Percentage Calculator
Calculate percentages of values, percentage increase and decrease, or find what percent one number is of another with instant mathematical precision.
About the Percentage Calculator
The Percentage Calculator is a versatile online tool designed for students, shoppers, accountants, and analysts who need fast, error-free percentage computations. Percentages represent fractions of 100 and form the backbone of everyday quantitative tasks—from calculating sales discounts and retail markups to analyzing financial investment returns and exam test scores.
This tool supports four essential calculation modes: finding a percentage of a total, calculating what percentage one number represents of another, computing the percentage increase or decrease between two numbers, and determining the relative percentage difference between two independent values.
How to Calculate Percentage
Select the percentage calculation mode matching your question (e.g., "What is X% of Y" or "Percentage Change").
Enter your known numerical values into the provided input fields.
View the real-time calculated result, formatted formula, and fractional breakdown below.
Use the Copy button to quickly export your result or Reset to perform a new calculation.
Standard Percentage Formulas
Percentage = (Part / Whole) × 100 Percentage of Value = (Percent / 100) × Total Percentage Change = ((New Value - Old Value) / |Old Value|) × 100
To compute what fraction of a whole a quantity represents, divide the part by the total and multiply by 100. For percentage changes, divide the absolute increase or decrease by the baseline starting value.
Variable Descriptions
- Part
- The portion or subset value being evaluated
- Whole
- The base or total reference quantity
- Old Value
- The original baseline quantity before change
- New Value
- The updated quantity after change
Worked Example
Important Considerations & Tips
- Percentage change always divides by the original starting number, not the final number.
- A percentage increase followed by an equivalent percentage decrease does not return to the original value (e.g., +50% then -50% yields 75% of baseline).
- To convert a decimal to a percentage, multiply by 100 (e.g., 0.85 = 85%). To convert a percentage to a decimal, divide by 100.
Frequently Asked Questions
How do I calculate a percentage of a number?
To calculate a percentage of a number, convert the percentage into a decimal by dividing it by 100, then multiply that decimal by the total number. For example, 20% of 150 is (20 / 100) × 150 = 30.
How do I calculate percentage increase between two numbers?
Subtract the original value from the new value to find the difference. Then divide that difference by the original value and multiply by 100. For instance, from 50 to 75: (75 - 50) / 50 = 25 / 50 = 0.50 × 100 = 50% increase.
What is the difference between percentage change and percentage difference?
Percentage change is used when there is an "old" and "new" value over time, dividing by the initial value. Percentage difference is used when comparing two concurrent values where neither is the benchmark, dividing the absolute difference by their average.
Can percentage change be negative?
Yes. If the final value is smaller than the initial value, the percentage change is negative, representing a percentage decrease.
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