A 50% drop needs 100% back
Fall from 100 to 50? You must double (100%) to return—percentage change is always relative to the starting point.
Base effect
Percentage Change Calculator — Increase/Decrease from Old to New
Inputs & Actions
Starting value (can be negative). Uses |V₁| in the formula.
Applies to the percent output.
Result will appear here.
Formula: ((V₂ − V₁) ÷ |V₁|) × 100.
Tips: Ctrl/Cmd + Enter = Calculate · Esc = Clear
Breakdown
Enter values to see the step-by-step calculation and sign (increase/decrease).
Examples
- From 120 to 150 →
((150 − 120) ÷ 120) × 100 = 25%increase. - From 80 to 50 →
((50 − 80) ÷ 80) × 100 = −37.5%decrease. - From −40 to −20 →
((−20 − (−40)) ÷ 40) × 100 = 50%increase. - From 0 to 10 → change from zero is conceptually “infinite” (% undefined).
Understanding Percentage Change
Percentage change tells you how big a shift is compared with where you started. It answers a simple question: if something went from one value to another, what percent increase or percent decrease is that? This makes it easy to compare changes across different sizes, whether you are tracking prices, test scores, website traffic, or any other numeric trend.
The idea behind the calculation
The formula is based on the difference between a new value and the original value, divided by the original
value, then multiplied by 100 to convert to a percent:
((New − Old) ÷ |Old|) × 100.
Using the absolute value of the original helps handle negative starting numbers in a consistent way.
A positive result means an increase, and a negative result means a decrease.
For example, moving from 120 to 150 is a 25% increase because the change is 30, and 30 is one quarter of 120. Moving from 80 to 50 is a 37.5% decrease because the change is −30 relative to 80. If the original value is zero, a percentage change is undefined because you cannot divide by zero, which is why the calculator flags that case.
How to use this percentage change calculator
- Enter the original value (V1) in the first input.
- Enter the new value (V2) in the second input.
- Click Calculate to see the percent change and whether it is an increase or decrease.
The calculator works entirely in your browser, so your inputs stay on your device. It also accepts negative values, which is helpful for things like temperature changes, profit and loss, or net gains and losses.
Real-world uses
Percentage change shows up in everyday decisions. Investors compare price changes in stocks or crypto, businesses track revenue growth and conversion rates, and students measure improvement from one test to the next. In health and fitness, it can describe weight change over time. In science, it is a quick way to express how much a measurement increased or decreased between trials. By converting raw differences into percent, you get a clear, comparable rate of change that is easy to interpret.
Frequently Asked Questions
What is percentage change?
It’s the percent difference between a starting value and an ending value. Positive results mean an increase; negative results mean a decrease.
What’s the difference between % change and % difference?
Percentage change compares against the original value, while percentage difference compares the difference to the average of the two values.
Can this handle negative numbers?
Yes — the absolute value in the formula ensures the change is calculated relative to the magnitude of the original value.
Are my inputs private?
Absolutely. All calculations are performed locally in your browser — nothing is sent to our servers.
5 Fun Facts about Percentage Change
Zero makes infinity
Any non-zero jump from 0 makes the percent change conceptually infinite, which is why the calculator flags it as undefined.
Math quirk
Compounding hides in plain sight
A steady 1% daily increase is +37.8x over a year (≈3,678%). Small changes stack explosively.
Everyday exponential
Negative starts still work
Using |Old| in the formula lets you compare changes from negative baselines—handy for net losses flipping to gains.
Handles negatives
Rounding can flip the story
A 0.49% dip rounds to 0% at one decimal, but a 0.51% rise rounds to +0.5%. Precision settings shape the headline.
Data storytelling