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DIY Cost Tools

DIY Cost Tools

Percentage Calculator

Math Calculator

Percentage Calculator

Solve percent-of, percent-share, and percentage-change problems with the formula shown beside the result.

Solve a percentage problem

Result50
Formula used25 / 100 x 200

Choose the problem type carefully: percent of, percent share, and percent change use different formulas.

How to use the percentage calculator

Choose the question you need to solve. Enter X and Y using the labels shown in the selected wording. The tool can find a percentage of a number, determine what percent one number is of another, or calculate the percentage change between an old and new value.

Percentage formulas

X percent of Y = X / 100 x Y; X as a percent of Y = X / Y x 100

Percentage change uses (new value – old value) divided by the absolute old value, multiplied by 100. A positive result is an increase and a negative result is a decrease. Percentage change is undefined when the starting value is zero.

Worked examples

Twenty-five percent of 200 is 50. If 25 is compared with 200, it is 12.5 percent of 200. If a value rises from 25 to 200, the percentage increase is 700 percent. These different answers show why the problem type matters.

Accuracy and assumptions

  • The calculator accepts positive, negative, and decimal values where the formula permits them.
  • Results are calculated before display rounding.
  • Percent share cannot divide by a zero comparison value.
  • Percentage change cannot use zero as the starting value.
  • A percentage-point change is different from percentage change.

Frequently asked questions

What is the difference between percent and percentage points?

If a rate moves from 20 percent to 25 percent, it increases by 5 percentage points but by 25 percent relative to the original rate.

Can a percentage be greater than 100?

Yes. One quantity can be more than 100 percent of another, and a value can increase by more than 100 percent.

Why use the absolute old value for percentage change?

It keeps the sign focused on whether the new value rose or fell relative to the old value. Interpret changes involving negative values carefully because context matters.

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Sources and review

The tool uses standard arithmetic definitions and displays the selected formula beside each result. Calculator logic and examples were reviewed by the DIY Cost Tools editorial team on September 28, 2026.