Percentage Calculator

How to use 3 steps

Enter the percentage under What is X %.
Enter the Of Total Amount Y.
Press Calculate Percentage.

What is X %:

Of Total Amount Y:

Percentage Calculation Result

How this tool works

Enter a percentage and a total and you get two figures: that percentage of the total, and what share the first number is of the second.

The two outputs answer different questions from the same pair of inputs, which is worth understanding before reading them. The first multiplies: 20 and 50 gives 10, because twenty per cent of fifty is ten. The second divides: the same pair gives 40%, because twenty is forty per cent of fifty. Both are shown because the numbers people type are usually ambiguous about which they meant. A total of zero is rejected rather than returning infinity.

Percentages that mislead

Percentage of and percentage that are not the same: twenty per cent of fifty is ten; twenty as a share of fifty is forty per cent. Both appear in the result, so read the labels.
A rise then an equal fall does not return to the start: 100 raised by 10% is 110, and 110 reduced by 10% is 99. The base changes between the two steps.
Percentage points are not percentages: moving from 5% to 7% is two percentage points, which is a forty per cent increase. Reports conflate these constantly.
Averaging percentages needs the underlying counts: a 50% rate from two cases and a 50% rate from two hundred do not average to a meaningful 50%. Add the numerators and denominators instead.

The same two numbers answer two different questions

Enter a percentage and a total into the [msm_tool slug="percentage-calculator"] and two figures come back, because the pair of numbers genuinely supports two different questions. "What is 20% of 50?" multiplies, giving 10. "What percentage is 20 of 50?" divides, giving 40%. Both are shown together specifically because the numbers people type in are usually ambiguous about which question was actually meant.

A rise then an equal fall does not return to the start

Raising 100 by ten per cent gives 110, and reducing 110 by ten per cent gives 99, not 100 — the second percentage is calculated against a different, larger base than the first one was. The two operations use the same percentage but different starting points, which is exactly what breaks the intuition that they should cancel out.

Percentage points are not percentages

Moving from 5% to 7% is a rise of two percentage points, and it is also a forty per cent increase relative to where it started — both descriptions are correct, and they are frequently swapped for each other in reporting in a way that makes a change look far smaller or far larger than it actually was. The two figures answer different questions about the exact same move.

Percentages from different-sized groups cannot simply be averaged

A fifty per cent rate drawn from two cases and a fifty per cent rate drawn from two hundred do not average into a meaningful fifty per cent, because the two rates do not represent the same amount of evidence. Adding the underlying numerators and denominators together first, then taking the percentage of the combined total, is what actually reflects the full picture.

Why a total of zero is refused rather than answered

A share of nothing has no defined value, so a total of zero is rejected outright rather than the tool returning infinity or, worse, a plausible-looking zero that quietly means something different from every other zero it might display.

Frequently Asked Questions

Specific to the Percentage Calculator. Broader questions about this category are answered on the category page.

How do I work out what percentage one number is of another?

Divide the part by the whole and multiply by a hundred. The second figure in the result does this for the two numbers you entered, so it is available without rearranging anything.

Why does a 10% increase followed by a 10% decrease not return to the original?

Because the second percentage is taken from the larger figure. Ten per cent of 110 is more than ten per cent of 100, so the fall is bigger than the rise and you finish one per cent below where you started.

What is the difference between per cent and percentage points?

Per cent is relative to a base; a percentage point is an absolute step on a percentage scale. An interest rate moving from 4% to 6% has risen two percentage points, or fifty per cent, and both statements are true of the same change.

Why is a total of zero rejected?

Because a share of nothing is undefined — the division has no answer. The tool reports this rather than displaying infinity or a misleading zero.

Does the calculation happen on a server?

No. It runs in your browser and nothing is transmitted.