Percentage Calculator
Calculate percentages, percentage change, and percentage of a number, all in one place.
What is X% of a number?
X is what percent of Y?
Percentage change from X to Y
Add or subtract a percentage
ToolsSoup's Percentage Calculator is a free online tool that handles every common percentage question in one place. Work out what X% of a number is, find out what percent one value is of another, calculate the percentage increase or decrease between two numbers, and add or subtract a percentage from a starting value. Results update instantly as you type, with no rounding surprises. Everything runs in your browser — no uploads, no sign-up, and your numbers never leave your device.
What is a percentage calculator?
A percentage calculator is a tool that solves percentage problems for you so you do not have to remember the formulas. A percentage is simply a fraction out of 100, so 25% means 25 out of every 100. This calculator covers the four questions people ask most: what is X% of a number, what percent one value is of another, how much a value changed in percentage terms, and what you get after adding or subtracting a percentage. It is handy for discounts, tips, taxes, grades, statistics, and everyday math.
How to calculate a percentage
Pick the calculation that matches your question and fill in the two numbers — the answer appears right away:
- To find a percentage of a number, enter the percent and the number in the first card (for example, 20% of 150 = 30).
- To find what percent one number is of another, enter the part and the whole in the second card (for example, 30 is 20% of 150).
- To find percentage change, enter the starting value and the ending value in the third card, or add and subtract a percentage with the fourth card.
How is percentage change calculated?
Percentage change measures how much a value grew or shrank relative to where it started. The formula is the new value minus the old value, divided by the absolute starting value, multiplied by 100. If the result is positive it is a percentage increase, and if it is negative it is a percentage decrease. For example, going from 80 to 100 is a 25% increase, while going from 100 to 80 is a 20% decrease — the same gap produces different percentages because the starting point is different.
Common percentage formulas
Behind the scenes this tool uses the standard formulas: percentage of a number is (percent ÷ 100) × number; one number as a percent of another is (part ÷ whole) × 100; percentage change is ((new − old) ÷ |old|) × 100; and adding a percentage is value + (value × percent ÷ 100). Knowing the formulas is useful, but the calculator applies them for you and keeps full precision so your results stay accurate.
Why use this percentage calculator?
- Four calculators in one: percent of a number, percent of a total, percentage change, and add or subtract a percentage.
- Results update live as you type — there is no calculate button to press.
- Keeps full precision and only trims trailing rounding noise, so answers stay accurate.
- Runs entirely in your browser — your numbers are never uploaded to a server.
- 100% free with no ads, sign-up, or usage limits, and a one-click clear to start over.
Frequently asked questions
How do I calculate the percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 20% of 150 is (20 ÷ 100) × 150 = 30. Use the first card in this calculator to do it instantly — just enter the percent and the number.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 30 out of 150 is (30 ÷ 150) × 100 = 20%. The second card handles this automatically when you enter the two values.
What is the difference between percentage increase and percentage change?
Percentage change is the general term for how much a value moved relative to its starting point; when the result is positive it is called a percentage increase, and when it is negative it is a percentage decrease. This calculator shows the size of the change and labels it as an increase or a decrease for you.
How do I add or subtract a percentage from a value?
To add a percentage, take the value plus (value × percent ÷ 100); to subtract, use a negative percent. For example, 200 plus 10% is 220, and 200 minus 10% (enter −10) is 180. The fourth card does this in one step.
Are my numbers private?
Yes. All calculations happen locally in your browser using JavaScript, so the numbers you enter are never sent to or stored on any server.