Percentage Calculator – Percent Of & Percent Change
The three percentage sums that come up everywhere — discounts, markups, exam scores, salary changes and growth rates — each in its own box, with the answer as you type.
Percentages are simple until they are not: a 20% discount then 20% markup does not bring a price back, and a fall from 80 to 100 is a 25% rise while the trip back is only 20%. This calculator separates the three jobs people actually mean. “What is X% of Y?” handles discounts, tips, tax slices and commissions. “X is what percent of Y?” handles scores, shares and completion rates. “Percentage increase / decrease” measures change honestly against the starting value, and says so — which is why the same two numbers give different answers in each direction.
How to use it
Pick the right box — percent of a number, a number as a percent, or the change between two numbers.
Type your two numbers — results update as you type, no button to press.
Read the full answer — the headline result plus the useful extras, like what is left after X% is taken away.
What you get
Three calculators in one — X% of Y, X as a percent of Y, and percentage increase/decrease.
Live results — answers update on every keystroke.
Change measured honestly — always against the starting value, with the direction labelled increase or decrease.
Decimal-friendly — prices, scores and rates with decimals all work.
Frequently asked questions
How do I calculate a percentage increase?
Subtract the old value from the new value, divide by the old value, and multiply by 100. Going from 80 to 100 is (100 − 80) ÷ 80 = 25%. This calculator does it in the third box.
Why is a 50% loss not undone by a 50% gain?
Because the base changes: after losing 50% of 100 you have 50, and 50% of 50 is only 25, taking you to 75. You need a 100% gain on 50 to get back to 100. Percentage change is always measured against where you start.
How do I work out a discount quickly?
Use the first box: 20% of ₦15,000 is ₦3,000 off, and the calculator also shows what is left to pay — ₦12,000.