Percentage Calculator
Calculate percentages, percentage increases and decreases, relative portions, and percentage differences with step-by-step formulas.
Formula: (15 / 100) × 250 = 37.5
How Percentages Work & Fundamental Formulas
A percentage represents a dimensionless ratio expressed as a fraction of 100 (from the Latin 'per centum' meaning 'by the hundred'). Percentages allow straightforward comparisons of proportions, growth rates, discounts, and statistical changes across disparate data sets.
Formula Quick-Sheet
Practical Everyday Uses
- ✓Retail Discounts & Sale Markdowns
Determine the exact dollar savings when a clothing store or electronics retailer advertises 25% or 40% off.
- ✓Financial Growth & Stock Market Returns
Calculate the percentage gain or loss between your initial investment purchase price and current market portfolio valuation.
- ✓Salary Raises & Cost of Living Adjustments (COLA)
Evaluate annual compensation adjustments to see how a $5,000 raise translates into a percentage increase.
- ✓Academic Grades & Exam Scoring
Convert raw test marks into standard 100-point grade percentages effortlessly.
Why Use This Percentage Tool
4 Calculation Modes in One
Calculates X% of Y, X is what % of Y, percentage increase/decrease, and percentage difference between two values.
Step-by-Step Mathematical Formulas
Shows the exact arithmetic equation so you understand how the final percentage was derived.
Handles Decimals & Negative Values
Supports precise fractional percentages (e.g. 3.75%) and negative values for accurate financial modeling.
Instant One-Click Copy
Copy your calculated answers directly to your clipboard for emails, spreadsheets, or homework.
Frequently Asked Questions
How do you calculate the percentage of a number?
To find P percent of a number X, convert the percentage into a decimal by dividing by 100, then multiply by X: Result = (P / 100) * X. For example, 15% of 250 = 0.15 * 250 = 37.5.
How do you calculate percentage increase or decrease?
To calculate percentage change from an old value to a new value: Percentage Change = [(New Value - Old Value) / Old Value] * 100. If the answer is positive, it represents a percentage increase; if negative, it is a percentage decrease.
What is the difference between percentage change and percentage difference?
Percentage change compares a final value to a specific starting base value (directional). Percentage difference compares two arbitrary numbers where neither is considered the 'original' base; it divides the absolute difference by the average of the two numbers: |A - B| / ((A + B) / 2) * 100.
How do you calculate what percentage one number is of another?
Divide the part by the whole and multiply by 100: (Part / Whole) * 100. For instance, to find what percent 45 is of 180: (45 / 180) * 100 = 0.25 * 100 = 25%.
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