Percentage Calculator

How to use it

1. Replace the numbers in the sentence you need. Results and formulas update as you type.
2. Choose increase or decrease, then select how many decimal places to show.
3. Open More for percentage points and successive changes. Tab follows the sentence; Enter moves to the next row.

Details

A percentage expresses a share out of one hundred. To find 15% of 500, multiply 500 by 15 and divide by 100: the answer is 75. To find what percentage 1,200 is of 4,800, divide the part by the whole and multiply by 100. Reversing the two numbers changes the question and the answer.

Percentage change uses the starting value as its denominator. Going from 80 to 100 is a 25% increase, but returning from 100 to 80 is a 20% decrease. A zero starting value has no defined percentage change. Negative numbers are accepted; a negative starting value keeps its sign in the denominator, so the rate may not match the everyday meaning of increase or decrease.

To undo a discount, divide the final price by the fraction left after the discount. A 20% discount leaves 80% of the original. A 100% discount cannot be reversed to a unique original value. Successive changes multiply their factors instead of adding their rates: a 10% increase followed by a 10% decrease leaves 99% of the starting value.

Only the displayed results are rounded, with exact halves rounded away from zero and trailing zeros omitted. Intermediate steps keep their precision. Arithmetic has about 15 significant digits, so very large numbers or tiny differences can lose precision. Empty fields are not treated as zero. Undefined or out-of-range results show a dash with an explanation.