How to use the percentage calculator
Step 1 — Pick the question you are asking
Ten modes across the top, each phrased as the question it answers: what is 15% of 1,200, 43 out of 50 is what percentage, what was the price before 20% tax, and so on. Choosing the right shape of question is most of the battle with percentages.
Step 2 — Type your numbers
The answer updates as you type — there is no Calculate button to press. You can paste numbers with a percent sign or thousands separators (25%, 1,200) and they will be read correctly.
Step 3 — Read the working, not just the answer
Every result shows the formula and then the same formula with your own numbers substituted in, so you can check it, learn the method, or copy it into homework or a report.
Step 4 — Take note of the caution line
Underneath each answer is the thing people get wrong about that particular calculation — that reversing a percentage change does not use the same percentage, that markup and margin are different numbers, that two discounts do not add together.
Step 5 — Set the rounding
Answers round to as many decimals as they need, up to six. If you want whole numbers or a fixed two decimal places — for money, usually — pick that from the rounding menu and every answer follows it.
Step 6 — Copy what you need
Copy answer puts the figure alone on your clipboard; Copy the working takes the sentence, the formula and the substituted calculation together. The example chips underneath fill in a worked question if you would rather start from one.
About the percentage calculator
Percentages turn up in discounts, taxes, tips, interest, exam marks, statistics and headlines — and the different shapes of percentage question trip people up constantly, because they look alike and behave differently. This calculator handles ten of them in one place, and shows the formula and the working for each rather than only the answer.
Everything happens in your browser. Nothing is uploaded, nothing is stored, and there is no sign-up or limit.
The ten questions it answers
- % of a number — what is 15% of 1,200?
- X is what % of Y — 43 out of 50 as a percentage.
- % increase or decrease — the change from one value to another.
- Add or subtract % — raise or lower a number by a percentage.
- Reverse (before tax) — a figure already includes a percentage; what was it before?
- % difference — how far apart two values are, with no direction.
- Discount — the sale price and what you save.
- Markup & margin — the selling price, and the margin that markup actually produces.
- Ratio to % — each side of 3:5 as a share of the whole.
- Marks & fractions — a score out of a total, as a percentage.
The three core calculations
| Question | Formula | Example |
|---|---|---|
| What is X% of Y? | (X ÷ 100) × Y | 15% of 200 = 30 |
| X is what percent of Y? | (X ÷ Y) × 100 | 45 of 180 = 25% |
| Percentage change | ((new − old) ÷ old) × 100 | 80 → 100 = +25% |
Percentage of a number is the most common case — a discount, a tip, a tax, a share of a total. Divide the percentage by 100 and multiply: 15% of 200 is 0.15 × 200 = 30. The same method gives a 7% sales tax on a ₹1,200 bill (₹84) or 60% of 50 marks (30).
What percentage one number is of another takes a part and a whole and gives the proportion: divide the part by the whole and multiply by 100. Scored 45 out of 180? That is (45 ÷ 180) × 100 = 25%. This is how raw counts become comparable rates.
Percentage increase and decrease divides the difference by the original value, never the new one. Going from 80 to 100 is a 25% increase, because the 20 gained is measured against the starting 80.
Why a rise and a fall of the same size are not equal
Going from 100 to 80 is a 20% decrease, because the 20 lost is measured against 100. But climbing back from 80 to 100 is a 25% increase, because the same 20 is now measured against 80. The two directions are not symmetrical, and the gap widens as the numbers get bigger: an investment that falls 50% needs to rise 100% simply to break even, and one that falls 80% needs to rise 400%.
This is the single most useful thing to understand about percentages, and it is why the change mode always tells you what the return journey would be.
Reverse percentages — the one everyone gets wrong
A bill is ₹2,499 including 18% tax. What was it before the tax? The instinct is to take 18% off ₹2,499, which gives ₹2,049.18. That is wrong, and it is wrong by a predictable amount every time.
The 18% was added to the original figure, not to the final one, so the final figure is 118% of what you are looking for. You divide rather than subtract: 2,499 ÷ 1.18 = ₹2,117.80. Check it by adding 18% back and you land on 2,499 exactly. The reverse mode does this for tax added or a discount already taken off, and shows you the wrong answer alongside the right one so the difference is obvious.
Markup is not margin
Buy at 100, mark up 40%, sell at 140. Your profit is 40 — but that 40 is 28.6% of the selling price, not 40%. Markup measures profit against cost; margin measures it against the price the customer pays. Quoting one when you mean the other is one of the most expensive mistakes in small-business pricing, and the calculator prints both figures every time so the two never get confused.
Percent versus percentage points
A percentage point is the plain difference between two percentages; a percent is a relative change. If an interest rate moves from 5% to 6%, that is a rise of one percentage point — and also a 20% increase in the rate itself. Both are true, they are wildly different numbers, and news reports mix them up constantly. Whenever you see a percentage of a percentage, check which one is meant.
Percentage change or percentage difference?
They sound interchangeable and are not. Change has a direction and a starting point: from 40 to 60 is a 50% increase, because the 20 is measured against 40. Difference compares two values of equal standing with no before or after, so it divides by their average: 40 and 60 differ by 40%, because 20 is measured against 50. Use change for a value that moved over time, and difference for two separate measurements — two shops’ prices, two lab results, two candidates’ scores.
Where this fits with the other tools
For money over time rather than a single percentage, EMI Calculator and Compound Interest Calculator do the repeated-percentage work, and Discount Calculator handles stacked and seasonal offers. GST Calculator is the tax-specific version of the reverse mode above. For marks and grades there is CGPA to Percentage, and for everything else numeric, Unit Converter and Scientific Calculator.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. 15% of 1,200 is (15 ÷ 100) × 1,200 = 180. The first mode does this and shows the working.
How do I work out what percentage one number is of another?
Divide the part by the whole and multiply by 100. 43 out of 50 is (43 ÷ 50) × 100 = 86%.
How do I calculate percentage increase?
Subtract the old value from the new one, divide by the old value, and multiply by 100. From 80 to 100: (100 − 80) ÷ 80 × 100 = 25%. Dividing by the new value instead is the most common mistake and gives 20%.
How do I remove tax or VAT from a total?
Divide, do not subtract. For 18% included in 2,499: 2,499 ÷ 1.18 = 2,117.80. Taking 18% off the total would give 2,049.18, which is about 69 too low. The Reverse mode does it correctly and shows both figures.
What is the difference between markup and margin?
Markup is profit as a percentage of what you paid; margin is profit as a percentage of what you charge. A 40% markup on a cost of 100 gives a price of 140 and a margin of 28.6%. Markup is always the bigger number.
Do two discounts add up?
No. 20% off and then a further 10% off is 28% off in total, not 30% — the second discount applies to the already-reduced price. Chain them by running the Discount mode twice.
What is the difference between percent and percentage points?
If a figure moves from 4% to 6%, that is 2 percentage points, and also a 50% increase. Points are the plain gap between two percentages; percent is the relative change between them.
Can a percentage be more than 100?
Yes, whenever the part is bigger than the whole you are comparing it to. 150 out of 100 is 150%, and a price that triples has risen 200%. The calculator handles values above 100% and negative values without complaint.
How do I turn a fraction or a ratio into a percentage?
A fraction divides the top by the bottom and multiplies by 100, so 3/5 is 60%. A ratio splits a whole between its parts, so 3:5 is 3 ÷ 8 = 37.5% against 62.5%. They are different questions, and the tool keeps them in separate modes for exactly that reason.
What percentage is my exam score?
Score divided by total, times 100. 17 out of 20 is 85%. The Marks & fractions mode also tells you roughly where that sits against typical grade boundaries — a guide only, since boundaries differ by school and country.
Is the percentage calculator free?
Yes — no account, no email, no limit. Every calculation runs in your browser, so nothing you type is sent anywhere.
