About this Percentage Calculator
Percentages are everywhere, from shopping discounts to tax rates. This calculator handles the three most common percentage problems: finding a percentage of a number, finding what percentage one number is of another, and calculating the percentage change (increase/decrease) between two values.
Who this calculator is for
- Shoppers comparing discounts, markups, and sale prices.
- Students and teachers working through percent and change problems.
- Anyone checking growth or change math quickly.
When to use it
- Use this calculator to find sale prices, tips, or tax amounts.
- Use it when you need to compare a new value against an original value.
- Use it to compare how much a value increased or decreased.
How to use this calculator
- Select the Mode matching your question (e.g., 'What is X% of Y?').
- Enter the values for A and B.
- The result explains the calculation clearly.
Key assumptions
- Percentage change uses the first value as the starting point and the second value as the new value.
- Percent-of mode returns the raw percentage and shows a one-decimal explanation.
- Percentage change results are rounded to two decimal places for display.
Accuracy and testing
Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.
How this calculator works
The math depends on the mode:
1. X% of Y: (X / 100) * Y
2. X is what % of Y: (X / Y) * 100
3. Percentage Change: ((New - Old) / Old) * 100
Inputs explained
Mode
Select the specific type of percentage problem you want to solve.
Value A & B
The numbers involved in your query. Labels update based on the selected mode.
Understanding your results
Percentage change is rounded to 2 decimal places. In percent-of mode, the explanation text rounds to 1 decimal place. A positive change means an increase; a negative change means a decrease.
Example scenarios
Discount
What is 20% of $50? Result: $10.
Test Score
45 is what % of 50? Result: 90%.
Growth
Change from 100 to 150? Result: 50% Increase.
Key Features
- Instant Calculation
- Private & Secure
- Mobile Optimized
Tips & Best Practices
- To find the sale price, subtract the percentage result from the original price.
- To calculate a tip (20%), just move the decimal point left one spot (10%) and double it.
Glossary of Terms
- Percentage
- A number or ratio expressed as a fraction of 100.
- Basis Point
- One hundredth of one percent (0.01%). Used in finance.