.irr-calculator-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 0 auto;
padding: 20px;
background-color: #f9f9f9;
border: 1px solid #e0e0e0;
border-radius: 8px;
}
.irr-calc-box {
background: #ffffff;
padding: 25px;
border-radius: 8px;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
margin-bottom: 30px;
}
.irr-input-group {
margin-bottom: 20px;
}
.irr-input-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #333;
}
.irr-input-group input, .irr-input-group textarea {
width: 100%;
padding: 12px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.irr-input-group textarea {
height: 100px;
resize: vertical;
}
.irr-btn {
background-color: #2c3e50;
color: white;
padding: 15px 30px;
border: none;
border-radius: 4px;
cursor: pointer;
font-size: 16px;
font-weight: bold;
width: 100%;
transition: background 0.3s;
}
.irr-btn:hover {
background-color: #34495e;
}
.irr-result-section {
margin-top: 25px;
padding: 20px;
background-color: #f0f7ff;
border-left: 5px solid #2c3e50;
display: none;
}
.irr-result-header {
font-size: 14px;
color: #666;
text-transform: uppercase;
letter-spacing: 1px;
}
.irr-result-value {
font-size: 36px;
font-weight: 700;
color: #2c3e50;
margin: 10px 0;
}
.irr-result-summary {
font-size: 15px;
line-height: 1.5;
color: #444;
}
.irr-error {
color: #d32f2f;
font-weight: bold;
display: none;
margin-top: 10px;
}
.irr-content {
margin-top: 40px;
line-height: 1.6;
color: #333;
}
.irr-content h2 {
color: #2c3e50;
margin-top: 30px;
border-bottom: 2px solid #eee;
padding-bottom: 10px;
}
.irr-content p {
margin-bottom: 15px;
}
.irr-content ul {
margin-bottom: 15px;
padding-left: 20px;
}
.irr-content li {
margin-bottom: 8px;
}
.help-text {
font-size: 12px;
color: #666;
margin-top: 5px;
}
function calculateInternalRateOfReturn() {
var investmentInput = document.getElementById("initialInvestment").value;
var cashFlowsInput = document.getElementById("cashFlows").value;
var resultSection = document.getElementById("resultSection");
var resultValue = document.getElementById("irrResultValue");
var resultSummary = document.getElementById("irrSummary");
var errorDiv = document.getElementById("irrError");
// Reset UI
errorDiv.style.display = "none";
resultSection.style.display = "none";
// Validation
if (!investmentInput || isNaN(parseFloat(investmentInput))) {
errorDiv.innerText = "Please enter a valid Initial Investment amount.";
errorDiv.style.display = "block";
return;
}
if (!cashFlowsInput) {
errorDiv.innerText = "Please enter at least one subsequent cash flow.";
errorDiv.style.display = "block";
return;
}
// Parse Data
// Initial investment is conventionally negative in IRR calculation (outflow)
var initialOutflow = -1 * Math.abs(parseFloat(investmentInput));
// Parse CSV flows
var flowsString = cashFlowsInput.replace(/[^0-9.,-]/g, ","); // Remove non-numeric/separator chars
var flowItems = flowsString.split(/[,\n]+/).filter(function(n) { return n !== "" });
var flows = [];
flows.push(initialOutflow); // Year 0
for (var i = 0; i < flowItems.length; i++) {
var val = parseFloat(flowItems[i]);
if (!isNaN(val)) {
flows.push(val);
}
}
if (flows.length < 2) {
errorDiv.innerText = "Please enter valid numeric cash flows separated by commas.";
errorDiv.style.display = "block";
return;
}
// Algorithm: Newton-Raphson Method
var irr = 0.0;
var guess = 0.1; // Start with 10% guess
var maxIterations = 1000;
var precision = 0.000001;
// Check if sum of flows is positive (required for positive IRR)
var totalFlow = 0;
for(var k=0; k<flows.length; k++) {
totalFlow += flows[k];
}
if (totalFlow <= 0 && initialOutflow < 0) {
// If total cash returned is less than investment, IRR is negative
// Try to estimate negative IRR or just return error
guess = -0.1;
}
var found = false;
for (var iter = 0; iter < maxIterations; iter++) {
var npv = 0;
var derivative = 0;
for (var j = 0; j 0) {
// Derivative of C / (1+r)^j is -j * C / (1+r)^(j+1)
derivative += -j * flows[j] / Math.pow(1 + guess, j + 1);
}
}
var newGuess = guess – (npv / derivative);
// Check convergence
if (Math.abs(newGuess – guess) 0 ? "profit" : "loss";
var totalReturn = totalFlow + Math.abs(initialOutflow); // Gross return
resultSummary.innerHTML = "Based on an initial investment of
.The project breaks even at a discount rate of " + percentage + "%.";
resultSection.style.display = "block";
} else {
errorDiv.innerText = "Could not calculate a valid IRR for these cash flows. The numbers may not converge (e.g., highly irregular alternating positive/negative flows).";
errorDiv.style.display = "block";
}
}
What is Internal Rate of Return (IRR)?
The Internal Rate of Return (IRR) is a financial metric used to estimate the profitability of potential investments. It is the discount rate that makes the Net Present Value (NPV) of all cash flows from a particular project equal to zero.
In simpler terms, it represents the expected compound annual rate of return that will be earned on a project or investment. Generally speaking, the higher a project's IRR, the more desirable it is to undertake.
How to Use This Calculator
This tool calculates the IRR based on an initial cash outflow (investment) and a series of future cash inflows.
- Initial Investment: Enter the amount of money required to start the project. This is treated as a negative cash flow (Year 0) in the calculation.
- Annual Cash Flows: Enter the expected income for each subsequent year. Separate each year's amount with a comma.
Example: If you invest $10,000 today and receive $3,000 next year, $4,000 the year after, and $5,000 in the third year, you would enter "10000" in the first box and "3000, 4000, 5000" in the second box.
The IRR Formula
The calculation tries to find the rate ($r$) that satisfies the following equation:
0 = CF0 + CF1/(1+r)^1 + CF2/(1+r)^2 + … + CFn/(1+r)^n
Where:
- CF0 is the initial investment (negative value).
- CF1, CF2… are the cash flows for each period.
- n is the time period.
- r is the Internal Rate of Return.
Why is IRR Important?
Businesses use IRR for Capital Budgeting to compare the profitability of establishing new operations or expanding existing ones. For example, if a company has a "Hurdle Rate" (Minimum Acceptable Rate of Return) of 10%, any project with an IRR above 10% is typically considered a good investment.
Limitations
While useful, IRR should not be used in isolation. It assumes that future cash flows can be reinvested at the same rate as the IRR, which may not always be realistic. It is often used alongside Net Present Value (NPV) for a comprehensive analysis.