Percentage Calculator
Pick what you want to work out — the result updates live as you type.
How Percentage Calculator Works
This calculator handles the three percentage questions people run into most often: working out a percentage of a number, working out what percent one number is of another, and working out the percentage increase or decrease between two values. Switch modes with the tabs and the answer updates as you type.
Formula & Method
Each mode uses a different formula. "% of a number": result = (percentage ÷ 100) × number. "X is what % of Y": result = (X ÷ Y) × 100. "% increase/decrease": change = ((to − from) ÷ |from|) × 100, shown as an increase when positive and a decrease when negative -- dividing by the absolute value of "from" keeps the direction label correct even if "from" is itself a negative number.
Worked Example
In "% of a number" mode, 20% of 150 gives (20 ÷ 100) × 150 = 30. In "X is what % of Y" mode, asking what percent 30 is of 150 gives (30 ÷ 150) × 100 = 20%. In "% increase/decrease" mode, going from 150 to 180 gives ((180 − 150) ÷ 150) × 100 = 20% increase.
Frequently Asked Questions
- What's the difference between percentage change and percentage points?
- Percentage change (what this calculator's "increase/decrease" mode shows) is a relative change -- going from 150 to 180 is a 20% increase. Percentage points measure an absolute gap between two percentages instead, e.g. going from 30% to 35% is "5 percentage points," which is not the same as a 5% change.
- Why does the increase/decrease mode divide by the absolute value of "From"?
- Using the absolute value keeps the increase/decrease direction meaningful even when the starting number is negative -- without it, a negative "From" value could flip the sign of the result and mislabel an increase as a decrease, or vice versa.
- Can I enter negative numbers or decimals?
- Yes -- all three modes accept negative numbers and decimals; the calculator only requires a valid, non-empty number in each field (and a non-zero "Out of" or "From" value, since dividing by zero isn't defined).
- What happens if I divide by zero, like asking what percent something is "of 0"?
- The calculator checks for this and simply shows no result (a blank dash) rather than an error or an infinite value, since a percentage "of zero" or a "change from zero" isn't mathematically defined.