Use this calculator to determine the weighted average of a set of values, where each value contributes differently to the final average based on its assigned weight.
Result:
.calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
background-color: #f9f9f9;
padding: 25px;
border-radius: 10px;
box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
max-width: 700px;
margin: 30px auto;
border: 1px solid #e0e0e0;
}
.calculator-container h2 {
color: #333;
text-align: center;
margin-bottom: 20px;
font-size: 28px;
}
.calculator-container p {
color: #555;
text-align: center;
margin-bottom: 25px;
line-height: 1.6;
}
.input-group {
display: flex;
flex-wrap: wrap;
align-items: center;
margin-bottom: 15px;
padding: 10px;
background-color: #fff;
border: 1px solid #ddd;
border-radius: 8px;
box-shadow: 0 2px 5px rgba(0,0,0,0.05);
}
.input-group label {
flex: 1 1 120px;
color: #444;
font-weight: bold;
margin-right: 10px;
min-width: 100px;
}
.input-group input[type="number"] {
flex: 2 1 150px;
padding: 10px 12px;
border: 1px solid #ccc;
border-radius: 5px;
margin-right: 15px;
font-size: 16px;
box-sizing: border-box;
}
.input-group button {
flex-shrink: 0;
padding: 8px 15px;
background-color: #dc3545;
color: white;
border: none;
border-radius: 5px;
cursor: pointer;
font-size: 15px;
transition: background-color 0.3s ease;
}
.input-group button:hover {
background-color: #c82333;
}
button[onclick="addRow()"],
button[onclick="calculateWeightedAverage()"] {
display: inline-block;
padding: 12px 25px;
margin: 10px 10px 20px 0;
border: none;
border-radius: 5px;
cursor: pointer;
font-size: 17px;
font-weight: bold;
transition: background-color 0.3s ease, transform 0.2s ease;
}
button[onclick="addRow()"] {
background-color: #007bff;
color: white;
}
button[onclick="addRow()"]:hover {
background-color: #0056b3;
transform: translateY(-2px);
}
button[onclick="calculateWeightedAverage()"] {
background-color: #28a745;
color: white;
}
button[onclick="calculateWeightedAverage()"]:hover {
background-color: #218838;
transform: translateY(-2px);
}
.result-container {
background-color: #e9f7ef;
border: 1px solid #d4edda;
border-radius: 8px;
padding: 20px;
margin-top: 25px;
text-align: center;
}
.result-container h3 {
color: #28a745;
margin-top: 0;
font-size: 22px;
}
.result-output {
color: #000;
font-size: 26px;
font-weight: bold;
margin-top: 10px;
}
@media (max-width: 600px) {
.input-group {
flex-direction: column;
align-items: stretch;
}
.input-group label {
margin-bottom: 5px;
text-align: left;
}
.input-group input[type="number"] {
margin-right: 0;
margin-bottom: 10px;
}
.input-group button {
width: 100%;
margin-top: 5px;
}
button[onclick="addRow()"],
button[onclick="calculateWeightedAverage()"] {
width: 100%;
margin-right: 0;
margin-bottom: 10px;
}
}
var rowCount = 3; // Initial number of rows
function addRow() {
rowCount++;
var inputRowsDiv = document.getElementById('inputRows');
var newRow = document.createElement('div');
newRow.className = 'input-group';
newRow.id = 'row' + rowCount;
newRow.innerHTML = `
`;
inputRowsDiv.appendChild(newRow);
}
function removeRow(id) {
var rowToRemove = document.getElementById('row' + id);
if (rowToRemove) {
rowToRemove.parentNode.removeChild(rowToRemove);
// Re-index remaining rows if needed, or just var the IDs be sparse.
// For simplicity, we'll var IDs be sparse. The calculation loop will iterate through existing IDs.
}
}
function calculateWeightedAverage() {
var sumOfProducts = 0;
var sumOfWeights = 0;
var resultDiv = document.getElementById('weightedAverageResult');
var validInputs = true;
for (var i = 1; i <= rowCount; i++) {
var valueInput = document.getElementById('value' + i);
var weightInput = document.getElementById('weight' + i);
// Check if the row still exists (it might have been removed)
if (valueInput && weightInput) {
var value = parseFloat(valueInput.value);
var weight = parseFloat(weightInput.value);
if (isNaN(value) || isNaN(weight)) {
resultDiv.innerHTML = 'Please enter valid numbers for all values and weights.';
validInputs = false;
break;
}
if (weight < 0) {
resultDiv.innerHTML = 'Weights cannot be negative.';
validInputs = false;
break;
}
sumOfProducts += value * weight;
sumOfWeights += weight;
}
}
if (!validInputs) {
return;
}
if (sumOfWeights === 0) {
resultDiv.innerHTML = 'The sum of weights cannot be zero. Please enter positive weights.';
} else {
var weightedAverage = sumOfProducts / sumOfWeights;
resultDiv.innerHTML = 'The Weighted Average is: ' + weightedAverage.toFixed(4) + '';
}
}
Understanding the Weighted Average
The weighted average is a powerful statistical tool used to calculate the average of a set of numbers, where some numbers contribute more to the final average than others. Unlike a simple average (arithmetic mean), which treats all values equally, a weighted average assigns a 'weight' to each value, reflecting its importance or frequency.
When to Use a Weighted Average?
Weighted averages are commonly used in various fields:
Academics: Calculating a student's final grade where different assignments (e.g., homework, quizzes, exams) have different percentage contributions.
Finance: Determining the average cost of inventory (e.g., Weighted Average Cost method), or calculating portfolio returns where different assets have different allocations.
Statistics: Analyzing survey data where different demographic groups might be weighted to ensure representativeness.
Economics: Calculating inflation rates (Consumer Price Index) where different goods and services have different spending weights.
The Formula for Weighted Average
The formula for calculating a weighted average is:
Weighted Average = (18) + (22.5) + (42.5) / (1.00)
Weighted Average = 83 / 1
Weighted Average = 83
Your weighted average grade would be 83. Notice how the higher weight of the final exam significantly influenced the overall average.
Using the Calculator
Our Weighted Average Calculator simplifies this process. Simply enter each 'Item Value' and its corresponding 'Item Weight'. You can add more items as needed using the "Add Another Item" button. The calculator will instantly provide you with the accurate weighted average, saving you time and reducing calculation errors.