Percentage Change Calculator
Technical Calculation Methodology and Tool
Interactive Percentage Change Calculator
Calculate percentage increase or percentage decrease between two numbers instantly.
Percentage Change Calculator
Calculate the % increase or decrease between two values
Tracking a price movement, measuring sales growth, or checking whether last month's actuator output numbers improved — the raw difference between 2 values tells you nothing useful on its own. You need the relative change. Use this Percentage Change Calculator to calculate percentage increase or decrease using a starting value and an ending value. It matters everywhere numbers move: retail pricing, engineering performance benchmarks, financial reporting, and project KPIs. This page includes the formula, worked examples, a results table, common mistakes, and a full FAQ.
What is percentage change?
Percentage change is a number that tells you how much a value has gone up or down relative to where it started — expressed as a percentage. A positive result means it increased; a negative result means it decreased.
Simple Explanation
Think of it like checking whether your electricity bill got better or worse this month. If it went from $100 to $120, you want to know it jumped by 20% — not just by $20. Percentage change gives you that relative picture so you can compare movements fairly, even when the original numbers are very different sizes.
How to Use This Calculator
- Enter your original or starting value in the first field.
- Enter the new or ending value in the second field.
- The calculator automatically applies the percentage change formula and shows whether the result is an increase or decrease.
- Click Calculate to see your result.
What Is Percentage Change?
Percentage change measures how much a number has increased or decreased relative to its starting point. It is commonly used for prices, revenue, traffic, conversion rates, population changes, costs, profits, and test scores.
A positive result means the value increased. A negative result means the value decreased. This makes percentage change one of the most useful ways to compare movement between two numbers of different sizes.
The Percentage Change Formula
Use the formula below to calculate percentage change.
The vertical bars around the old value mean we use the absolute value of the starting number. This avoids sign issues when the original number is negative.
Simple Example
Starting value: 50 — Ending value: 75
Difference: 75 − 50 = 25
Divide by starting value: 25 ÷ 50 = 0.5
Result: 0.5 × 100 = +50% increase.
Step-by-Step Calculation
- Subtract the starting value from the ending value to find the difference.
- Divide that difference by the absolute value of the starting value.
- Multiply the result by 100.
- Interpret the sign: positive means increase, negative means decrease.
Worked Examples
A coffee that cost $3.50 last year now costs $4.20. What is the percentage increase?
Result: +20% increase.
A TV was $1,200 and is now $900. What is the percentage decrease?
Result: −25% decrease.
Your store made $8,400 last month and $10,500 this month. What is the growth rate?
Result: +25% growth.
A student's score changed from 88 to 77. What is the percentage change?
Result: −12.5% decrease.
Results Table
| Starting Value | Ending Value | Difference | % Change |
|---|---|---|---|
| 50 | 75 | 25 | +50% |
| 80 | 60 | -20 | -25% |
| 3.5 | 4.2 | 0.7 | +20% |
| 88 | 77 | -11 | -12.5% |
Common Mistakes to Avoid
- Using the wrong base: Always divide by the original value, not the new one.
- Confusing percentage change with percentage points: A move from 10% to 15% is 5 percentage points, not 5% change.
- Ignoring the sign: Positive means increase, negative means decrease.
- Trying to divide by zero: Percentage change is undefined when the original value is zero.
Quick Answers
What is the percentage change from 50 to 75? +50%
What is the percentage change from 80 to 60? -25%
What is the percentage change from 1,200 to 900? -25%
What is the percentage change from 3.5 to 4.2? +20%
Percentage Change vs Percentage Points
If a store's discount rate changes from 10% to 15%, that is a change of 5 percentage points, but the discount rate itself increased by 50%. These are very different measurements, and using the wrong one can mislead readers or customers.