Math & Statistics

Percentage Calculator

Handles the four percentage questions people actually ask, over a whole list at once.

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How to use this tool

  1. Choose which of the four calculations you want.
  2. Paste your pairs, two numbers per line.
  3. Select Calculate.
  4. Read the absolute change in the last column alongside the percentage — a large percentage on a small base is often not the story it looks like.

What percentage calculator does

Four calculations cover almost every percentage question: the change from one figure to another, one figure as a share of another, a percentage of a figure, and the reverse — recovering the value that existed before a stated increase. Pick the mode once and paste as many pairs as you like, which is the part a phone calculator cannot do.

The absolute change is printed beside the percentage deliberately. Percentage changes do not cancel — a 50% rise followed by a 50% fall leaves you a quarter down, not level — and having the raw difference in the same row is the quickest guard against that mistake. Division by zero is reported as undefined rather than shown as a number.

Frequently asked questions

Because each is calculated on a different base. Starting at 100, a 50% rise gives 150, and a 50% fall from 150 gives 75 — a quarter below where you started. Percentage changes compound rather than add, which is why the absolute change is shown in the same row.

Use the reverse mode. Give it the figure after the change and the percentage that was applied, and it divides rather than subtracting — which is the point, since taking 20% off a price that had 20% added does not return the original.

Because there is no percentage that describes going from nothing to something — every answer would be infinite. Reporting it as undefined is honest; the absolute change is the figure to quote in that case.