Percentage Calculator
Perform percentage calculations instantly. Select any formula card below and type to calculate live.
Find Percentage of Value
Example: 10% of 200 = 20.00
Find Percentage of Part
Example: 25 out of 100 = 25%
Percentage Increase / Decrease
Example: 50 to 80 = +60.00% change
Increase Value by Percentage
Example: 100 + 10% = 110.00
Decrease Value by Percentage
Example: 150 - 20% = 120.00
The Mathematics of Percentages
Premise: Calculating a percentage is one of the most common daily math tasks—whether you are figuring out a 20% tip, calculating a retail discount, or determining a percentage increase in sales. However, remembering the exact algebraic formula for each scenario can be tedious.
Evidence: The core formula to find what percentage one number is of another is (Part / Whole) × 100 = Percentage. For calculating percentage change (increase or decrease), the formula is ((New Value - Original Value) / Original Value) × 100. By utilizing our online percentage calculator, these mathematical formulas are instantly executed in your browser's local memory using high-precision floating-point arithmetic.
Conclusion: Understanding the underlying math empowers you, but using a dedicated, client-side calculator ensures absolute precision without the risk of mental math errors or server-side data tracking.
How to Calculate Percentages
What is a percentage?
A percentage is a number or ratio expressed as a fraction of 100. It is commonly symbolized using the percent sign, "%". For example, 35% is equivalent to the fraction 35/100, the ratio 35:100, or the decimal value 0.35. Percentages are widely used in daily life to describe discounts, interest rates, tax rates, statistics, and proportional changes.
How to find percentage of a number
To calculate the percentage of a specific number, convert the percentage into a decimal (by dividing it by 100) and then multiply it by the total number.
Formula: Result = (Percentage ÷ 100) × Total Value
Example: To find 10% of 200, divide 10 by 100 to get 0.10, and multiply by 200: 0.10 × 200 = 20.00.
How to calculate percentage increase
To determine the percentage increase from an original value to a new value, find the difference between the two values, divide it by the original value, and multiply the result by 100.
Formula: Increase % = ((New Value - Original Value) ÷ Original Value) × 100
Example: If a product price increases from $50 to $80, the percentage increase is calculated as: ((80 - 50) ÷ 50) × 100 = (30 ÷ 50) × 100 = 0.60 × 100 = 60.00%.
How to calculate percentage decrease
To determine the percentage decrease from an original value to a new value, subtract the new value from the original value, divide that difference by the original value, and multiply by 100.
Formula: Decrease % = ((Original Value - New Value) ÷ Original Value) × 100
Example: If a product price decreases from $150 to $120, the percentage decrease is calculated as: ((150 - 120) ÷ 150) × 100 = (30 ÷ 150) × 100 = 0.20 × 100 = 20.00%.
Common percentage examples
Understanding standard percentages can help you make quick mental estimations:
- 5%: Divide the number by 20 (e.g., 5% of 200 is 10.00).
- 10%: Shift the decimal point one place to the left (e.g., 10% of 250 is 25.00).
- 15%: Find 10%, add half of that amount (e.g., 15% of 80 is 8 + 4 = 12.00).
- 20%: Divide the number by 5 (e.g., 20% of 150 is 30.00).
- 25%: Divide the number by 4 (e.g., 25% of 100 is 25.00).
- 50%: Divide the number by 2 (e.g., 50% of 90 is 45.00).