Percentage shortcuts
- 10% of a number: move the decimal point one place left (10% of 450 = 45).
- 5% is half of 10%; 20% is double 10%; 25% is a quarter; 50% is half.
- X% of Y = Y% of X: 8% of 50 is the same as 50% of 8 = 4.
- A rise of 20% followed by a fall of 20% leaves you 4% lower, not where you started.
How to use the Percentage Calculator tool
- Pick the calculation you need.
- Type the two numbers.
- The answer and the formula appear instantly.
Why SaralKit?
- Free forever: no "credits", no trial, no premium tier, no watermark and no daily limit.
- No account, ever: nothing to sign up for. Just open the page and use it.
- No data stored: your files and the numbers you type are processed by your own browser. We never upload, store or see them.
- Works offline: once the page has loaded, most tools keep working without internet.
- Open source: anyone can read the code on GitHub.
Frequently asked questions
How do I calculate a percentage?
Percentage = (part ÷ whole) × 100. For example, 45 out of 60 = 45 ÷ 60 × 100 = 75%.
How do I calculate percentage increase?
Percentage change = (new − old) ÷ old × 100. From 80 to 100 is a 25% increase; from 100 to 80 is a 20% decrease.
How do I calculate marks percentage?
Add the marks you got in all subjects, divide by the total maximum marks and multiply by 100. Use the "Marks" box below.
What is 20% of 500?
20 ÷ 100 × 500 = 100.