Percentage Calculator
Works out percentage of, percentage change, discount, markup and reverse percentage in one place.
The seven percentage questions people actually ask, each with its own set of fields so you are never wondering which number goes where. Includes the two that are easy to get backwards: undoing a percentage, and the difference between margin and markup.
Question
Numbers
Answer
15% of 80,000 is 12,000
How to use it
Pick the question
X% of Y, X is what % of Y, percentage change, increase or decrease, undo a percentage, margin versus markup, or several changes in a row. The field labels change with it.
Fill in the two numbers
Each mode names its own fields — Cost and Selling price for margin, Value after the change for undoing one — so there is no ambiguity about which is the base. The numbers themselves are read the way this page’s language writes one: here the comma groups the thousands and the dot marks the decimal, so 80,000 and 1.5 both go straight in, and 1,5 is refused rather than read as fifteen. On the pages whose language marks the decimal with a comma — Spanish, Portuguese, German, French, Italian — it is the other way round, and the several-changes box separates its list with semicolons instead, the way those spreadsheets do.
Read the working, not just the answer
The formula is printed with your numbers substituted in. That is what lets you check the tool rather than trust it, and what you paste into an email when someone asks how you got there.
Common questions
Up 10% then down 10% is not the original. Why?
Because the second percentage is taken from a bigger number. 100 up 10% is 110, and 10% of 110 is 11, so you land on 99. The several-changes mode shows this chain and the single equivalent rate, which is −1%.
What is the difference between margin and markup?
The base. Markup is profit over cost; margin is profit over selling price. A 50% markup is a 33.3% margin, and quoting one when you meant the other is how a business talks itself into a loss.
How do I get the price before a discount?
Use Undo a %. Dividing by 0.8 is right for a 20% discount and multiplying by 1.2 is wrong — it gives 96% of the original, an error of one part in twenty-five that goes unnoticed for a long time.
Percentage points or per cent?
From 4% to 5% is one percentage point and a 25% increase. The change mode reports both, because a headline that says "up 25%" and one that says "up one point" can describe the very same number.
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