Percentage Calculator
Work out percentages, increases, decreases and percent change instantly, with results updating as you type.
What is P% of X?
Percentage Formulas & Worked Examples
| Question | Formula | Example |
|---|---|---|
| What is 15% of 200? | (P ÷ 100) × X | 0.15 × 200 = 30 |
| 42 is what percent of 60? | (X ÷ Y) × 100 | 42 ÷ 60 × 100 = 70% |
| Increase 80 by 25% | X × (1 + P ÷ 100) | 80 × 1.25 = 100 |
| Reduce 80 by 25% | X × (1 − P ÷ 100) | 80 × 0.75 = 60 |
| Change from 80 to 100 | ((New − Old) ÷ Old) × 100 | 20 ÷ 80 × 100 = +25% |
Common Percentage Calculations
How to use this tool
- Pick the type of calculation you need using the buttons at the top.
- Type your two numbers into the fields. You do not need to press anything.
- The answer appears instantly below, along with the formula and the worked-out equation.
- Switch modes at any time to run a different kind of percentage calculation.
About this tool
This free percentage calculator handles the five percentage questions people actually ask, without you needing to remember which formula goes with which. • What is P% of X? The classic case: discounts, tips, commission, tax, and interest. • X is what percent of Y? Turning a raw number into a share: test scores, progress against a target, a slice of a budget. • Increase X by P%: adding a markup, a raise, a price rise, or a growth rate. • Decrease X by P%: applying a discount, a markdown, a depreciation, or a pay cut. • Percent change from old to new: comparing two figures over time, such as month-over-month revenue or a change in weight. Every answer updates live as you type, and the tool shows you the formula and the filled-in equation alongside the result, so you can check the working or learn the method rather than just copying a number. The calculation runs entirely in your browser. Nothing you enter is sent to a server, stored or logged, which matters when the numbers are salaries, invoices, medical figures, or client data.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. To find 15% of 200: 15 ÷ 100 = 0.15, then 0.15 × 200 = 30. Use the '% of a number' mode above and it does both steps for you.
How do I find what percentage one number is of another?
Divide the part by the whole, then multiply by 100. If you scored 42 out of 60: 42 ÷ 60 = 0.7, then 0.7 × 100 = 70%. Use the 'X is what % of Y' mode.
How do I calculate percentage increase or decrease?
Subtract the original value from the new value, divide by the original value, then multiply by 100. Going from 80 to 100: (100 − 80) ÷ 80 = 0.25, so a 25% increase. A negative answer means a decrease. Use the '% change' mode.
What is the difference between percent change and percentage points?
They are not the same. If an interest rate rises from 4% to 6%, that is a rise of 2 percentage points, but a 50% increase in the rate itself. Use percentage points when comparing two percentages directly, and percent change when comparing two quantities.
How do I add a percentage to a price, like tax or a tip?
Use the 'Increase by %' mode. For a £50 bill with a 20% tip, enter 50 and 20 to get 60. To work out just the tip amount rather than the total, use the '% of a number' mode instead.
How do I work out a discount?
Use 'Decrease by %'. A $80 item with 25% off becomes 80 × (1 − 0.25) = $60. To see how much you save rather than the final price, use '% of a number': 25% of 80 = $20.
Why does increasing by 50% then decreasing by 50% not return the original number?
Because each percentage applies to a different base. Starting at 100, a 50% increase gives 150; a 50% decrease then applies to 150, not 100, removing 75 and leaving 75. Percentage changes do not cancel out.
Is this percentage calculator free?
Yes, completely free, with no signup, no login, and no usage limit. It runs entirely in your browser, so your numbers never leave your device.