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Percentage Change Calculator

Work out the percentage increase or decrease between an old and a new value. See the absolute change and whether it went up or down, instantly and privately.

+25%
Percentage change
+10
Absolute change
increase
Direction

How it was calculated

(50 − 40) ÷ |40| × 100 = 25%

The value went from 40 to 50, a increase of 10.

What is the Percentage Change Calculator?

The ByteTools Percentage Change Calculator finds how much a value has risen or fallen in percentage terms.

  • Percentage increase or decrease between two values
  • Shows the absolute change as well as the percentage
  • Clearly labels the direction (up or down)
  • Handles negative values and decimals
  • Explains the edge case when the old value is zero
  • 100% private — runs entirely in your browser

How to use the Percentage Change Calculator

  1. 1

    Enter the original (old) value.

  2. 2

    Enter the new value to compare against it.

  3. 3

    Read the percentage change and whether it is an increase or decrease.

  4. 4

    Check the absolute change and the worked formula below.

  5. 5

    Click Copy to grab the result.

About the Percentage Change Calculator

The ByteTools Percentage Change Calculator finds how much a value has risen or fallen in percentage terms. Enter the original (old) value and the new value, and it returns the percentage change, whether that is an increase or a decrease, and the absolute difference between the two numbers.

It is handy for tracking price rises, salary changes, statistics, weight loss, investment returns and any before-and-after comparison. The tool spells out the calculation so you can see exactly how the percentage was derived, not just the final figure.

Everything runs entirely in your browser with JavaScript. No numbers are uploaded or stored, so the calculator is fast, private and works offline. Copy the result with a single click.

Frequently asked questions

How do you calculate percentage change?

Subtract the old value from the new value, divide by the absolute old value, then multiply by 100. For example, from 40 to 50 the change is (50 − 40) ÷ 40 × 100 = 25% increase. The calculator applies this formula and shows each step.

What is the difference between percentage change and percentage difference?

Percentage change measures how much one value moved relative to a starting value, so it has a direction. Percentage difference compares two values without a defined starting point, dividing by their average. This tool calculates percentage change from old to new.

How do you find a percentage decrease?

When the new value is smaller than the old one, the percentage change is negative, which is a decrease. From 200 to 150 the change is (150 − 200) ÷ 200 × 100 = −25%, a 25% decrease. The tool labels the direction for you.

What happens when the old value is zero?

Percentage change is undefined when the starting value is zero, because you cannot divide by zero. Going from 0 to any number is an infinite percentage increase, so the calculator flags this and reports the absolute change instead.

Can percentage change be more than 100%?

Yes. If a value more than doubles, the increase is over 100%. Rising from 50 to 150 is a 200% increase, because the change (100) is twice the original value. The tool handles values of any size.

Guides for Percentage Change Calculator

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