Skip to tool content
Toolioz logoToolioz
Growth and decline analysis

Percentage Increase or Decrease Calculator

Measure the percentage change from an original value to a new value with the full calculation shown.

Enter Known Values

Calculated in this tab
Calculated Result

Percentage increase

25%

((100 − 80) ÷ |80|) × 100
Absolute change
20
Direction
Increase
Quick Summary & Direct Answer
Percentage Calculators

How is percentage increase or decrease calculated?

Percentage change measures the difference relative to the original value. Subtract the original from the new value, divide by the absolute original value, and multiply by 100. Positive results are increases; negative results are decreases.

Key Takeaways

  • Enter the original value before the change occurred.
  • Enter the new value after the increase or decrease.
  • Review the signed percentage, direction, absolute difference, and working.

How is percentage increase or decrease calculated?

The original value is the reference point, so it must remain in the denominator. This is why a move from 80 to 100 is a 25% increase, while a move from 100 back to 80 is a 20% decrease. The changes are not symmetric because each direction uses a different starting value. The calculator also reports the absolute change so the percentage retains real-world context.

Formula

Percentage change = ((New − Original) ÷ |Original|) × 100

How to use this percentage increase or decrease calculator

  1. 1Enter the original value before the change occurred.
  2. 2Enter the new value after the increase or decrease.
  3. 3Review the signed percentage, direction, absolute difference, and working.

Percentage change examples with correct base values

Each example keeps the base value visible so the calculation can be easily verified.

ScenarioSubstituted FormulaResult
Price rises from 80 to 100((100 − 80) ÷ 80) × 10025% increase
Traffic falls from 500 to 425((425 − 500) ÷ 500) × 10015% decrease
Salary rises from 45,000 to 49,500((49,500 − 45,000) ÷ 45,000) × 10010% increase

Common percentage increase or decrease calculator Mistakes

Using the new value as the base

Percentage change is normally measured against the original value, not the final value.

Calling percentage points “percent”

A rate moving from 20% to 25% rises by 5 percentage points but increases by 25% relative to 20%.

Dividing by an original value of zero

Relative percentage change from zero is undefined; report the absolute change instead.

Method Reference: The formula used here aligns with U.S. Bureau of Labor Statistics percent-change method .

Percentage Calculator Cluster

Choose another percentage calculation

Percentage Calculator With StepsReverse Percentage CalculatorGrade Percentage CalculatorWin Percentage CalculatorWeight Loss Percentage CalculatorBody Fat Percentage CalculatorAverage Percentage Calculator

Frequently Asked Questions

Subtract the original value from the new value, divide by the original value, then multiply by 100. A positive answer indicates an increase.

Use the same percentage-change formula. When the new value is lower than the original value, the answer is negative and the calculator labels its magnitude as a decrease.

The decrease and increase use different base values. A fall from 100 to 50 is 50%, but returning from 50 to 100 requires a 100% increase.

No finite relative percentage exists when the original value is zero. The raw difference can still be stated, but division by the zero baseline is undefined.

Explore Related Tools

Car Loan EMI

Reducing-balance car-loan EMI, total interest, and total amount payable.

Try tool

Compound Interest

Future value with daily, monthly, quarterly, or annual compounding.

Try tool

Discount After Tax

Break down sale savings, tax on the reduced price, and the final amount.

Try tool

Fixed Deposit

Estimate maturity value for a fixed-rate bank deposit.

Try tool

Publisher notes · reviewed 10 September 2026

Percentage change always needs the original value in the denominator

Change = ((new − original) / |original|) × 100. A rise from 80 to 100 is +25%. A fall from 100 to 80 is −20%. They are not mirrors because the base moved.

Percentage points are not percent

A tax rate moving from 20% to 25% rose 5 percentage points and rose 25% relative to 20%. Mixing those phrases misstates a Budget speech. From zero, relative percentage change is undefined; report the absolute difference instead.

Worked examples

  • CPI-style month change

    The BLS method for percent change is the same ratio. Toolioz does not load CPI microdata; it only does the arithmetic on the two numbers you type.

Limits of this page

  • Not a chained index or seasonally adjusted series.

Sources