Percentage Calculator

Features

• Six calculation modes covering every common case
• Step-by-step working shown for each result
• Handles negatives and decimals
• Reverse percentages for working back from a total
• Distinguishes percentage change from percentage points

How to use it

1. Choose which calculation you need.
2. Enter the two values.
3. Read the result and the working below it.
4. Copy the answer when you are done.

Percentage change and percentage points

The most common percentage mistake is treating an increase and its matching decrease as symmetrical. They are not. A price rising from 100 to 150 is a 50% increase, but falling from 150 back to 100 is a 33.3% decrease, because the base changed. Percentage change is always relative to the starting value, so the direction matters.

Compounding decreases catches people the same way. Two successive 50% discounts do not make the item free; they make it 25% of the original price, since the second discount applies to the already-reduced amount. A 20% rise followed by a 20% fall leaves you at 96% of where you started, not 100%.

Percentage points are a separate unit and confusing them is a genuine error, not just imprecision. If an interest rate moves from 4% to 6%, that is a rise of 2 percentage points, but a 50% increase in the rate. News reports that conflate the two can overstate or understate a change by a large factor. When the quantity being measured is itself a percentage, always say which you mean.