Percentage Calculator Calculate percentages, percentage change, and what percent one number is of another.
Percentage Calculator
Calculate percentages, percentage change, and what percent one number is of another.
Choose Calculation Mode
Select whether you want to find X% of Y, calculate percentage change, or determine what percent one number is of another.
Enter Your Numbers
Type in the values for your chosen calculation mode in the input fields provided.
View Instant Results
See the calculated percentage, the formula used, and the step-by-step breakdown immediately.
What Is Percentage Calculator?
A percentage calculator is an essential mathematical tool that performs three fundamental percentage operations. First, it calculates what a given percentage of a number equals — for example, finding that 15% of 200 is 30. Second, it determines the percentage change between two values, which is crucial for tracking growth, decline, or fluctuation in data like stock prices, sales figures, or test scores. Third, it figures out what percentage one number represents of another, answering questions like "45 is what percent of 180?" Percentages are used everywhere in daily life, from calculating tips and discounts to understanding interest rates and statistical data. This calculator handles all three scenarios with real-time results, displays the mathematical formula used, and works with decimals and negative numbers. Whether you're a student solving homework problems, a shopper figuring out sale prices, or a professional analyzing data trends, this tool delivers instant, accurate percentage calculations without the mental math.
Why Use Percentage Calculator?
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Instantly calculate three types of percentage problems in one tool
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See the mathematical formula alongside results for learning
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Handles decimals, negative numbers, and large values accurately
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No signup or installation required — works directly in your browser
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Mobile-friendly design for quick calculations on the go
Common Use Cases
Shopping & Discounts
Calculate how much you save with percentage-off deals, or figure out the final price after a discount.
Grade Calculations
Determine what percentage score you achieved on a test by dividing your points by total possible points.
Financial Analysis
Track percentage changes in stock prices, revenue, expenses, or any financial metric over time.
Tip Calculations
Quickly figure out the right tip amount by calculating a percentage of your restaurant bill.
Data Comparison
Express the relationship between two numbers as a percentage for clearer comparison and reporting.
Technical Guide
Percentage calculations are based on the concept that "percent" means "per hundred." The three core formulas are: (1) X% of Y = (X/100) × Y, which scales Y by the fraction X/100. (2) Percentage change = ((New − Old) / |Old|) × 100, which measures relative change and can be positive (increase) or negative (decrease). The absolute value in the denominator ensures correct sign handling when the old value is negative. (3) What percent is X of Y = (X / Y) × 100, which expresses X as a fraction of Y in percentage form. Important edge cases include division by zero when the denominator is zero, which this calculator flags as an error. For percentage change, a starting value of zero is mathematically undefined, so the tool reports this clearly. The calculator supports floating-point arithmetic for precise decimal results and displays up to 6 decimal places when needed. Percentage change is particularly useful in finance, where compound percentage changes over multiple periods don't simply add up — a 50% increase followed by a 50% decrease results in a net 25% decrease, not zero.
Tips & Best Practices
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1For percentage change, always use the OLD value as your base — order matters
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2Remember that a 50% increase followed by a 50% decrease does NOT return to the original
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3Use percentage change for comparing growth rates across different-sized datasets
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4To reverse a percentage calculation: if X% of Y = Z, then Y = Z / (X/100)
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5For compound changes, multiply the growth factors: 1.10 × 1.20 = 1.32 (not 30% but 32%)
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🔢 Math & CalculatorsFrequently Asked Questions
Q How do I calculate the percentage of a number?
Q What is the difference between percentage and percentage points?
Q How do I calculate percentage change?
Q Can I use this for negative numbers?
Q How is percentage change different from percentage difference?
Q What does it mean when percentage change is over 100%?
About This Tool
Percentage Calculator is a free online tool by FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration or installation required.