Calculate percentages instantly — find X% of a number, what percentage X is of Y, or the percentage change between two values. Free online percentage calculator.
A percentage calculator finds the numerical relationship between two values expressed as a fraction of 100. It can determine what percent one number is of another, calculate a percentage of a given amount, or find the percentage increase or decrease between two figures, without manual arithmetic.
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Percentage Calculator
Our percentage calculator provides three essential calculation modes in one convenient tool. Whether you need to find a percentage of a number, determine what percentage one number is of another, or calculate the percentage change between two values, you get instant results with no registration required.
Formulas
Finding X% of a number: multiply Y by X and divide by 100. For example, 25% of 80 = 80 × 25 / 100 = 20.
What percentage X is of Y: divide X by Y and multiply by 100. If you scored 42 out of 50, that is 42 / 50 × 100 = 84%.
Percentage change: ((New − Old) / |Old|) × 100. If a stock went from €50 to €65: ((65−50)/50) × 100 = 30% increase.
Key Distinction
This is a common source of confusion. Percentage is a relative measure, while percentage points are absolute. If an interest rate goes from 5% to 7%, it increased by 2 percentage points, but by 40% in relative terms (2/5 × 100 = 40%).
News headlines often mix these up, so understanding the distinction helps you interpret financial information correctly. Use our mortgage calculator to see the real impact of interest rate differences.
Personal Finance
A 1% difference in your mortgage rate on a €200,000 loan over 25 years costs approximately €27,000 more in total interest. If your portfolio returns 7% annually versus 5%, on €50,000 invested for 20 years that difference equals over €60,000.
At 2.5% annual inflation, €100 today will have the purchasing power of only €78 in 10 years. A 3% raise on a €2,000/month salary adds €720/year.
Common Mistakes
One of the most common errors is confusing a percentage increase with its reverse: a 50% increase from 100 gives 150, but reducing 150 by 50% gives 75, not back to 100 — because the second calculation applies 50% to a different (larger) base. This asymmetry catches people off guard in discount-then-markup or salary cut-then-raise scenarios.
Another frequent mistake is adding percentages directly when they should be compounded — a 10% pay cut followed by a 10% raise does not return you to your original salary; you end up at 99% of the starting amount, because the raise is calculated on the already-reduced figure.
Mental Math Tips
10%
Move the decimal point one place to the left. 10% of 250 = 25.
5%
Find 10% and halve it. 5% of 250 = 12.5.
25%
Divide by 4. 25% of 250 = 62.5.
50%
Divide by 2. 50% of 250 = 125.
1%
Move the decimal two places left. 1% of 250 = 2.5.
Any %
Combine the above: 15% = 10% + 5%, 30% = 3 × 10%.
To find X% of Y, multiply Y by X and divide by 100. For example, 15% of 200 = 200 × 15 / 100 = 30. Our calculator does this instantly — just enter the percentage and the number.
To find what percentage X is of Y, divide X by Y and multiply by 100. For example, 30 is what % of 200? 30 ÷ 200 × 100 = 15%. Use our 'X is what % of Y?' tab for instant results.
Percentage change = ((New - Old) / |Old|) × 100. For example, change from 100 to 150 = ((150-100)/100) × 100 = 50% increase. Change from 200 to 150 = ((150-200)/200) × 100 = -25% decrease.
A percentage is relative, while percentage points are absolute. If an interest rate goes from 5% to 7%, it increased by 2 percentage points but by 40% (2/5 × 100). This distinction is important in financial contexts.
Quick mental math tricks: 10% = move decimal one place left. 5% = half of 10%. 25% = divide by 4. 50% = divide by 2. 1% = move decimal two places left. Combine these for any percentage: 15% = 10% + 5%, 30% = 3 × 10%.
No. A 20% cut reduces your salary to 80% of the original. A 20% raise on that reduced amount brings you to 96% of the original salary (80% x 1.20 = 96%), not back to 100%. This is because percentage changes compound on the current value, not the original one.
Percentage change is a relative measure (e.g., sales grew from 100 to 110 = a 10% increase). Percentage points measure an absolute difference between two percentages (e.g., an interest rate moving from 5% to 7% is a 2 percentage point increase, which is also a 40% relative increase). Mixing these up is a very common reporting error.