Optimal Portfolio Weight Calculator

Determine Your Ideal Asset Allocation

Your Optimal Portfolio Weights

The optimal weights are calculated to achieve the target portfolio volatility based on Modern Portfolio Theory (MPT), minimizing risk for a given return or maximizing return for a given risk. The specific formula involves solving for weights (w1, w2) in the portfolio volatility equation: σp² = w1²σ1² + w2²σ2² + 2w1w2ρσ1σ2, given w1 + w2 = 1 and the target σp.

What is Optimal Portfolio Weight?

The concept of optimal portfolio weight refers to the specific proportion or percentage of your total investment capital that should be allocated to each individual asset within your investment portfolio. The goal is to achieve a balance between risk and return that aligns with your financial objectives and risk tolerance. Determining these weights is a cornerstone of modern portfolio theory (MPT), pioneered by Harry Markowitz. It's not just about picking good assets; it's about combining them in a way that maximizes diversification benefits and minimizes overall portfolio risk for a given level of expected return.

Optimal portfolio weight calculations are crucial for investors who aim to construct a robust and efficient portfolio. This includes individual retail investors, financial advisors managing client assets, and institutional investors. It's particularly useful when adding new assets to an existing portfolio or when rebalancing your holdings to maintain your desired risk-return profile.

A common misconception about optimal portfolio weight is that it involves complex, inaccessible mathematics reserved only for Wall Street quants. While the underlying theory can be intricate, practical calculators like this one simplify the process significantly. Another misconception is that "optimal" means a single, fixed allocation for everyone; in reality, optimal weights are highly personalized, depending on individual risk tolerance, return expectations, and market conditions. The idea isn't to eliminate risk, but to manage it efficiently.

Who Should Use an Optimal Portfolio Weight Calculator?

• Long-Term Investors: Those building wealth over years or decades benefit from disciplined asset allocation.
• Risk-Conscious Investors: Individuals who want to understand and control their portfolio's volatility.
• Diversification Seekers: Investors looking to maximize the benefits of combining different asset classes.
• Financial Advisors: Professionals using data-driven methods to construct client portfolios.
• Rebalancing Efforts: Anyone needing to adjust their portfolio back to its target allocation.

Common Misconceptions

• "Optimal" is Static: Optimal weights change based on market conditions and personal goals.
• Eliminates All Risk: It aims to *manage* risk, not eliminate it.
• Only for Experts: Calculators make it accessible to all investors.
• Guarantees High Returns: It optimizes the risk-return trade-off, not guarantees specific outcomes.

Optimal Portfolio Weight Formula and Mathematical Explanation

The foundation for calculating optimal portfolio weight lies in Modern Portfolio Theory (MPT). MPT seeks to create a portfolio that offers the highest expected return for a defined level of risk or the lowest risk for a given level of expected return. For a two-asset portfolio, the core principle involves balancing the weights (w1 and w2) of the two assets to achieve a specific target portfolio volatility (σp).

The formula for the variance (σp²) of a two-asset portfolio is:

σp² = w₁²σ₁² + w₂²σ₂² + 2w₁w₂ρσ₁σ₂

Where:

• σp² is the portfolio variance (the square of portfolio volatility).
• w₁ is the weight (proportion) of Asset 1 in the portfolio.
• w₂ is the weight (proportion) of Asset 2 in the portfolio.
• σ₁ is the volatility (standard deviation) of Asset 1.
• σ₂ is the volatility (standard deviation) of Asset 2.
• ρ (rho) is the correlation coefficient between Asset 1 and Asset 2.

We also know that the weights must sum to 1:

w₁ + w₂ = 1

This means w₂ = 1 – w₁. Substituting this into the portfolio variance formula allows us to express the portfolio volatility solely as a function of w₁:

σp² = w₁²σ₁² + (1-w₁)²σ₂² + 2w₁(1-w₁)ρσ₁σ₂

The calculator solves this equation for w₁ (and subsequently w₂ = 1 – w₁) such that the resulting σp matches the user's Target Portfolio Volatility. This often involves numerical methods or solving a quadratic equation derived from setting the derivative of the variance equation with respect to w₁ to zero, depending on the exact optimization goal (e.g., minimum variance portfolio vs. target volatility portfolio). Our calculator uses an iterative approach to find the weights that satisfy the target volatility.

Variables Table

Key variables used in determining optimal portfolio weight.

Variable	Meaning	Unit	Typical Range
Expected Return (Asset 1/2)	The anticipated annualized gain from an asset.	%	-10% to 30%+ (highly variable)
Volatility (Asset 1/2)	A measure of an asset's price fluctuation; indicates risk.	% (Standard Deviation)	1% to 50%+ (highly variable)
Correlation Coefficient (ρ)	Statistical measure of how two assets' prices move in relation to each other.	Decimal / Ratio	-1 (perfectly inverse) to +1 (perfectly correlated)
Target Portfolio Volatility (σp)	The desired level of risk for the overall portfolio.	% (Standard Deviation)	5% to 25% (common range)
Optimal Weight (w1/w2)	The calculated proportion of each asset in the portfolio for the target risk.	%	0% to 100%

Practical Examples (Real-World Use Cases)

Example 1: Balanced Growth Portfolio

An investor seeks a balanced portfolio with moderate growth and risk. They identify two primary asset classes:

• Asset 1 (Growth Stocks): Expected Return = 12%, Volatility = 18%
• Asset 2 (Core Bonds): Expected Return = 5%, Volatility = 6%
• Correlation: 0.25 (Stocks and bonds tend to move somewhat independently)
• Target Portfolio Volatility: 10%

Using the calculator:

Inputting these values yields:

• Optimal Weight Asset 1: 45.0%
• Optimal Weight Asset 2: 55.0%
• Portfolio Expected Return: 8.10%

Interpretation: To achieve a target volatility of 10%, this investor should allocate 45% to growth stocks and 55% to core bonds. This combination offers a blend of growth potential from stocks while the significant bond allocation (and their low correlation) helps manage the overall portfolio risk.

Example 2: Conservative Income Portfolio

A retiree prioritizes capital preservation and stable income, willing to accept lower growth.

• Asset 1 (Dividend Stocks): Expected Return = 8%, Volatility = 14%
• Asset 2 (High-Quality Bonds): Expected Return = 4%, Volatility = 4%
• Correlation: 0.10 (Low correlation, bonds acting as a buffer)
• Target Portfolio Volatility: 7%

Using the calculator:

Inputting these values results in:

• Optimal Weight Asset 1: 25.0%
• Optimal Weight Asset 2: 75.0%
• Portfolio Expected Return: 5.20%

Interpretation: For a retiree needing stability (target 7% volatility), a heavy allocation to bonds (75%) is optimal. The smaller 25% allocation to dividend stocks provides some potential for growth and income while keeping overall risk low. The portfolio's expected return is modest but aligns with the conservative risk profile. This demonstrates how optimal portfolio weight serves different investor profiles.

How to Use This Optimal Portfolio Weight Calculator

This optimal portfolio weight calculator is designed for ease of use. Follow these simple steps to determine your ideal asset allocation:

1. Input Asset Details: For each of the two assets you are considering (e.g., stocks and bonds, or two different stock ETFs), enter their estimated Expected Return (annualized percentage) and Volatility (annualized standard deviation, a measure of risk) in percentages.
2. Enter Correlation: Provide the Correlation Coefficient between the two assets. This value ranges from -1 (they move in opposite directions) to +1 (they move in the same direction). A value closer to 0 indicates low correlation, which is ideal for diversification.
3. Define Target Risk: Specify your desired overall Target Portfolio Volatility (in percentage). This is the maximum level of risk you are comfortable taking with your combined investments.
4. Calculate: Click the "Calculate Weights" button.

Reading the Results:

• Main Result (Primary Highlighted): This shows the calculated Optimal Weight for Asset 1. The weight for Asset 2 is implicitly 100% minus this value.
• Intermediate Values: These display the calculated Optimal Weight for Asset 2, and the Portfolio Expected Return you can anticipate with this allocation.
• Formula Explanation: Provides a brief overview of the MPT principles used.

Decision-Making Guidance:

• Compare the calculated weights to your current portfolio. If they differ significantly, consider rebalancing.
• Use the results as a guide. Adjust your target volatility based on your life stage and risk tolerance. A lower target volatility will result in a more conservative allocation (higher weight to lower-risk assets).
• Remember that expected returns and volatilities are estimates. Market conditions change, so periodic review and recalculation are essential for maintaining an optimal portfolio weight strategy.

Reset and Copy: Use the "Reset Defaults" button to clear your inputs and start over. The "Copy Results" button allows you to easily save the calculated weights and key figures.

Key Factors That Affect Optimal Portfolio Weight Results

Several critical factors influence the calculation and appropriateness of optimal portfolio weight:

1. Risk Tolerance: This is perhaps the most personal factor. An aggressive investor might tolerate higher volatility for potentially higher returns, leading to higher weights in riskier assets. A conservative investor will aim for lower target volatility, shifting weights towards safer assets like bonds.
2. Time Horizon: Investors with longer time horizons (e.g., young people saving for retirement) can generally afford to take on more risk, as they have more time to recover from market downturns. This allows for higher weights in growth-oriented assets like equities. Short time horizons necessitate lower risk and thus different optimal weights.
3. Market Conditions & Economic Outlook: Expected returns, volatilities, and correlations are not static. During periods of economic uncertainty, correlations might increase, reducing diversification benefits. Conversely, stable growth periods might see different asset class performances. Adjusting expectations based on the current environment is key.
4. Correlation Between Assets: Low or negative correlation is the bedrock of diversification. If assets move in sync (high positive correlation), combining them offers little risk reduction. Assets with low correlation allow for a more efficient frontier, potentially achieving the target volatility with higher expected returns or lower risk for a given return. Understanding and estimating this accurately is vital for determining optimal portfolio weight.
5. Inflation Rates: High inflation erodes the purchasing power of returns. Investors need to consider whether their expected returns outpace inflation. Assets like inflation-protected securities (TIPS) or certain commodities might be considered, influencing the optimal weights within the broader portfolio.
6. Fees and Taxes: Investment management fees, trading costs, and taxes on capital gains or income can significantly reduce net returns. High-fee investments might require higher gross returns to be considered "optimal." Tax implications (e.g., capital gains vs. ordinary income) can also influence asset location and weighting decisions.
7. Specific Investment Goals: Beyond general risk/return, goals like generating retirement income, saving for a down payment, or preserving capital dictate the required portfolio characteristics, thereby influencing the optimal portfolio weight for each asset class.

Frequently Asked Questions (FAQ)

What is the difference between optimal portfolio weight and diversification?

Diversification is the strategy of spreading investments across various asset classes to reduce risk. Optimal portfolio weight is the specific mathematical calculation of *how much* to allocate to each diversified asset to achieve a desired risk-return profile, often based on diversification principles.

Can I use this calculator for more than two assets?

This specific calculator is designed for a two-asset portfolio for simplicity. Calculating optimal weights for portfolios with many assets requires more complex optimization techniques (e.g., quadratic programming) often found in specialized financial software. However, the principles remain the same.

Are the inputs (Expected Return, Volatility) estimates or guarantees?

They are historical estimates and future projections, not guarantees. Past performance is not indicative of future results. Market conditions change, and actual returns and volatilities can differ significantly from estimates.

What does a correlation coefficient of 0 mean for optimal portfolio weight?

A correlation of 0 means the assets' movements are statistically independent. This provides excellent diversification benefits. When calculating optimal portfolio weight with zero correlation, the portfolio volatility is primarily driven by the weighted average of individual asset volatilities, often allowing for higher returns at a given risk level compared to highly correlated assets.

How often should I re-evaluate my optimal portfolio weights?

It's generally recommended to review your portfolio and re-evaluate your optimal portfolio weight at least annually, or whenever significant life events occur (e.g., change in income, retirement, major purchase) or market conditions drastically change.

What if my target portfolio volatility is very high or very low?

If your target volatility is extremely high, the calculator might suggest very aggressive weights (potentially over 100% in a risky asset if leverage were considered, though this calculator assumes weights between 0-100%). If it's extremely low, it might suggest a very high allocation to the lower-risk asset, potentially resulting in a low expected return. Ensure your target aligns realistically with your goals and risk capacity.

Does the calculator account for different asset types like real estate or commodities?

This calculator is simplified for two generic asset classes. Real estate, commodities, and alternatives have different risk/return profiles and correlation behaviors. Incorporating them requires more sophisticated multi-asset optimization models.

What happens if the correlation is negative?

A negative correlation (e.g., -0.5) means the assets tend to move in opposite directions. This is highly beneficial for diversification. When calculating optimal portfolio weight, negative correlation can significantly reduce overall portfolio volatility, potentially allowing for higher expected returns at your target risk level compared to assets with positive correlation.

// Chart Drawing Function function drawChart(weight1, volatility1, volatility2, correlation, targetRisk) { var ctx = document.getElementById('portfolioChart').getContext('2d'); if (window.myPortfolioChart) { window.myPortfolioChart.destroy(); } // Calculate a range of weights for the chart var weights = []; var portfolioVolatilities = []; var portfolioReturns = []; for (var w1 = 0; w1 Math.abs(w – optimalW1Percent) < 0.01); window.myPortfolioChart = new Chart(ctx, { type: 'line', data: { labels: weights, // Weight of Asset 1 (%) datasets: [{ label: 'Portfolio Volatility (%)', data: portfolioVolatilities, borderColor: '#004a99', backgroundColor: 'rgba(0, 74, 153, 0.1)', fill: false, tension: 0.1, pointRadius: 0 // Hide individual points on the line }, { label: 'Portfolio Expected Return (%)', data: portfolioReturns, borderColor: '#28a745', backgroundColor: 'rgba(40, 167, 69, 0.1)', fill: false, tension: 0.1, borderDash: [5, 5], // Dashed line for returns pointRadius: 0 }] }, options: { responsive: true, maintainAspectRatio: false, scales: { x: { title: { display: true, text: 'Weight of Asset 1 (%)' } }, y: { title: { display: true, text: 'Percentage (%)' } } }, plugins: { tooltip: { callbacks: { label: function(context) { var label = context.dataset.label || ''; if (label) { label += ': '; } if (context.parsed.y !== null) { label += context.parsed.y.toFixed(2) + '%'; } return label; } } }, legend: { display: true, position: 'top', } }, hover: { mode: 'index', intersect: false }, // Highlight the optimal point annotation: closestIndex !== -1 ? { annotations: [{ type: 'point', xValue: weights[closestIndex], yValue: portfolioVolatilities[closestIndex], backgroundColor: 'rgba(255, 0, 0, 0.5)', borderColor: 'red', borderWidth: 2, radius: 6, label: { content: `Optimal (${weight1.toFixed(1)}% A1)`, enabled: true, position: 'top', font: { size: 10 } } }] } : {} } }); } // Simplified Chart.js instance (assuming it's loaded elsewhere or embedded) // In a real-world scenario, you'd include Chart.js library. // For this example, we'll mock it. If running this standalone, you'd need: // // // For this exercise, we'll define a dummy Chart object if not present. if (typeof Chart === 'undefined') { console.warn("Chart.js not loaded. Mocking Chart object for demonstration."); window.Chart = function(ctx, config) { this.ctx = ctx; this.config = config; this.destroy = function() { console.log("Mock destroy called"); }; console.log("Mock Chart created with config:", config); return this; }; window.Chart.defaults = { controllers: {} }; // Basic mock // Mock plugin if annotation plugin is used if (typeof Chart.register === 'function') { Chart.register({ id: 'annotation', afterDraw: function() {} }); } else { window.Chart.pluginService = { register: function(plugin) { console.log("Mock plugin registered:", plugin.id); }}; } } // Placeholder for annotation plugin if not loaded if (typeof Chart.register !== 'function' && typeof Chart.pluginService === 'undefined') { console.warn("Chart.js annotation plugin not detected. Annotations might not render."); window.Chart.pluginService = { register: function() {} }; // Mock registration } else if (typeof Chart.register === 'function' && typeof Chart.defaults.plugins.annotation === 'undefined') { // Register mock annotation plugin if Chart.js is modern but plugin isn't registered Chart.register({ id: 'annotation', afterDraw: function(chart, args, options) { if (options.annotations && options.annotations.length > 0) { console.log("Mock annotation drawing:", options.annotations); // In a real scenario, this would draw the annotation } } }); } function validateInput(id, min, max, allowEmpty = false) { var input = document.getElementById(id); var errorElement = document.getElementById('error-' + id); var value = input.value.trim(); var numValue = parseFloat(value); errorElement.innerText = "; errorElement.classList.remove('visible'); input.style.borderColor = '#ccc'; // Reset border color if (!allowEmpty && value === ") { errorElement.innerText = 'This field cannot be empty.'; errorElement.classList.add('visible'); input.style.borderColor = '#dc3545'; return false; } if (value !== " && isNaN(numValue)) { errorElement.innerText = 'Please enter a valid number.'; errorElement.classList.add('visible'); input.style.borderColor = '#dc3545'; return false; } if (value !== ") { if (min !== null && numValue max) { errorElement.innerText = `Value cannot exceed ${max}.`; errorElement.classList.add('visible'); input.style.borderColor = '#dc3545'; return false; } } return true; } function calculatePortfolioWeights() { var isValid = true; // Validate inputs if (!validateInput('expectedReturnAsset1', -100, 100) || !validateInput('volatilityAsset1', 0, 100) || !validateInput('expectedReturnAsset2', -100, 100) || !validateInput('volatilityAsset2', 0, 100) || !validateInput('correlation', -1, 1) || !validateInput('targetRisk', 0, 100)) { isValid = false; } if (!isValid) { document.getElementById('main-result-weight').innerText = 'Invalid Input'; document.getElementById('optimalWeightAsset1').innerText = '–'; document.getElementById('optimalWeightAsset2').innerText = '–'; document.getElementById('portfolioExpectedReturn').innerText = '–'; return; } var expReturn1 = parseFloat(document.getElementById('expectedReturnAsset1').value); var vol1 = parseFloat(document.getElementById('volatilityAsset1').value) / 100; // Standard deviation var expReturn2 = parseFloat(document.getElementById('expectedReturnAsset2').value); var vol2 = parseFloat(document.getElementById('volatilityAsset2').value) / 100; // Standard deviation var corr = parseFloat(document.getElementById('correlation').value); var targetRisk = parseFloat(document.getElementById('targetRisk').value) / 100; // Target standard deviation var optimalW1 = 0; var optimalW2 = 0; var portfolioExpReturn = 0; // Calculation logic: Find w1 such that portfolio volatility matches targetRisk // We use an iterative approach to solve for w1 in the equation: // targetRisk^2 = w1^2*vol1^2 + (1-w1)^2*vol2^2 + 2*w1*(1-w1)*corr*vol1*vol2 var targetRiskSq = targetRisk * targetRisk; var bestW1 = -1; var minDiff = Infinity; // Iterate through possible weights for Asset 1 (0% to 100%) for (var w1_iter = 0; w1_iter <= 1; w1_iter += 0.001) { var w2_iter = 1 – w1_iter; var portfolioVar = Math.pow(w1_iter, 2) * Math.pow(vol1, 2) + Math.pow(w2_iter, 2) * Math.pow(vol2, 2) + 2 * w1_iter * w2_iter * corr * vol1 * vol2; var portfolioStdDev = Math.sqrt(portfolioVar); var diff = Math.abs(portfolioStdDev – targetRisk); if (diff < minDiff) { minDiff = diff; bestW1 = w1_iter; } } optimalW1 = bestW1; optimalW2 = 1 – optimalW1; // Ensure weights are within bounds [0, 1] due to potential floating point inaccuracies optimalW1 = Math.max(0, Math.min(1, optimalW1)); optimalW2 = Math.max(0, Math.min(1, optimalW2)); // Recalculate final portfolio return with the determined weights portfolioExpReturn = optimalW1 * expReturn1 + optimalW2 * expReturn2; // Display results document.getElementById('main-result-weight').innerText = (optimalW1 * 100).toFixed(1) + '%'; document.getElementById('optimalWeightAsset1').innerText = (optimalW1 * 100).toFixed(1) + '%'; document.getElementById('optimalWeightAsset2').innerText = (optimalW2 * 100).toFixed(1) + '%'; document.getElementById('portfolioExpectedReturn').innerText = portfolioExpReturn.toFixed(2) + '%'; // Draw the chart drawChart(optimalW1 * 100, vol1 * 100, vol2 * 100, corr, targetRisk * 100); } function resetCalculator() { document.getElementById('expectedReturnAsset1').value = '10'; document.getElementById('volatilityAsset1').value = '15'; document.getElementById('expectedReturnAsset2').value = '5'; document.getElementById('volatilityAsset2').value = '7'; document.getElementById('correlation').value = '0.3'; document.getElementById('targetRisk').value = '10'; document.getElementById('main-result-weight').innerText = '–'; document.getElementById('optimalWeightAsset1').innerText = '–'; document.getElementById('optimalWeightAsset2').innerText = '–'; document.getElementById('portfolioExpectedReturn').innerText = '–'; // Clear chart if it exists if (window.myPortfolioChart) { window.myPortfolioChart.destroy(); window.myPortfolioChart = null; var canvas = document.getElementById('portfolioChart'); var context = canvas.getContext('2d'); context.clearRect(0, 0, canvas.width, canvas.height); } // Clear error messages var errorElements = document.querySelectorAll('.error-message'); for (var i = 0; i < errorElements.length; i++) { errorElements[i].innerText = ''; errorElements[i].classList.remove('visible'); } var inputs = document.querySelectorAll('.input-group input'); for (var i = 0; i < inputs.length; i++) { inputs[i].style.borderColor = '#ccc'; } } function copyResults() { var mainResult = document.getElementById('main-result-weight').innerText; var optW1 = document.getElementById('optimalWeightAsset1').innerText; var optW2 = document.getElementById('optimalWeightAsset2').innerText; var portReturn = document.getElementById('portfolioExpectedReturn').innerText; var expR1 = document.getElementById('expectedReturnAsset1').value; var vol1 = document.getElementById('volatilityAsset1').value; var expR2 = document.getElementById('expectedReturnAsset2').value; var vol2 = document.getElementById('volatilityAsset2').value; var corr = document.getElementById('correlation').value; var targetR = document.getElementById('targetRisk').value; var resultsText = "— Optimal Portfolio Weights Results —\n\n"; resultsText += "Optimal Weight Asset 1: " + mainResult + "\n"; resultsText += "Optimal Weight Asset 2: " + optW2 + "\n"; resultsText += "Portfolio Expected Return: " + portReturn + "\n\n"; resultsText += "— Key Assumptions —\n"; resultsText += "Asset 1 Expected Return: " + expR1 + "%\n"; resultsText += "Asset 1 Volatility: " + vol1 + "%\n"; resultsText += "Asset 2 Expected Return: " + expR2 + "%\n"; resultsText += "Asset 2 Volatility: " + vol2 + "%\n"; resultsText += "Correlation Coefficient: " + corr + "\n"; resultsText += "Target Portfolio Volatility: " + targetR + "%\n"; try { navigator.clipboard.writeText(resultsText).then(function() { // Optionally provide feedback to the user var btn = document.querySelector('.btn-copy'); var originalText = btn.innerText; btn.innerText = 'Copied!'; setTimeout(function() { btn.innerText = originalText; }, 1500); }).catch(function(err) { console.error('Failed to copy text: ', err); alert('Failed to copy results. Please copy manually.'); }); } catch (err) { console.error('Clipboard API not available or failed: ', err); // Fallback for older browsers or environments without clipboard access var textArea = document.createElement("textarea"); textArea.value = resultsText; textArea.style.position = "fixed"; // Avoid scrolling to bottom textArea.style.left = "-9999px"; document.body.appendChild(textArea); textArea.focus(); textArea.select(); try { var successful = document.execCommand('copy'); var msg = successful ? 'successful' : 'unsuccessful'; console.log('Fallback: Copying text command was ' + msg); var btn = document.querySelector('.btn-copy'); var originalText = btn.innerText; btn.innerText = 'Copied!'; setTimeout(function() { btn.innerText = originalText; }, 1500); } catch (err) { console.error('Fallback: Oops, unable to copy', err); alert('Failed to copy results. Please copy manually.'); } document.body.removeChild(textArea); } } function toggleFaq(element) { var faqItem = element.closest('.faq-item'); faqItem.classList.toggle('open'); } // Initial calculation on page load if defaults are set document.addEventListener('DOMContentLoaded', function() { // Check if default values are present before calculating if (document.getElementById('expectedReturnAsset1').value && document.getElementById('volatilityAsset1').value && document.getElementById('expectedReturnAsset2').value && document.getElementById('volatilityAsset2').value && document.getElementById('correlation').value && document.getElementById('targetRisk').value) { calculatePortfolioWeights(); } // Add event listeners to inputs for real-time updates var inputs = document.querySelectorAll('#calculator-form input[type="number"]'); for (var i = 0; i < inputs.length; i++) { inputs[i].addEventListener('input', function() { // Basic validation on input to provide immediate feedback var id = this.id; var value = this.value; var numValue = parseFloat(value); var errorElement = document.getElementById('error-' + id); errorElement.innerText = ''; errorElement.classList.remove('visible'); this.style.borderColor = '#ccc'; // Reset if (value !== '') { if (isNaN(numValue)) { errorElement.innerText = 'Enter a number.'; errorElement.classList.add('visible'); this.style.borderColor = '#dc3545'; } else { var min = null, max = null; if (id === 'correlation') { min = -1; max = 1; } else if (id.includes('volatility') || id === 'targetRisk') { min = 0; } else if (id.includes('Return')) { min = -100; max = 100; } if (min !== null && numValue max) { errorElement.innerText = `Max: ${max}`; errorElement.classList.add('visible'); this.style.borderColor = '#dc3545'; } } } // Calculate only if all inputs are currently valid looking var allInputsValid = true; var allInputElements = document.querySelectorAll('#calculator-form input[type="number"]'); for(var j=0; j < allInputElements.length; j++){ if(!validateInput(allInputElements[j].id, null, null, true)) { // Allow empty for this check allInputsValid = false; break; } } if(allInputsValid) { calculatePortfolioWeights(); } else { // If any input is invalid, clear results for safety document.getElementById('main-result-weight').innerText = '–'; document.getElementById('optimalWeightAsset1').innerText = '–'; document.getElementById('optimalWeightAsset2').innerText = '–'; document.getElementById('portfolioExpectedReturn').innerText = '–'; if (window.myPortfolioChart) { window.myPortfolioChart.destroy(); window.myPortfolioChart = null; var canvas = document.getElementById('portfolioChart'); var context = canvas.getContext('2d'); context.clearRect(0, 0, canvas.width, canvas.height); } } }); } });