GetPercentConvert
    Knowledge Base

    Percentage Formulas & Learning Hub

    Everything you need to understand and calculate percentages — from basics to advanced real-world applications.

    1What is a Percentage?

    The term percentage comes from the Latin per centum, which literally translates to "by the hundred." In mathematics, a percentage is a number or ratio expressed as a fraction of 100.

    Percentages are a way to describe parts of a whole where the whole is always 100. For example, 50% means 50 out of 100, or exactly half.

    • Symbolized by the % sign
    • Easily comparable to other values
    • Standard for finance, science, and math
    FractionDecimalPercent
    1 / 11.0100%
    1 / 20.550%
    1 / 40.2525%
    1 / 100.110%

    2Core Percentage Formulas

    Master these seven essential formulas to handle any percentage-related calculation you'll encounter in daily life.

    Percent of a Number

    (P / 100) × N

    Find what a certain percentage of a number is.

    Example:What is 20% of 150? (20 / 100) × 150 = 30
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    What Percent Is X of Y?

    (Part / Whole) × 100

    Find what percentage one number is of another.

    Example:12 is what percent of 60? (12 / 60) × 100 = 20%
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    Percentage Change

    ((New − Old) / |Old|) × 100

    Calculate the relative change between two values.

    Example:From 100 to 150: ((150 - 100) / 100) × 100 = 50%
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    Percentage Increase

    Original × (1 + P/100)

    Add a percentage to a starting value.

    Example:100 increased by 15%: 100 × (1 + 0.15) = 115
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    Percentage Difference

    |A − B| / ((A + B) / 2) × 100

    Compare two numbers relative to their average.

    Example:Difference between 10 and 20: |10-20|/15 × 100 = 66.67%
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    Percentage Error

    |Exp − Theo| / |Theo| × 100

    Find the precision of a measurement.

    Example:Exp 9.5 vs Theo 10.0: |9.5-10|/10 × 100 = 5%
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    Reverse Percentage

    Value / (P / 100)

    Find the original whole if you know the part and percent.

    Example:40 is 20% of what? 40 / 0.20 = 200
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    3Real-World Applications

    Where we use percentages every day.

    Shopping & Discounts

    Calculating sales tax, comparing discount prices (e.g., '20% off'), and understanding markups.

    Finance & Investing

    Tracking stock market gains, calculating annual returns, and understanding interest rates on loans.

    Science & Research

    Measuring percentage error in lab results, data analysis, and chemical concentrations.

    Education & Grades

    Converting test scores into letter grades and calculating weighted averages for GPAs.

    Health & Fitness

    Reading nutrition labels, tracking body fat percentage, and monitoring heart rate zones.

    4Percent Change vs. Percent Difference

    A common point of confusion is knowing when to use change vs. difference. They serve two very different purposes.

    Percent Change

    Sequential Time

    Used when comparing the same thing at two different times. It has a clear direction (increase or decrease).

    • Stock price growth
    • Weight loss/gain
    Percent Difference

    Side-by-Side Comparison

    Used when comparing two different things that are similar. There is no "original" value, so we use the average.

    • Comparing two laptops
    • Comparing company sizes
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