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.calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
background-color: #f9f9f9;
border: 1px solid #ddd;
border-radius: 8px;
padding: 25px;
max-width: 500px;
margin: 30px auto;
box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}
.calculator-container h2 {
text-align: center;
color: #2c3e50;
margin-bottom: 25px;
font-size: 1.8em;
}
.calculator-content {
display: flex;
flex-direction: column;
}
.input-group {
margin-bottom: 15px;
display: flex;
flex-direction: column;
}
.input-group label {
margin-bottom: 7px;
color: #34495e;
font-size: 0.95em;
font-weight: 600;
}
.input-group input[type="number"],
.input-group select {
padding: 10px 12px;
border: 1px solid #ccc;
border-radius: 5px;
font-size: 1em;
width: 100%;
box-sizing: border-box;
transition: border-color 0.3s ease;
}
.input-group input[type="number"]:focus,
.input-group select:focus {
border-color: #007bff;
outline: none;
box-shadow: 0 0 0 2px rgba(0, 123, 255, 0.25);
}
.calculate-button {
background-color: #28a745;
color: white;
padding: 12px 20px;
border: none;
border-radius: 5px;
font-size: 1.1em;
cursor: pointer;
margin-top: 20px;
transition: background-color 0.3s ease, transform 0.2s ease;
width: 100%;
box-sizing: border-box;
}
.calculate-button:hover {
background-color: #218838;
transform: translateY(-2px);
}
.calculate-button:active {
transform: translateY(0);
}
.result-container {
background-color: #e9f7ef;
border: 1px solid #d4edda;
border-radius: 8px;
padding: 20px;
margin-top: 25px;
font-size: 1.1em;
color: #155724;
line-height: 1.6;
}
.result-container p {
margin: 0 0 8px 0;
}
.result-container p:last-child {
margin-bottom: 0;
}
.result-container strong {
color: #0f3d1a;
}
function calculateBondValue() {
var bondSeries = document.getElementById("bondSeries").value;
var originalPurchaseAmount = parseFloat(document.getElementById("originalPurchaseAmount").value);
var purchaseMonth = parseInt(document.getElementById("purchaseMonth").value);
var purchaseYear = parseInt(document.getElementById("purchaseYear").value);
var currentMonth = parseInt(document.getElementById("currentMonth").value);
var currentYear = parseInt(document.getElementById("currentYear").value);
var assumedAnnualRate = parseFloat(document.getElementById("assumedAnnualRate").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
// Input validation
if (isNaN(originalPurchaseAmount) || originalPurchaseAmount <= 0) {
resultDiv.innerHTML = "Please enter a valid Original Purchase Amount.";
return;
}
if (isNaN(purchaseMonth) || isNaN(purchaseYear) || isNaN(currentMonth) || isNaN(currentYear)) {
resultDiv.innerHTML = "Please select valid purchase and current dates.";
return;
}
if (isNaN(assumedAnnualRate) || assumedAnnualRate currentDate) {
resultDiv.innerHTML = "Purchase Date cannot be in the future relative to the Current Date.";
return;
}
// Calculate duration in years
var yearsDiff = currentDate.getFullYear() – purchaseDate.getFullYear();
var monthsDiff = currentDate.getMonth() – purchaseDate.getMonth();
var totalYearsHeld = yearsDiff + (monthsDiff / 12);
// Convert annual rate to decimal
var rateDecimal = assumedAnnualRate / 100;
// Compound interest formula: FV = P * (1 + r)^t
var estimatedCurrentValue = originalPurchaseAmount * Math.pow((1 + rateDecimal), totalYearsHeld);
var estimatedTotalInterest = estimatedCurrentValue – originalPurchaseAmount;
resultDiv.innerHTML =
"Bond Series: " + bondSeries + "" +
"Original Purchase Amount: $" + originalPurchaseAmount.toFixed(2) + "" +
"Years Held (approx): " + totalYearsHeld.toFixed(2) + " years" +
"Estimated Current Value:$" + estimatedCurrentValue.toFixed(2) + "" +
"Estimated Total Interest Earned:$" + estimatedTotalInterest.toFixed(2) + "" +
"Note: This is an estimation based on a constant assumed annual rate and does not account for actual historical bond rates, which vary.";
}
// Set current month and year as defaults
window.onload = function() {
var today = new Date();
document.getElementById("currentMonth").value = today.getMonth() + 1;
document.getElementById("currentYear").value = today.getFullYear();
};
Understanding TreasuryDirect Savings Bonds and This Estimator
TreasuryDirect Savings Bonds are a popular, low-risk investment option offered by the U.S. Department of the Treasury. They are backed by the full faith and credit of the U.S. government, making them one of the safest investments available. There are two main types of savings bonds: EE bonds and I bonds.
EE Bonds
Fixed Rate: EE bonds earn a fixed rate of interest for 20 years. If held for 20 years, their value is guaranteed to at least double.
Maturity: They continue to earn interest for a total of 30 years.
Purchase: Can be purchased electronically through TreasuryDirect.
I Bonds
Variable Rate: I bonds earn a composite interest rate that combines a fixed rate (which can be zero) and a variable inflation rate. The inflation rate is adjusted every six months (May and November).
Inflation Protection: Designed to protect your investment from inflation, as their interest rate adjusts with the Consumer Price Index (CPI).
Maturity: They earn interest for 30 years.
Purchase: Also purchased electronically through TreasuryDirect.
How Savings Bonds Work
Both EE and I bonds accrue interest monthly, and this interest is compounded semiannually. This means that the interest you earn starts earning interest itself, leading to growth over time. You don't receive interest payments directly; instead, the value of your bond increases. You can redeem bonds after 12 months, but if you redeem them before 5 years, you forfeit the last three months of interest.
About This Savings Bond Estimator
The official TreasuryDirect website provides a precise tool to track the exact value of your savings bonds based on their specific issue date and historical interest rates. However, this calculator offers a simplified estimation of your bond's potential value.
Important Note: This calculator uses a standard compound interest formula based on an assumed annual interest rate that you provide. It does not account for the complex, varying interest rate structures of actual EE or I bonds, especially the semi-annual adjustments for I bonds or the guaranteed doubling feature of EE bonds. Therefore, the results should be used as a general guide or for projecting growth under a consistent rate, not as an exact valuation.
How to Use the Calculator:
Bond Series: Select whether your bond is an EE or I bond. While this calculator uses a simplified interest model, selecting the series provides context.
Original Purchase Amount ($): Enter the initial amount you paid for the bond.
Purchase Month/Year: Input the month and year your bond was issued.
Current Month/Year: Input the current month and year up to which you want to estimate the value.
Assumed Annual Interest Rate (%): This is the crucial input for this estimator. Enter an average annual interest rate you wish to use for the calculation. For a rough estimate, you might use a historical average for the bond type, or a rate you expect.
Click "Calculate Estimated Value" to see the projected current value and the total estimated interest earned.
Example Calculation:
Let's say you purchased an EE Bond for $500 in January 2015, and you want to estimate its value up to January 2025, assuming an average annual interest rate of 2.5%.
Bond Series: EE Bond
Original Purchase Amount: $500
Purchase Month: January
Purchase Year: 2015
Current Month: January
Current Year: 2025
Assumed Annual Interest Rate: 2.5%
The calculator would determine that the bond has been held for 10 years. Using the compound interest formula (FV = P * (1 + r)^t):
FV = $500 * (1 + 0.025)^10
FV = $500 * (1.025)^10
FV ≈ $500 * 1.28008
Estimated Current Value: ~$640.04
Estimated Total Interest Earned: ~$140.04
This example demonstrates how the calculator provides a quick projection based on your chosen average rate and holding period.