Calculate percentages, markups, discounts, and more with ease.
Increase by Percentage (e.g., Discounted Price)
Decrease by Percentage (e.g., Sale Price)
What is Percentage OF Original Amount (e.g., Tax Amount)
What Percentage is One Amount OF Another
Result: $0.00
Understanding and Calculating Percentages of Money
Percentages are a fundamental concept in finance, business, and everyday life. They represent a part of a whole, expressed as a fraction of 100. Understanding how to calculate percentages is crucial for tasks like determining discounts, calculating taxes, figuring out interest, and analyzing financial growth or decline.
This calculator helps you perform common percentage-related financial calculations quickly and accurately. Let's break down the types of calculations you can perform:
Types of Percentage Calculations
Increase by Percentage: This is used when you want to add a percentage to an original amount. A common example is adding a markup to a cost price to determine a selling price.
New Amount = Original Amount + (Original Amount * (Percentage / 100))
Decrease by Percentage: This is used when you want to subtract a percentage from an original amount. This is most commonly seen with sales discounts.
New Amount = Original Amount – (Original Amount * (Percentage / 100))
What is Percentage OF Original Amount: This calculates the absolute value of the percentage applied to the original amount. This is useful for finding the actual amount of tax, commission, or the amount of a discount itself.
Amount = Original Amount * (Percentage / 100)
What Percentage is One Amount OF Another: This determines what percentage one number is of another. For example, what percentage of your total income is your rent?
Percentage = (Part Amount / Whole Amount) * 100
(Note: For this specific calculation, the "Original Amount" input acts as the "Whole Amount" and a second input would be needed for the "Part Amount." Our calculator simplifies this by having two distinct input fields in this mode.)
How the Calculator Works
The calculator takes your original monetary value and a percentage. Based on your selected calculation type, it applies the relevant formula:
What is Percentage OF Original Amount: Calculates `Original Amount * (Percentage / 100)`.
What Percentage is One Amount OF Another: To accommodate this specific calculation, the calculator dynamically changes its input fields. The first input field becomes the "Part Amount" and the "Original Amount" field becomes the "Whole Amount." The formula used is `(Part Amount / Whole Amount) * 100`.
Real-World Examples
Scenario 1: Sale Discount
An item originally costs $150, and it's on sale for 25% off.
Using "Decrease by Percentage":
Original Amount: $150
Percentage: 25%
Result: $150 * (1 – (25 / 100)) = $150 * 0.75 = $112.50. The sale price is $112.50.
Scenario 2: Sales Tax
You're buying a product for $80, and there's a 7% sales tax.
Using "Increase by Percentage" (to find the final price) or "What is Percentage OF Original Amount" (to find just the tax amount):
Original Amount: $80
Percentage: 7%
Tax Amount: $80 * (7 / 100) = $5.60
Final Price: $80 + $5.60 = $85.60 (or $80 * (1 + (7/100)) = $85.60)
Scenario 3: Investment Growth
You invested $2,000, and it grew by 10% in one year.
Using "Increase by Percentage":
Original Amount: $2,000
Percentage: 10%
Result: $2,000 * (1 + (10 / 100)) = $2,000 * 1.10 = $2,200. Your investment is now worth $2,200.
Scenario 4: Performance Comparison
Team A scored 50 goals, and Team B scored 40 goals. What percentage of Team A's goals did Team B score?
Using "What Percentage is One Amount OF Another":
Original Amount (Whole): 50
Input 2 (Part): 40
Result: (40 / 50) * 100 = 0.8 * 100 = 80%. Team B scored 80% of Team A's goals.
function calculatePercentage() {
var originalAmountInput = document.getElementById("originalAmount");
var percentageInput = document.getElementById("percentage");
var calculationTypeSelect = document.getElementById("calculationType");
var resultDiv = document.getElementById("result");
var originalAmount = parseFloat(originalAmountInput.value);
var percentage = parseFloat(percentageInput.value);
var calculationType = calculationTypeSelect.value;
var result = 0;
var formattedResult = "";
if (isNaN(originalAmount) || isNaN(percentage)) {
resultDiv.innerHTML = 'Please enter valid numbers for all fields.';
return;
}
if (calculationType === "increase") {
result = originalAmount * (1 + (percentage / 100));
formattedResult = result.toFixed(2);
resultDiv.innerHTML = 'Final Amount: $' + formattedResult + ";
} else if (calculationType === "decrease") {
result = originalAmount * (1 – (percentage / 100));
formattedResult = result.toFixed(2);
resultDiv.innerHTML = 'Final Amount: $' + formattedResult + ";
} else if (calculationType === "of") {
result = originalAmount * (percentage / 100);
formattedResult = result.toFixed(2);
resultDiv.innerHTML = 'Amount: $' + formattedResult + ";
} else if (calculationType === "percentOf") {
// For "percentOf", originalAmount is the whole, percentage input is the part.
// We need to swap the roles conceptually for this calculation.
var partAmount = parseFloat(percentageInput.value); // Use percentage input as the part
var wholeAmount = parseFloat(originalAmountInput.value); // Use original amount as the whole
if (isNaN(partAmount) || isNaN(wholeAmount) || wholeAmount === 0) {
resultDiv.innerHTML = 'Please enter valid numbers. For "What Percentage is One Amount OF Another", ensure the original amount (whole) is not zero.';
return;
}
result = (partAmount / wholeAmount) * 100;
formattedResult = result.toFixed(2);
resultDiv.innerHTML = 'Percentage: ' + formattedResult + '%';
}
}
// Initial setup for "What Percentage is One Amount OF Another" to guide user
var calculationTypeSelect = document.getElementById("calculationType");
var originalAmountLabel = document.querySelector('label[for="originalAmount"]');
var percentageLabel = document.querySelector('label[for="percentage"]');
function updateLabelsForPercentOf() {
if (calculationTypeSelect.value === "percentOf") {
originalAmountLabel.textContent = "Whole Amount ($)";
percentageLabel.textContent = "Part Amount ($)";
document.getElementById("originalAmount").placeholder = "e.g., 200 (the whole)";
document.getElementById("percentage").placeholder = "e.g., 50 (the part)";
} else {
originalAmountLabel.textContent = "Original Amount ($)";
percentageLabel.textContent = "Percentage (%)";
document.getElementById("originalAmount").placeholder = "e.g., 100";
document.getElementById("percentage").placeholder = "e.g., 15";
}
}
calculationTypeSelect.addEventListener("change", updateLabelsForPercentOf);
updateLabelsForPercentOf(); // Set initial labels