The three most common percentage questions, each on its own line: take a percentage of a number, find what percent one value is of another, and measure how much something grew or dropped. Change any field and the result updates immediately.
How it works
A percentage is just a fraction with 100 in the denominator, so every calculation here is one multiplication or division. “20% of 150” multiplies 150 by 0.20 to get 30. “30 is what percent of 150” divides 30 by 150 and multiplies by 100 to get 20%.
Percentage change compares a new value against the starting value: the difference divided by where you started. Going from 100 to 125 is +25%, but going back from 125 to 100 is −20% — the direction matters because the base changes. This asymmetry trips people up more than anything else about percentages.
Results are rounded to four decimal places, which is precise enough for money, grades and statistics while avoiding the long floating-point tails computers produce internally.
Practical examples
Discount at the register
A jacket costs 4,800 dinars with a 35% discount. 35% of 4,800 is 1,680 — so you pay 3,120. Type 35 and 4800 into the first row to verify it before you reach the register.
Test score to percentage
You scored 43 out of 60 points. The second row: 43 is 71.67% of 60. Useful for converting any points-based score into a percentage grade.
Salary raise
Your pay went from 95,000 to 104,500. The third row shows a +10% change. Works in reverse for price drops — from 104,500 back to 95,000 is −9.09%, not −10%.
Portion of a budget
Marketing gets 12% of a €40,000 budget: the first row gives €4,800. Change the percentage to instantly compare scenarios.
Frequently asked questions
How do I calculate a percentage of a number by hand?
Divide the percentage by 100 and multiply: 18% of 250 is 0.18 × 250 = 45. For quick mental math, find 10% first (move the decimal point) and scale: 10% of 250 is 25, so 20% is 50, and 18% is 50 minus a fifth of 25.
Why is a 25% increase not undone by a 25% decrease?
Because the base changes. 100 increased by 25% is 125, but 25% of 125 is 31.25, so decreasing 125 by 25% gives 93.75, not 100. To undo a 25% increase you need a 20% decrease.
What is the difference between percentage points and percent?
If an interest rate moves from 4% to 6%, it rose by 2 percentage points but by 50 percent (2 is half of 4). News reports often mix these up; this calculator returns percent, the relative measure.
Can the result be more than 100%?
Yes. 300 is 200% of 150, and growth from 50 to 200 is a +300% change. Percentages above 100 simply mean “more than the whole you compared against”.
What happens when I divide by zero?
Asking “what percent is X of 0” or “change from 0 to X” has no defined answer, so the calculator shows a dash instead of a misleading number.
How do I calculate a reverse percentage — the price before a discount?
If something costs 60 after a 25% discount, it was 60 ÷ 0.75 = 80. In this calculator you can verify with the first row: 25% of 80 is 20, and 80 − 20 = 60.
How do I add a percentage on top, like VAT?
Compute the percentage in the first row and add it to the base: 20% VAT on 1,000 is 200, total 1,200. Or multiply by 1.20 directly. A dedicated VAT calculator with net/gross fields is on this site’s roadmap.
Does the calculator work with negative numbers?
Yes. 50% of −80 is −40, and change from −10 to −5 is +50% (it moved halfway toward zero). Negative bases in percentage change can be counterintuitive, so double-check what your numbers represent.
How precise are the results?
Up to four decimal places, with trailing zeros removed. Internally the math is standard 64-bit floating point — the same precision spreadsheets use.
Can I use decimals or commas in the fields?
Use a dot as the decimal separator (12.5, not 12,5) — that is what the number fields accept in every browser regardless of your system language.
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