Discount and comparison checks
Sample inputs
15% of 200 30 is what percentage of 200? Old value: 100, new value: 125 Decrease 200 by 15%
Sample results
- 15% of 200 = 30
- 30 is 15% of 200
- 100 to 125 = 25% increase
- 200 decreased by 15% = 170
Percentage Calculator
Calculate percentages, percentage change, percentage increase, and percentage decrease quickly.
Calculatorsavailable
Percentage of a Number
Find a percentage of any number, such as 15% of 200.
Result
Enter a percentage and a number to calculate the result.
What Percentage Is One Number of Another?
Work out what percentage one number is of another.
Result
Enter a part value and a whole value to calculate the percentage.
Percentage Increase or Decrease
Compare an original value with a new value and label the change.
Result
Enter an original value and a new value to calculate percentage change.
Increase or Decrease a Number
Increase or decrease a starting number by a percentage.
Action
Result
Enter a starting number and a percentage to calculate the final value.
About Percentage Calculator
Use the Percentage Calculator to answer common percentage questions without building formulas by hand. Calculate a percentage of a number, find what percentage one value is of another, compare old and new values, or increase and decrease a number by a chosen percentage.
How to use
- Choose the calculator section that matches your question.
- Enter the percentage, part, whole, original value, new value, or starting number shown by that section.
- Review the live result as you type. Blank fields stay empty until there is enough information to calculate.
- Use Increase or Decrease when adjusting a number by a percentage.
- Copy a result when you need to paste it elsewhere, or reset a section to start again.
Worked example
Features
- Calculates a percentage of a number.
- Finds what percentage one number is of another.
- Calculates percentage increase, percentage decrease, and no change.
- Increases or decreases a starting number by a chosen percentage.
- Supports decimal values and negative numbers where the calculation makes sense.
- Shows friendly messages for missing inputs or zero denominators.
- Formats results with commas and without unnecessary trailing zeros.
- Runs in the browser without requiring an account.
How it works
- To calculate X% of Y, the tool divides X by 100 and multiplies by Y.
- To find what percentage X is of Y, the tool divides X by Y and multiplies by 100.
- Percentage change compares the new value with the original value, then divides by the absolute original value.
- If the original or whole value is 0, the calculator shows a message instead of returning Infinity.
- Increase and decrease calculations multiply the starting number by 1 plus or minus the percentage as a decimal.
- Results are formatted for reading, but the calculations use the numeric values entered in the form.
Common use cases
- Checking sale discounts, markups, and final prices.
- Comparing two numbers as a percentage.
- Finding percentage growth or decline between two values.
- Calculating tax, tips, fees, or simple percentage adjustments.
- Working out report, spreadsheet, and dashboard percentage figures.
- Checking homework, budgeting, planning, and everyday number questions.
Frequently asked questions
What is a Percentage Calculator?
A Percentage Calculator helps answer common percentage questions, such as finding a percentage of a number, comparing one number with another, and calculating percentage increase or decrease.
How do I calculate X% of Y?
Use the Percentage of a Number section. Enter the percentage as X and the number as Y. For example, 15% of 200 equals 30.
How do I find what percentage one number is of another?
Use the part and whole section. The calculator divides the part value by the whole value, then multiplies by 100.
How is percentage change calculated?
Percentage change is calculated from the difference between the new value and the original value, divided by the absolute original value, then multiplied by 100.
What is the difference between percentage increase and decrease?
An increase means the new value is higher than the original value. A decrease means the new value is lower than the original value.
Can I use decimal percentages?
Yes. Decimal values are supported, so you can calculate values such as 12.5% of 200 or increase a number by 2.75%.
Can I use negative numbers?
Yes. Negative numbers are accepted where the calculation is meaningful. Percentage change is measured against the absolute size of the original value.
Why does the calculator reject a denominator of 0?
Dividing by 0 does not produce a useful percentage. When a whole value or original value is 0, ToolMetro shows a clear message instead of NaN or Infinity.
Why are trailing zeros removed from results?
Results are formatted for readability, so 15.00 is shown as 15 while useful decimal places are kept when needed.
Is my calculator input stored by ToolMetro?
No. The Percentage Calculator runs in your browser and does not require server-side processing or an account.