How to Calculate a Percentage of a Number

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Percentage Calculator

Find a Percentage of a Number

Example: What is 20% of 150?

% of

Find the Percentage Proportion

Example: What percentage is 30 of 120?

is what % of
function calculatePercentageOf() { var perc = parseFloat(document.getElementById('perc_val_1').value); var total = parseFloat(document.getElementById('total_val_1').value); var display = document.getElementById('result_display_1'); if (isNaN(perc) || isNaN(total)) { display.innerHTML = "Please enter valid numbers."; display.style.color = "#dc3545"; return; } var result = (perc / 100) * total; display.innerHTML = perc + "% of " + total + " is " + result.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 4}); display.style.color = "#28a745"; } function calculatePercentageIs() { var part = parseFloat(document.getElementById('part_val_2').value); var total = parseFloat(document.getElementById('total_val_2').value); var display = document.getElementById('result_display_2'); if (isNaN(part) || isNaN(total) || total === 0) { display.innerHTML = "Please enter valid numbers (Total cannot be zero)."; display.style.color = "#dc3545″; return; } var result = (part / total) * 100; display.innerHTML = part + " is " + result.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 4}) + "% of " + total; display.style.color = "#28a745"; }

How to Calculate a Percentage of a Number

Understanding how to calculate percentages is a fundamental mathematical skill used in everyday life—from calculating sales tax and discounts to analyzing data trends and tip amounts at restaurants. A percentage represents a part of a whole, specifically a fraction where the denominator is always 100.

The Percentage Formula

The standard formula for finding the value of a percentage is:

Value = (Percentage / 100) × Total Number

Step-by-Step Examples

1. Finding the value (e.g., 15% of 200)

  • Step 1: Convert the percentage to a decimal by dividing by 100 (15 / 100 = 0.15).
  • Step 2: Multiply that decimal by the total number (0.15 × 200).
  • Result: 30.

2. Finding the percentage (e.g., What % is 40 of 160?)

To find what percentage one number is of another, use this formula:

Percentage = (Part / Total) × 100
  • Step 1: Divide the part by the total (40 / 160 = 0.25).
  • Step 2: Multiply by 100 (0.25 × 100).
  • Result: 25%.

Common Percentage Conversions

Percentage Decimal Fraction
10% 0.1 1/10
25% 0.25 1/4
50% 0.5 1/2
75% 0.75 3/4

Why Use This Calculator?

While manual calculation is possible, using an online percentage calculator eliminates human error and speeds up the process for complex decimals. This tool is perfect for students, business owners calculating margins, or anyone looking to verify financial figures quickly.

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