How to Calculate Percentages of a Number

1. Calculate Percentage of a Number

What is X% of Y?

What is % of

2. Calculate Percentage (X is what % of Y?)

Number X is what percentage of number Y?

is what percent of

3. Percentage Increase or Decrease

What is the percentage change from X to Y?

From to

function calcPerc1() { var p = parseFloat(document.getElementById('perc1_p').value); var v = parseFloat(document.getElementById('perc1_v').value); var res = document.getElementById('res1'); if (isNaN(p) || isNaN(v)) { res.innerHTML = "Please enter valid numbers."; return; } var result = (p / 100) * v; res.innerHTML = "Result: " + result.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 4}); } function calcPerc2() { var v1 = parseFloat(document.getElementById('perc2_v1').value); var v2 = parseFloat(document.getElementById('perc2_v2').value); var res = document.getElementById('res2'); if (isNaN(v1) || isNaN(v2) || v2 === 0) { res.innerHTML = "Please enter valid numbers (Value 2 cannot be zero)."; return; } var result = (v1 / v2) * 100; res.innerHTML = "Result: " + result.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 4}) + "%"; } function calcPerc3() { var v1 = parseFloat(document.getElementById('perc3_v1').value); var v2 = parseFloat(document.getElementById('perc3_v2').value); var res = document.getElementById('res3'); if (isNaN(v1) || isNaN(v2) || v1 === 0) { res.innerHTML = "Please enter valid numbers (Old value cannot be zero)."; return; } var result = ((v2 – v1) / Math.abs(v1)) * 100; var direction = (result >= 0) ? "Increase" : "Decrease"; res.innerHTML = "Result: " + Math.abs(result).toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 4}) + "% " + direction; }

How to Calculate Percentages: A Comprehensive Guide

Understanding how to calculate percentages is a fundamental skill used in everything from shopping for sales to analyzing complex business data. At its core, a percentage is a way of expressing a number as a fraction of 100.

Basic Percentage Formula

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

(Percentage / 100) × Total Value = Result

Example: To find 20% of 150, you calculate (20 / 100) × 150. This simplifies to 0.20 × 150 = 30.

Calculating the Percentage Ratio

If you want to find out what percentage one number is of another (e.g., you scored 45 out of 60 on a test), use this formula:

(Part / Whole) × 100 = Percentage

Example: (45 / 60) × 100 = 0.75 × 100 = 75%.

Percentage Increase and Decrease

This is commonly used in finance and statistics to track growth or decline. The formula requires the old value and the new value:

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

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

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
100%	1.0	1/1

Real-World Examples

1. Shopping Discounts: If a jacket costs 80 and is on sale for 25% off, you calculate 0.25 × 80 = 20. The discount is 20, making the final price 60.

2. Salary Raise: If you earn 50,000 per year and receive a 5% raise, your new salary is 50,000 + (50,000 × 0.05) = 52,500.

3. Tip Calculation: To leave a 15% tip on a 40 bill, calculate 40 × 0.15 = 6.

Frequently Asked Questions

What does "percent" mean?
The word "percent" comes from the Latin per centum, which literally means "by the hundred."

Can a percentage be over 100?
Yes. For example, 200% of a number is double that number. If a stock price goes from 10 to 30, it has increased by 200%.

How do I convert a decimal to a percentage?
Simply multiply the decimal by 100 and add the "%" sign. For example, 0.85 becomes 85%.