Percentage Calculator

Percentages are used everywhere in daily life — from figuring out discounts at a shopping mall, to calculating tips at a restaurant, to analyzing profit margins in business, or tracking your battery level. Our tool bundles three different percentage calculators into one page so you never have to remember the exact mathematical formula again. Each mode handles a common question: "what is X% of Y?", "X is what percent of Y?", and "what is the percentage change from X to Y?" — the three calculations that cover the vast majority of everyday percentage needs.

Understanding the formula behind each result helps you sanity-check the numbers and apply them without the tool when you need to. • Finding a percentage of a number: multiply the number by the percentage as a decimal. To find 20% of 250, calculate 250 × 0.20 = 50. • Finding what percentage one number is of another: divide the part by the whole and multiply by 100. If 45 students out of 60 passed, that is (45 / 60) × 100 = 75%. • Finding percentage change: subtract the old value from the new value, divide by the old value, and multiply by 100. If a price rose from $80 to $100, the increase is ((100 − 80) / 80) × 100 = 25%.

A frequent error is assuming that a percentage increase and a matching percentage decrease cancel out. They do not: if a $100 item goes up 10% to $110 and then drops 10%, it falls to $99, not back to $100, because the second percentage is taken from a larger base. Another pitfall is reversing a discount incorrectly. If a price after a 20% discount is $80, the original was $80 ÷ 0.80 = $100, not $80 + 20%. When in doubt, work in decimals and double-check against the calculator above. These calculations run entirely in your browser, so nothing you enter is stored or sent anywhere.