Percentage Calculator
Work out any percentage instantly — three calculators in one.
Use this percentage calculator to solve the three questions people ask most: “what is X% of a number?”, “X is what percent of Y?”, and “what is the percentage increase or decrease from one value to another?” Results update the instant you type — there's no Calculate button to press.
Every calculation runs entirely in your browser, so the numbers you enter never leave your device. Each answer comes with the exact formula and a worked example, so you can check the math yourself.
📖 Read the guide: How to Calculate Percentages: A Complete Guide
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Formula
What is X% of Y
(X ÷ 100) × Y = result
Convert the percentage to a decimal by dividing by 100, then multiply by the number. Example: 25% of 200 → (25 ÷ 100) × 200 = 50.
X is what percent of Y
(X ÷ Y) × 100 = result %
Divide the part by the whole, then multiply by 100. Example: 50 is what percent of 200 → (50 ÷ 200) × 100 = 25%.
Percentage change from X to Y
((Y − X) ÷ X) × 100 = change %
Subtract the old value from the new value, divide by the old value, then multiply by 100. A positive result is an increase, a negative result is a decrease. Example: 200 → 250 = +25%.
How to use the percentage calculator
- 1Pick the question that matches what you need: “% of a number”, “is what percent of”, or “increase / decrease”.
- 2Type your numbers into the two fields. The answer appears immediately, with the formula filled in.
- 3Use the Copy button to grab the result, or share the page URL — your inputs are saved in the link so others see the same calculation.
Examples
| Example | Input | Result |
|---|---|---|
| Percent of a number | 25% of 200 | 50 |
| Is what percent of | 50 of 200 | 25% |
| Increase | 200 → 250 | +25% |
| Decrease | 250 → 200 | −20% |
What is a percentage?
A percentage is a way of expressing a number as a fraction of 100. The word comes from the Latin “per centum”, meaning “per hundred”. When we say 25%, we mean 25 out of every 100, or the fraction 25/100, or the decimal 0.25. Percentages let us compare quantities on a common scale, which is why they show up everywhere from shop discounts and tips to interest rates, test scores, and statistics.
Because a percentage is just a scaled fraction, every percentage problem is really a small piece of arithmetic: convert the percent to a decimal (divide by 100), then multiply or divide as needed. This calculator does that for you and shows the working so the result is never a black box.
How to calculate a percentage by hand
To find a percentage of a number, divide the percentage by 100 and multiply by the number. For example, 20% of 80 is (20 ÷ 100) × 80 = 0.2 × 80 = 16. To find what percent one number is of another, divide the first by the second and multiply by 100: 30 out of 120 is (30 ÷ 120) × 100 = 25%.
To find a percentage increase or decrease, take the difference between the two values, divide by the original value, and multiply by 100. Going from 50 to 75 is an increase of (75 − 50) ÷ 50 × 100 = 50%. Going from 75 to 50 is a decrease of (50 − 75) ÷ 75 × 100 ≈ −33.3%. Notice the percentages differ depending on which value you start from — that asymmetry trips a lot of people up.
Everyday uses
Percentages power day-to-day decisions: a 30%-off sale, an 18% restaurant tip, a 7.5% sales tax, a 5% raise, or the share of a budget spent on rent. They also describe change over time — revenue up 12% year over year, a portfolio down 4% this quarter. Getting the direction and the base value right matters: “20% more” and “20% less” do not cancel out, and a percentage change always depends on what you measured from.
This calculator provides results for general and educational purposes. For important financial or academic decisions, double-check critical calculations independently.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 to turn it into a decimal, then multiply by the number. For example, 15% of 60 is (15 ÷ 100) × 60 = 9. The “% of a number” tab above does this for you instantly.
How do I find what percentage one number is of another?
Divide the first number (the part) by the second number (the whole) and multiply by 100. For example, 45 out of 180 is (45 ÷ 180) × 100 = 25%. Use the “is what percent of” tab.
How do I calculate percentage increase or decrease?
Subtract the original value from the new value, divide by the original value, and multiply by 100. A positive answer is an increase; a negative answer is a decrease. From 80 to 100 is +25%; from 100 to 80 is −20%.
Why aren't a percentage increase and decrease the same size?
Because each is measured from a different starting value. Going from 100 to 120 is +20% (20 out of 100), but going back from 120 to 100 is only −16.7% (20 out of 120). The base changes, so the percentages differ.
Does this calculator store the numbers I enter?
No. All calculations run in your browser — nothing you type is uploaded, logged, or stored on a server. Your data never leaves your device.
Embed this calculator
Add the Percentage Calculator to your own website — free. Copy and paste this snippet:
<iframe src="https://numvella.com/embed/percentage-calculator" width="100%" height="460" style="border:1px solid #e2e8f0;border-radius:12px" title="Percentage Calculator — Numvella" loading="lazy"></iframe>Related calculators
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