-point arithmetic.
Frequently Asked Questions
What is the difference between percentage change and percentage difference?
Percentage change measures the change from a specific starting value (directional). Percentage difference measures the difference between two values relative to their average (non-directional). Use change when there's a clear "before" and "after."
What is the formula used by the Percentage Change Calculator?
The formula and a worked example are shown on this page. Results are computed with standard floating-point arithmetic and are accurate to several decimal places for typical inputs.
Can I use this for homework or standardized tests?
Yes, it's an excellent check-your-work tool. Always show your work and understand the underlying method, not just the final number.
Is this calculator free to use?
Yes. The Percentage Change Calculator is free, requires no signup, and runs entirely in your browser, your inputs are never sent to a server.
How often is this calculator updated?
Formulas are reviewed against authoritative sources, and any rate or price data is refreshed on an automated schedule. Check the "as of" date on any live data panel for the most recent refresh.
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