Percentage Calculator
Find a percent of a number, work out what percent one number is of another, or measure percentage increase or decrease — instantly and privately. Choose the mode, enter your two values, and the calculator returns the result plus the exact formula it used. Perfect for grades, discounts, markups and quick maths, with nothing uploaded.
What is a percentage?
A percentage is a way of expressing a number as a fraction of 100. The % symbol means 'per hundred', so 25% is simply 25 out of every 100. Percentages make comparisons easy because they scale different-sized quantities onto one common base, which is why they appear everywhere — from exam marks and test scores to interest rates, discounts, tax and growth figures. There are three everyday questions a percentage answers: what X% of a number is, what percent one number is of another, and how much a value has changed from one point to another. This calculator handles all three in one place and shows the formula behind each result. Understanding percentages also helps you judge whether a change is a rise or a fall, and how big that change really is relative to the starting value.
Example
What is 15% of 200? The calculator returns 30, because 200 × 15 ÷ 100 = 30. Switch the mode to 'X is what % of Y' and enter 40 and 200 — it returns 20%. Use the change mode for a price moving from 80 to 100 and you get a 25% increase.
Who is this percentage calculator for?
A percentage calculator finds a percent of a number, works out what percent one number is of another, or measures a percentage increase or decrease. Students and educators use it constantly.
- Students: work out exam and marks percentages for a report card, or check how much a single test contributes to your grade.
- Teachers: set mark schemes, scale a test and convert raw class scores to percentages.
- College learners: figure out discounts, markups and percentage changes quickly for coursework and everyday sums.
Percentage chart
Here is how a few common percentages apply to a base figure using the percentage formula (X ÷ 100) × Y:
| Percentage | Fraction | Of 200 | Of 350 |
|---|---|---|---|
| 10% | 1/10 | 20.00 | 35.00 |
| 20% | 1/5 | 40.00 | 70.00 |
| 25% | 1/4 | 50.00 | 87.50 |
| 50% | 1/2 | 100.00 | 175.00 |
| 75% | 3/4 | 150.00 | 262.50 |
| 100% | 1 | 200.00 | 350.00 |
Common use cases
- Working out an exam or marks percentage for a report card.
- Adding a margin or markup to a selling price.
- Comparing a sale discount across two shops.
- Measuring a pay rise or fall as a percentage.
Pro tips
- Find the original before a percentage change by dividing the new value by (1 + percent ÷ 100).
- Percentage change is relative to the starting value, so the same move is a bigger percent on a small base.
- Round money to two decimals, but keep more decimals for precise scientific work.
How to use
- Pick the kind of calculation you need.
- Enter your two values.
- Click Calculate to see the result and the formula behind it.
Percentage formulas
X% of Y = (X / 100) × Y X is what % of Y = (X / Y) × 100 % change X→Y = ((Y − X) / X) × 100
Percentage Calculator FAQs
How do I find what X% of Y is?
Multiply Y by X and divide by 100. For example, 15% of 200 is 200 × 15 ÷ 100 = 30.
How do I calculate percentage increase?
Subtract the original value from the new value, divide by the original and multiply by 100. A move from 80 to 100 is a 25% increase.
How do I calculate percentage decrease?
Use the same change formula: ((new − original) ÷ original) × 100. A drop from 100 to 80 is a 20% decrease.
What is the formula for a percentage?
Percentage = (part ÷ whole) × 100. It expresses a part of a whole as a number out of 100.
How do I find what percent one number is of another?
Divide the first number by the second and multiply by 100. So 40 is 20% of 200.
How do I calculate the percentage of marks?
Percentage of marks = (marks obtained ÷ total marks) × 100. So 419 out of 500 is 83.8%.
What is the difference between percentage change and percentage points?
Percentage change is relative growth, while percentage points are the absolute gap. A move from 10% to 15% is a 50% relative increase but only 5 points.
How do I convert a fraction to a percentage?
Divide the numerator by the denominator and multiply by 100. So 3/4 = 0.75 × 100 = 75%.
How do I find the original value before a percentage increase?
Divide the new value by (1 + percent ÷ 100). A value of 115 after a 15% increase is 115 ÷ 1.15 = 100.
Is this percentage calculator free and private?
Yes. It is free, runs entirely in your browser, and no data is uploaded.
More FAQs
Are these calculators free to use?
Yes, every calculator is completely free, with no signup and no limits.
Do I need an account or install anything?
No. Everything runs in your browser — no install, no account.
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