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Percentage Calculator

Work out a percentage of a number, what percent one number is of another, or the percentage change between two figures.

Your Inputs

Calculation
%

For example 15 for 15%.

The number you are taking a percentage of.

Your Results

Result
30

15% of 200 is 30.

About the Percentage Calculator

Publishing throws up percentage questions all the time. How much did royalties grow from last month? What share of your sales came from Amazon.co.uk? How much is a 15% agent or co-author share of a payment? This calculator answers all three kinds of question with one tool, so you do not have to remember which number goes on top.

Pick the calculation, type your two numbers and read the answer as a figure and as a plain sentence you can copy into a report, a spreadsheet note or a message to a co-author. For percentage change it also shows the raw difference, so you can see both "up 30%" and "up $126" at a glance.

For money-specific work, such as adding VAT or splitting a royalty payment in a particular currency, the Currency Percentage Calculator formats results in that currency. For price promotions, the Discount Calculator also shows how a sale changes your royalty.

How It Works

X% of Y multiplies Y by X divided by 100. Use it for shares, commissions and simple splits.

X is what % of Y divides the part by the whole. The whole cannot be zero, because a share of nothing has no meaning.

% change divides the difference between the new and original values by the original value. A positive result is an increase and a negative result is a decrease. The original value cannot be zero.

Formula

X% of Y
Result = (X ÷ 100) × Y
X is what % of Y
Percentage = (X ÷ Y) × 100
% change
Change = ((New − Original) ÷ |Original|) × 100

Example

Month-on-month royalty growth

  1. Choose % change.
  2. Original value: 412 (last month's royalties in dollars).
  3. New value: 538 (this month's royalties).
  4. Difference: 538 − 412 = 126.
  5. Change: 126 ÷ 412 = 0.3058, or 30.58%.

Royalties rose by about 30.58%, an increase of 126 dollars.

Important Notes

  • Results are shown to up to four decimal places of a percent. Round them as your report requires.
  • Percentage change is measured against the original value, so a rise from 100 to 150 (+50%) followed by a fall back to 100 is a 33.33% decrease, not 50%.
  • Negative numbers are accepted, which is useful for comparing losses or refunds.
  • Very large inputs are rejected to keep results accurate.

Frequently Asked Questions

Why is a 50% increase followed by a 50% decrease not back where I started?

Each change is measured against a different starting point. 100 up 50% is 150, and 150 down 50% is 75. Use the % change mode with your real before and after figures to see the true change.

How do I compare sales between two marketplaces?

Use **X is what % of Y** with one marketplace's sales as the part and your total sales as the whole. For example, 85 copies out of 340 total is 25%.

What is the difference between percentage change and percentage points?

If your conversion rate moves from 10% to 12%, that is a change of 2 percentage points but a 20% increase. This calculator reports the relative change, so enter 10 and 12 to get 20%.

Can I use it for page-read or KENP trends?

Yes. Any two numbers work, including Kindle Unlimited page reads, ad clicks or newsletter subscribers. Enter the earlier period as the original value.

Why do I get an error when the original value is zero?

Growth from zero has no meaningful percentage, because any increase is infinitely large in relative terms. Report the raw difference instead.

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