Percentage Increase vs. Percentage Decrease: Key Differences Explained

Percentages are commonly used to describe changes in prices, salaries, business figures, measurements, and many other situations.

Two of the most common calculations are percentage increase and percentage decrease.

Although the formulas look similar, the result depends on the original value and the direction of the change.

Understanding these calculations can help you compare numbers and interpret changes more accurately.

What Is Percentage Increase?

A percentage increase tells you how much a value has increased compared with its original value.

For example, if the price of a product increases from $100 to $120, the value has increased by $20.

The percentage increase is calculated as:

Percentage Increase = (New Value − Original Value) ÷ Original Value × 100

Using the example:

($120 − $100) ÷ $100 × 100 = 20%

Therefore, the price increased by 20%.

What Is Percentage Decrease?

A percentage decrease tells you how much a value has decreased compared with its original value.

For example, if a product's price falls from $100 to $80, the decrease is $20.

The formula is:

Percentage Decrease = (Original Value − New Value) ÷ Original Value × 100

Using the example:

($100 − $80) ÷ $100 × 100 = 20%

Therefore, the price decreased by 20%.

The Important Role of the Original Value

The original value is the reference point in a percentage change calculation.

This is important because the same numerical change can represent different percentages depending on the starting value.

For example:

• Increase from $100 to $120 = 20% increase
• Increase from $200 to $220 = 10% increase

Both changes are $20, but the percentage change is different because the original values are different.

Percentage Increase Example

Suppose an employee's monthly salary increases from $2,000 to $2,300.

First find the difference:

$2,300 − $2,000 = $300

Now divide the difference by the original salary:

$300 ÷ $2,000 = 0.15

Convert to a percentage:

0.15 × 100 = 15%

The salary increased by:

15%

Percentage Decrease Example

Imagine a product originally costs $500, but its price is reduced to $425.

First find the difference:

$500 − $425 = $75

Then:

$75 ÷ $500 × 100 = 15%

Therefore, the price decreased by:

15%

Percentage Change Formula

For a general change between two values, you can use:

Percentage Change = (Difference ÷ Original Value) × 100

The difference is determined according to whether the value increased or decreased.

For an increase:

Difference = New Value − Original Value

For a decrease:

Difference = Original Value − New Value

Percentage Increase in Business

Businesses frequently use percentage increases to measure changes in:

• Sales
• Revenue
• Expenses
• Customer numbers
• Production
• Prices
• Salaries

For example, if monthly sales increase from $50,000 to $60,000:

Difference = $60,000 − $50,000 = $10,000

Then:

$10,000 ÷ $50,000 × 100 = 20%

Sales increased by 20%.

Percentage Decrease in Business

Businesses can also use percentage decreases to measure reductions in:

• Costs
• Expenses
• Production
• Sales
• Customer numbers
• Inventory
• Prices

For example, if operating costs fall from $40,000 to $34,000:

Difference = $40,000 − $34,000 = $6,000

Then:

$6,000 ÷ $40,000 × 100 = 15%

The operating costs decreased by 15%.

Percentage Increase and Salary Raises

Percentage increases are often used when discussing salary raises.

Suppose your current salary is $3,000 per month and you receive a 10% increase.

First calculate 10%:

$3,000 × 10 ÷ 100 = $300

Then add the increase:

$3,000 + $300 = $3,300

Your new salary would be $3,300 per month, before any applicable deductions.

Percentage Decrease and Discounts

Percentage decreases are commonly used for discounts.

Suppose a product costs $250 and receives a 20% discount.

Discount:

$250 × 20 ÷ 100 = $50

Final price:

$250 − $50 = $200

The price has decreased by 20%.

Percentage Changes Are Not Always Reversible

A common mistake is assuming that a percentage increase and the same percentage decrease cancel each other out.

For example, start with $100.

Increase it by 20%:

$100 + $20 = $120

Now decrease $120 by 20%:

$120 − $24 = $96

The result is $96, not $100.

Why?

Because the 20% decrease is calculated from the new value of $120, not the original $100.

This is an important concept when analyzing price changes.

Percentage Increase and Inflation

Percentage changes are also used to describe changes in prices over time.

For example, if an item costs $50 one year and $55 the following year:

($55 − $50) ÷ $50 × 100 = 10%

The item's price increased by 10%.

Inflation measurements can involve broader collections of goods and services and use specific statistical methods, but the basic percentage-change calculation helps explain how the price of an individual item has changed.

How to Calculate Percentage Change Quickly

The basic process is:

Step 1: Identify the original value

This is your starting point.

Step 2: Identify the new value

This is the value after the change.

Step 3: Find the difference

Subtract one value from the other.

Step 4: Divide by the original value

This gives the change relative to the starting point.

Step 5: Multiply by 100

This converts the result into a percentage.

Use a Percentage Calculator

When working with larger numbers or decimal values, calculating percentage changes manually can be inconvenient.

The CalculateNow24 Percentage Calculator can help you perform percentage calculations quickly.

It can be useful for checking increases, decreases, discounts, and other everyday percentage calculations.

Common Mistakes to Avoid

Using the new value as the denominator

Percentage change is normally calculated relative to the original value, not the new value.

Forgetting to multiply by 100

A decimal such as 0.25 represents 25% when converted into percentage form.

Confusing percentage points with percentage change

These are different concepts, particularly when comparing percentages themselves.

For example, an increase from 20% to 25% is a change of 5 percentage points. The percentage increase relative to 20% would be different.

Frequently Asked Questions

What is the formula for percentage increase?

Percentage Increase = (New Value − Original Value) ÷ Original Value × 100

What is the formula for percentage decrease?

Percentage Decrease = (Original Value − New Value) ÷ Original Value × 100

Can the same percentage increase and decrease cancel each other?

No. A 20% increase followed by a 20% decrease does not return the value to its starting point because the second percentage is calculated from a different base.

What value should I use as the base?

For a standard percentage-change calculation, the original value is used as the base.

Where are percentage changes commonly used?

They are used in pricing, discounts, salaries, business reports, sales, expenses, measurements, and many other everyday calculations.

Final Thoughts

Percentage increase and percentage decrease are simple but important mathematical concepts.

The key is to always identify the original value before calculating the change.

For an increase, compare how much the value has risen relative to the original amount. For a decrease, compare how much it has fallen relative to the original amount.

Once you understand the formulas, you can use percentage changes for shopping, budgeting, salary calculations, business analysis, and many everyday situations.

For quick calculations, the CalculateNow24 Percentage Calculator can help you check your results without doing the calculation manually.