Percentage Calculator
Solve the three common percentage questions instantly: percent of, is what percent, and percent change.
About Percentage Calculator
A percentage calculator answers the everyday math questions that show up constantly in shopping, budgeting, and schoolwork: how much a percentage of a number is, what percentage one number is of another, and how much something changed by. Instead of reaching for a phone calculator and working through the arithmetic by hand, you get all three common modes in one place.
All three modes are straightforward. Percent of: value × rate ÷ 100. What percent: part ÷ whole × 100. Percent change: (new − old) ÷ old × 100. The one thing to watch is percent change from zero, which is undefined because you cannot divide by zero. Decimal rates work fine, and results round to a practical precision so they are easy to use in follow-up math.
Shoppers use it to work out tips and discounts, students check homework answers, and anyone tracking budgets or progress compares changes over time. It is also handy for validating spreadsheet formulas when a quick second opinion beats rechecking a long column of numbers.
How to Use
- Choose which calculation you need: percent of, is what percent, or percent change.
- Enter the two values.
- Read the result immediately, with the formula shown.
Example
What is 15% of 200? 30
15% of 200 = 0.15 × 200 = 30. The three modes cover most everyday percentage problems.
FAQ
How do I find what percent A is of B?
Divide A by B and multiply by 100. For example, 25 ÷ 200 × 100 = 12.5%.
How is percent change calculated?
(New - Old) ÷ Old × 100. A rise from 50 to 60 is (60-50) ÷ 50 × 100 = 20%.
Can it handle decimals?
Yes, all three modes accept decimal values and round results to a practical precision.
What is 5% as a decimal?
Move the decimal point two places left, so 5% becomes 0.05. To use a percentage in arithmetic, convert it to its decimal form by dividing by 100, then multiply or divide as needed.
How do I calculate a reverse percentage?
If 15% of a number equals 30, divide 30 by 0.15 to recover the original 200. Reverse problems ask for the whole when you know a part and the percentage share it represents.