Five percentage questions, answered as you type
Discounts, tips, grades, growth rates and interest all come down to the same few questions about percent. This page has one card for each: the percentage of a number, what percent one number is of another, the percentage change between two values, an increase or decrease by a percent, and the number that a given part belongs to. Every card shows its result while you type.
Use the calculator in five steps
- Pick the card that matches your question, for example Percentage change to compare last year with this year.
- Type the two numbers. Decimals work with a point or a comma, and spaces inside large numbers are fine.
- Read the result under the fields. It changes with every key you press.
- Press Copy result to put the sentence on the clipboard.
- Change a number to try another case. The five cards are independent, so each keeps its own inputs.
The formulas behind the results
The percentage of a number is the number times the percent divided by 100. The share of a part in a whole is part divided by whole, times 100. The percentage change is end minus start, divided by the absolute start value, times 100. An increase multiplies by one plus the percent over 100, a decrease by one minus it. The whole behind a part is the part times 100 divided by the percent.
Percent versus percentage points
A rate that moves from 4 % to 6 % has risen by 2 percentage points, but by 50 % in relative terms. The change card gives the relative figure; subtract the two rates yourself for points. Percentages also do not simply add up: a rise of 10 % followed by a fall of 10 % leaves you 1 % below where you started.
Limits and what stays on your device
The numbers are ordinary 64-bit floating-point values, rounded to six decimal places for display. A start value of zero has no percentage change, and a percent of zero has no whole, so the card says so instead of showing infinity. Nothing you type leaves your browser.