Percentage calculator
Three everyday percent questions, answered the moment you type. Find a percent of a number, turn one value into a percentage of another, or measure the change between two numbers.
Handy for tips, discounts, VAT and commission — e.g. a 20% tip on a $60 bill.
Great for scores and shares — e.g. 45 correct out of 180 questions.
Compare a before and after — prices, weights, followers, results.
How to use it
Pick your question
Switch tabs to match what you are asking: a percent of a number, one value as a percent of another, or the change between two numbers.
Type two numbers
Fill the fields in the sentence. There is no submit button — the result recalculates on every keystroke, decimals and negatives included.
Check the working
Under each answer you get the exact formula that produced it, so you can trust the figure or copy the method by hand.
Why people keep this one open
No calculate button
The number updates live as you type. That sounds small, but when you are trying five discounts in a row it saves a lot of clicking.
Stays on your screen
Every calculation happens in your browser. Nothing you enter is uploaded, logged or shared, and the page works even with the network switched off.
Handles the tricky bits
Negative changes, decimal percentages and divide-by-zero cases are all handled cleanly, with a plain-language note instead of a broken result.
Percentages without the head-scratching
A percentage is just a fraction with a fixed denominator of 100. "45 percent" literally means 45 out of every 100, which is why the word comes from the Latin per centum. Once you see it that way, most percentage questions collapse into one of three shapes.
Finding a percent of a number
Multiply the number by the percent, then divide by 100. To get 15% of 200 you calculate 200 × 15 ÷ 100 = 30. This is the maths behind tips, sales tax, discounts and interest.
Turning a ratio into a percent
Divide the part by the whole and multiply by 100. If you answered 45 of 180 questions correctly, that is 45 ÷ 180 × 100 = 25%. The same move converts grades, market share and completion rates into percentages.
Measuring a change
Subtract the old value from the new one, divide by the old value, and multiply by 100. Going from 200 to 250 is (250 − 200) ÷ 200 × 100 = 25% increase. A negative answer means a decrease. Note this differs from percentage points: moving from 40% to 50% is a 10 point rise but a 25% increase.
Common questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide the result by 100. For example, 15% of 200 is 200 × 15 ÷ 100 = 30. The first tab does this for you as you type.
How do I find what percent one number is of another?
Divide the first number by the second, then multiply by 100. So 45 out of 180 is 45 ÷ 180 × 100 = 25%. Use the "What percent" tab for this.
How is a percentage increase or decrease calculated?
Take the new value minus the old value, divide by the old value, and multiply by 100. A rise from 200 to 250 is a 25% increase; a fall to 150 would be a 25% decrease.
What is the difference between a percent and a percentage point?
Percentage points measure the gap between two percentages, while a percentage change measures the relative difference. Going from 40% to 50% is 10 percentage points, but a 25% increase.
Can I use decimals and negative numbers?
Yes. Enter values like 12.5 or -30 freely. Results round to a sensible number of decimals, and negative changes are labelled as a decrease automatically.
Is anything I type sent to a server?
No. The calculator is a single self-contained page and every figure is worked out locally in your browser. Nothing is uploaded, saved or tracked.