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KioTools
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Percentage Calculator

What is this tool?

A plain percentage calculator that covers the three questions people actually search for. Each one updates as you type, and every calculation runs locally in your browser.

When to use it

  • Working out a discount, tip or tax amount from a percentage
  • Finding what share one figure is of a total (for example a test score)
  • Measuring growth or decline between two numbers, like month-over-month revenue
  • Checking a markup or margin percentage
  • Double-checking a percentage in a spreadsheet or report

How to use it

  1. 1For 'X% of Y', enter the percentage and the value
  2. 2For 'X is what percent of Y', enter the part and the whole
  3. 3For percentage change, enter the starting value and the ending value
  4. 4Read each answer in the results panel as you type
  5. 5Adjust any field to see the result recalculate instantly

Frequently asked questions

How is percentage change calculated?

As (new - old) / |old| x 100, so a change from 80 to 100 is +25% and from 100 to 80 is -20%.

What happens if I divide by zero?

Calculations that would divide by zero (like 'what percent of 0') show a dash instead of a misleading number.

Does it round the results?

Results are shown to two decimal places, with trailing zeros trimmed for readability.

Is anything sent to a server?

No — all three calculators run entirely in your browser.