Percentage Calculator
Calculate percentages, percentage change, and percentage of a number with simple formulas and instant results.
Percentage of a Number
- Result = Number × Percentage / 100
Percentage Change
- Change % = (New − Old) ÷ Old × 100
20% of 150 is 30 because 150 × 20 / 100 = 30.
Select the percentage question you want answered, enter the two values, and the calculator applies the matching formula.
Use it for discounts, exam scores, growth rates, tax, comparisons, and everyday percentage calculations.
The most common mistake is reversing the first and second values in percentage change questions.
Examples
Example 1: Percent of Number
20% of 150
150 × 20 / 100
Example 2: What Percent?
30 is what percent of 150?
30 ÷ 150 × 100
Example 3: Percentage Change
Old value: 100
New value: 125
When to Use This Calculator
- Find discounts and sale reductions
- Calculate exam or test scores
- Measure increases or decreases
- Compare two numbers quickly
- Work out tax or commission rates
How It Works
- Choose the calculation type.
- Enter the values requested by the labels.
- Click Calculate to get the percentage result and formula.
Common Mistakes
- Swapping old and new values in percentage change
- Forgetting to divide by 100
- Confusing percentage points with percent change
- Rounding too early
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Frequently Asked Questions
What can this percentage calculator do?
It can calculate a percentage of a number, what percent one number is of another, and percentage increase or decrease.
How do I calculate 20% of a number?
Multiply the number by 20 and divide by 100.
What is percentage change?
Percentage change compares an old value to a new value as a percentage of the old value.
Can I use decimals?
Yes. You can enter decimal values for more precise calculations.