How to Calculate Percentage of Number

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Percentage Calculator

Quickly calculate percentages, percentage changes, and proportions.

1. Find the Percentage of a Specific Number

Example: What is 15% of 200?

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2. Find the Percentage of One Number Relative to Another

Example: 40 is what percentage of 200?

is what % of

3. Percentage Increase or Decrease

Example: Change from 50 to 75 (Percentage Increase).

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How to Calculate Percentage of a Number

Understanding how to calculate percentages is a fundamental mathematical skill used in everyday life, from calculating tax and discounts to analyzing data and financial growth. A percentage represents a part of a whole, expressed as a fraction of 100.

The Basic Percentage Formula

To find the percentage of a specific number, you can use the following formula:

Result = (Percentage / 100) × Number

Step-by-Step Calculation Examples

Example 1: Finding 20% of 150

  1. Divide the percentage by 100: 20 / 100 = 0.2
  2. Multiply the result by the whole number: 0.2 × 150 = 30
  3. Answer: 20% of 150 is 30.

Example 2: Finding what percentage 25 is of 200

If you need to find the percentage proportion between two numbers, use this formula:

Percentage = (Part / Whole) × 100
  1. Divide the part by the whole: 25 / 200 = 0.125
  2. Multiply by 100 to get the percentage: 0.125 × 100 = 12.5%
  3. Answer: 25 is 12.5% of 200.

Calculating Percentage Change (Increase or Decrease)

To find how much a value has changed in terms of percentage:

Percentage Change = ((New Value – Old Value) / Old Value) × 100

If the result is positive, it is a percentage increase. If the result is negative, it represents a percentage decrease.

Common Percentage Use Cases

  • Sales Tax: Calculating the extra cost added to a purchase.
  • Discounts: Determining how much you save during a clearance sale.
  • Interest Rates: Calculating annual returns on savings or costs on loans.
  • Statistics: Expressing demographics or survey results.
  • Grades: Converting raw test scores into a percentage out of 100.
function calculatePercOfVal() { var p = parseFloat(document.getElementById('perc_input_1').value); var n = parseFloat(document.getElementById('perc_input_2').value); var resDiv = document.getElementById('result_1'); if (isNaN(p) || isNaN(n)) { resDiv.innerHTML = "Please enter both values."; resDiv.style.color = "#e74c3c"; return; } var result = (p / 100) * n; resDiv.innerHTML = "Result: " + result.toLocaleString(); resDiv.style.color = "#0073aa"; } function calculateProp() { var part = parseFloat(document.getElementById('prop_input_1').value); var whole = parseFloat(document.getElementById('prop_input_2').value); var resDiv = document.getElementById('result_2'); if (isNaN(part) || isNaN(whole) || whole === 0) { resDiv.innerHTML = "Please enter valid numbers (Whole cannot be 0)."; resDiv.style.color = "#e74c3c"; return; } var result = (part / whole) * 100; resDiv.innerHTML = "Result: " + result.toFixed(2) + "%"; resDiv.style.color = "#0073aa"; } function calculateDiff() { var oldV = parseFloat(document.getElementById('diff_input_1').value); var newV = parseFloat(document.getElementById('diff_input_2').value); var resDiv = document.getElementById('result_3'); if (isNaN(oldV) || isNaN(newV) || oldV === 0) { resDiv.innerHTML = "Please enter valid numbers (Old value cannot be 0)."; resDiv.style.color = "#e74c3c"; return; } var diff = newV – oldV; var percChange = (diff / oldV) * 100; var type = percChange >= 0 ? "Increase" : "Decrease"; resDiv.innerHTML = Math.abs(percChange).toFixed(2) + "% " + type; resDiv.style.color = percChange >= 0 ? "#27ae60" : "#e67e22"; }

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