Percentage Calculator
Three quick modes: find X% of a number, work out what percentage one number is of another, and measure the percentage increase or decrease between two values.
What do percentages actually mean?
A percentage is simply a fraction of 100 — "per cent" literally means "per hundred". Saying 15% is the same as saying 15 out of every 100, or the decimal 0.15. Because so many everyday numbers are expressed this way — discounts, taxes, marks, profit margins, bank rates — being fluent in the three basic percentage operations saves you constant mental arithmetic.
How to use this calculator
The tool has three independent modes; each one recalculates as you type.
- X% of Y — the classic "how much is the discount" question.
- X is what % of Y — turn a ratio into a percentage, e.g. marks scored out of total marks.
- Change from X to Y — how much a value grew or fell in percentage terms, e.g. a price rise or salary increase.
The formulas
X as % of Y = (X ÷ Y) × 100
Change % = ((Y − X) ÷ X) × 100
Worked example
A shop in Karachi offers 15% off a jacket priced at PKR 2,400. Mode 1: 15% of 2,400 = (15 ÷ 100) × 2,400 = PKR 360 off, so you pay PKR 2,040. Later, the shopkeeper says the jacket's price rose from PKR 200 to PKR 250 per metre of fabric — mode 3 tells you that is ((250 − 200) ÷ 200) × 100 = a 25% increase. And if you scored 45 marks out of 180 on a test, mode 2 shows that is (45 ÷ 180) × 100 = 25%.
When is this useful?
Daily, honestly: checking a discount is what the poster claims, computing GST or sales tax on a bill, comparing two electricity bills, working out what percentage of your salary goes to rent, converting test scores, or measuring how much a stock or the dollar rate moved. One subtlety worth remembering: percentage points and percent are different — going from 10% to 12% is a rise of 2 percentage points but a 20% relative increase. This tool computes the relative change.
Percentages also underpin our other tools — the tax calculator applies slab percentages, and the compound interest tool applies a percentage repeatedly.
Frequently asked questions
Why does the tool show 'decrease' with a positive number?
For readability the tool shows the size of the change and labels its direction, e.g. '20% decrease' rather than '−20%'. The underlying maths uses the signed formula ((Y − X) ÷ X) × 100.
What is the difference between percent and percentage points?
If a tax rate moves from 10% to 12%, it rose by 2 percentage points, but by 20% in relative terms (2 is 20% of 10). News headlines often mix these up — this tool computes relative percentage change.
How do I add a percentage to a number (e.g. 17% GST)?
Find X% of Y in mode 1, then add it to Y. For 17% GST on PKR 1,000: 17% of 1,000 = 170, total PKR 1,170. Equivalently, multiply Y by 1.17.
Why is percentage change from 200 to 250 not the same as from 250 to 200?
Because the change is measured relative to the starting value. Going up from 200 (+50 on a base of 200) is +25%; coming down from 250 (−50 on a base of 250) is −20%. The base changes, so the percentages differ.