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Reverse percentage calculator

Find the whole when you know that a value is a given percentage of it.

Related tools

All Percentages & ratios tools →
Percentage change calculatorFind the percentage increase or decrease between two numbers.Percentage decrease calculatorHow far a value fell from an old figure to a new one, as a percentage — and the absolute drop. A negative result means it actually rose.Percentage difference calculatorCompute the percentage difference between two values (relative to their average).Percentage error calculatorCompute the percentage error between a measured and a true value.Percentage increase calculatorBy how much a value grew from an old figure to a new one, as a percentage — and the absolute change. A negative result means it actually fell.Percentage calculatorFour percentage calculations in one: X% of Y, what percent X is of Y, and increasing or decreasing a value by a percentage.Percentage point change calculatorFind the difference in percentage points between two percentages, and the relative change.Mass percent calculatorCompute the mass percent of a solute in a solution.

Enter Known value, is this percent (%) and the Reverse percentage calculator works out Of this whole straight away. For instance, with Known value = 25 and is this percent (%) = 20 it returns Of this whole = 125.

How to use it

  1. Enter your values: Known value, is this percent (%).
  2. Read the result instantly: Of this whole.

Frequently asked questions

How does the Reverse percentage calculator work?

It takes Known value and is this percent (%) and derives Of this whole from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

2 values: Known value and is this percent (%). Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Known value = 25 and is this percent (%) = 20, the calculator returns Of this whole = 125. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

How much does the result change with different inputs?

It moves a lot. Using Known value = 50 and is this percent (%) = 22 instead, Of this whole goes from 125 to 227.273 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Known value = 13 and is this percent (%) = 18, Of this whole comes out at 72.222. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

The everyday cases: a discount at the till, a rise or fall between two figures, the price before tax, and working backwards from a total.

What is the most common mistake?

Undoing a percentage by applying it again. Take 20% off 100 and you get 80; add 20% to 80 and you get 96, not 100 — the two operations use different bases.

What is the difference between the Reverse percentage calculator and the Percentage change calculator?

This one returns Of this whole; the Percentage change calculator returns Change and Difference. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Percentage decrease calculator is the closest one after this: How far a value fell from an old figure to a new one, as a percentage — and the absolute drop. A negative result means it actually rose.

What else is worth having open alongside it?

Percentage difference calculator and Percentage error calculator — they come up in the same task often enough to be worth a second tab.

Further reading

All guides →
How-toHow to Calculate a Percentage: 4 Methods with ExamplesA clear guide to percentages: find X% of a number, work out what percent one number is of another, and add or subtract a percentage — with worked examples.How-toPercentage Change: Increase and DecreaseSubtract old from new, divide by the old value, times 100. Here's the formula, why increases and decreases aren't symmetric, and where it's used.ExplainerPercentage Difference vs. Percentage Change vs. Percentage ErrorThree percentages that look alike but answer different questions. Learn the formula for each, when to use it, and why they give different numbers.ExplainerPercentage Points Are Not PercentMoving from 4% to 5% is a rise of one percentage point and a rise of twenty-five percent. Both statements are true, which is exactly why the ambiguity is so easy to exploit — and why basis points exist.How-toHow to Calculate Percent Error: The Accuracy Formula for SciencePercent error tells you how close a measurement is to the true value. Learn the formula, work through an example, and see how scientists use it to judge accuracy.ExplainerStacked Discounts Do Not Add UpTwenty percent off and then a further ten percent off is not thirty percent off — it is twenty-eight, because the second discount applies to the already-reduced price. The general rule, the cases where order matters, and how sales tax changes the answer.