ToolBirch

Percentage Change Calculator

Measure the percent increase or decrease between two values.Calculators

Percentage Change Calculator

Measure the change from an old value to a new one as a percentage, with the direction labelled.

0%

The values are equal.

About this tool

Enter the old and new value to get the relative change in percent, signed and labelled. The zero-base case — where percentage change is mathematically undefined — is explained rather than shown as an infinity.

How to use the Percentage Change Calculator tool

  1. Enter the old value. The base the change is measured against.
  2. Enter the new value. The value you are comparing to.
  3. Read the change. A signed percentage with its direction, updated as you type.

Supported formats

Input

  • Two numeric values

Output

  • Percentage change
  • Direction (increase / decrease / unchanged)

Inputs are validated before anything is processed. Invalid values and unsupported files are rejected with a clear error instead of failing silently.

Frequently asked questions

How is the change computed?

As (new − old) ÷ |old| × 100, the standard relative-change formula.

Why is a zero base undefined?

Dividing by zero has no defined percentage; the tool explains this instead of showing an infinite value.

Does the sign mean direction?

Yes. Positive results are increases, negative results are decreases.

Can I use negative values?

Yes; the absolute base keeps the direction intuitive for negative starting points.

Privacy

Everything you enter stays in this browser tab. There is no upload endpoint for tool inputs, no account, and no server-side copy of your text or files. Results are produced locally and disappear when you close the page.

No account is required and no file is ever uploaded. See the privacy policy for details about analytics and the limited data this site stores.

Known limitations

  • A zero base with a non-zero new value is reported as undefined.
  • Results show up to four decimal places without further rounding rules.
  • This is a single comparison; multi-period trends are not charted.

Related tools

Other free tools from the same collection.

Percentage CalculatorWork out percentages, percentage of a value and percent changes.Discount CalculatorFinal price after a discount — or the original price before it.Compound Interest CalculatorProject a balance with interest frequency and optional deposits.Unit ConverterConvert length, mass, temperature and data units precisely.