Percentage Increase/Decrease Calculator
Use this calculator in two ways: compare two values to find percentage increase or decrease, or apply a percentage change to a single value.
1) Find Percentage Change Between Two Values
2) Apply Increase or Decrease to a Value
How to Calculate Percentage Increase and Decrease
A percentage increase or percentage decrease tells you how much a number has changed relative to its starting value. This is one of the most useful math skills for everyday life: budgeting, shopping, salary comparisons, exam scores, investing, business metrics, and more.
When people ask, “How much did this go up?” or “How much did this drop?”, they are usually asking for percentage change.
The Core Formula
To find the percentage change from an original value to a new value, use:
Percentage Change = ((New Value - Original Value) / Original Value) × 100
- If the result is positive, it is a percentage increase.
- If the result is negative, it is a percentage decrease.
- If the result is zero, there is no change.
Quick Examples
Example 1: Increase
Your monthly internet bill goes from $60 to $75.
((75 - 60) / 60) × 100 = (15 / 60) × 100 = 25%
This is a 25% increase.
Example 2: Decrease
A product price drops from $120 to $90.
((90 - 120) / 120) × 100 = (-30 / 120) × 100 = -25%
This is a 25% decrease.
Example 3: Applying a Percentage
If a value is 200 and you increase it by 10%:
New Value = 200 × (1 + 10/100) = 220
If you decrease 200 by 10%:
New Value = 200 × (1 - 10/100) = 180
Common Mistakes to Avoid
- Using the wrong base: Always divide by the original value when calculating percentage change.
- Confusing percentage points with percent: Moving from 20% to 25% is a 5 percentage-point increase, but a 25% relative increase.
- Thinking opposite percentages cancel out: A 50% decrease followed by a 50% increase does not return to the original value.
- Ignoring signs: A negative result means decrease, a positive result means increase.
Where This Calculator Helps in Real Life
Personal Finance
Track spending, evaluate subscription cost changes, compare utility bills, and measure savings growth over time.
Shopping and Discounts
Check whether a sale price is really a good deal, and compare discount percentages between stores.
Salary and Career
Find the percentage raise between two salaries, or determine how much a pay cut affects take-home income.
Business and Marketing
Measure revenue growth, conversion rate changes, customer churn reduction, and performance trends across periods.
Reverse Calculations (Useful Trick)
Sometimes you know the final value and percentage change, and need the original value.
- After an increase: Original = New / (1 + p/100)
- After a decrease: Original = New / (1 - p/100)
Example: A jacket now costs $72 after a 20% discount. Original price:
Original = 72 / (1 - 0.20) = 72 / 0.80 = 90
FAQ
Can percentage change be more than 100%?
Yes. If a value more than doubles, the increase exceeds 100%.
What if my original value is zero?
Percentage change from zero to a non-zero value is undefined (division by zero). The calculator will flag this clearly.
Should I use absolute value in the denominator?
In most everyday contexts, the original value is positive and standard formula works directly. For special analytical cases with negative baselines, interpretation depends on context.
Final Thoughts
A reliable percentage increase decrease calculator saves time and prevents mistakes, especially when comparing prices, tracking growth, or planning budgets. Use the tool above whenever you need fast, accurate results—and keep the formula handy so you always understand what the numbers mean.