Percentage Calculator – Free Online Tool
Three instant percentage calculators in one: find X% of a number, calculate what percent X is of Y, and compute percentage change between two values — with formula display, quick presets, and copy-to-clipboard.
What Is the Percentage Calculator?
A free, instant percentage calculator that solves three types of percentage problems: finding X% of a number, determining what percent one number is of another, and computing the percentage change (increase or decrease) between two values. Results update as you type — no button to press — and every answer shows the formula used so you understand the math.
How Does the Calculator Work?
Enter your numbers and the result appears instantly. The 'X% of Y' calculator multiplies the percentage (as a decimal) by the number. The 'X is what % of Y' calculator divides the part by the whole and multiplies by 100. The 'Percentage Change' calculator subtracts the old value from the new, divides by the absolute value of the old, and multiplies by 100. All arithmetic runs client-side in your browser.
How to Use the Percentage Calculator
1. Choose your calculation type using the tab bar: '% of', 'is what %', or '% change'. 2. Enter your numbers — the result updates instantly as you type. 3. Use a quick preset (tip, tax, discount, markup) to pre-fill common values. 4. Read the formula below the result to understand the math. 5. Click Copy to copy the result to your clipboard.
Why Choose Our Percentage Calculator?
Most percentage calculators are cluttered or require pressing a button. Ours updates results in real time, shows the formula transparently, includes quick presets for everyday scenarios (15% tip, 20% discount, 8.25% tax), and lets you copy results with one click. Three calculator modes cover every common percentage problem in one clean interface.
Who Benefits from This Tool?
Students checking homework and exam scores. Shoppers calculating sale discounts. Restaurant-goers figuring tips. Business owners computing profit margins, markups, and sales tax. Investors tracking portfolio growth. Teachers grading papers. Anyone who needs quick, accurate percentage math without pulling out a calculator app.
Frequently Asked Questions
Everything you need to know about the Percentage Calculator.
How do you calculate a percentage increase?
Subtract the old value from the new value, divide by the old value, and multiply by 100. For example, going from 80 to 100: (100 - 80) / 80 × 100 = 25% increase. Our Percentage Change tab does this instantly.
Can I use this for calculating discounts and sales tax?
Yes! To find a 20% discount on $150, use the '% of' tab: 20% of 150 = 30. Subtract that from the price to get $120. For sales tax, enter your tax rate and the price to find the tax amount.
What does '% of' mean in math?
Percent means 'per hundred.' So 15% of 200 means '15 per 100 of 200' — you convert 15% to the decimal 0.15 and multiply by 200 to get 30. The formula is always: (percentage / 100) × number.
What is the difference between percentage change and percentage points?
Percentage change is relative: going from 10% to 15% is a 50% increase. Percentage points are absolute: 15% minus 10% equals 5 percentage points. Our calculator computes percentage change (the relative measure), which is the more commonly needed calculation.
Does the calculator show the formula?
Yes. Every result includes the formula used to compute it, so you can verify the math and learn the calculation method. This makes it useful for both quick answers and educational purposes.
Is this tool free and private?
Yes. All calculations happen instantly in your browser. No data is sent to any server, no sign-up is required, and there are no usage limits.