Percentage math
Percentage Calculator for Fast Comparisons
A percentage calculator is useful when the important question is not just the number itself, but how that number relates to another value. This calculator covers the common percentage tasks people need for prices, growth, discounts, ratios, and quick comparisons.
Use percent of when you need a portion of a total, percent ratio when you want to express one value as a share of another, and percent change when the direction matters. The starting value and ending value are important for percent change because reversing them changes the result.
The add percent and subtract percent modes are built for adjustments to a base value, such as increasing a price by a rate or reducing an amount by a discount. Keeping these as separate modes makes the calculation easier to check than typing a formula from memory.
It is also worth separating percentages from percentage points. Moving from 5% to 7% is a change of 2 percentage points, but it is a 40% increase relative to the starting rate. A clear calculator helps avoid that kind of mistake.
Like the simple calculator, this page uses decimal arithmetic for cleaner results. That matters when percentages are applied to money, measurements, rates, or any value where small rounding errors can make the answer harder to trust.