How to Calculate Your Portfolio Rate of Return

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Portfolio Rate of Return Calculator

(Total deposits minus total withdrawals during the period)

function calculateReturn() { var initial = parseFloat(document.getElementById('initialValue').value); var final = parseFloat(document.getElementById('finalValue').value); var cash = parseFloat(document.getElementById('netCashFlow').value); var resultDiv = document.getElementById('returnResult'); if (isNaN(initial) || isNaN(final) || isNaN(cash)) { resultDiv.style.display = 'block'; resultDiv.style.backgroundColor = '#f8d7da'; resultDiv.innerHTML = 'Please enter valid numeric values in all fields.'; return; } // Simple Dietz Method: Approximation of time-weighted return // Gain = End – Start – Net Cash Flow // Average Capital = Start + (Net Cash Flow / 2) var gain = final – initial – cash; var averageCapital = initial + (cash / 2); if (averageCapital === 0) { resultDiv.style.display = 'block'; resultDiv.style.backgroundColor = '#f8d7da'; resultDiv.innerHTML = 'Starting value and cash flow cannot result in zero capital.'; return; } var rateOfReturn = (gain / averageCapital) * 100; resultDiv.style.display = 'block'; resultDiv.style.backgroundColor = '#d4edda'; resultDiv.style.color = '#155724'; resultDiv.innerHTML = '

Your Portfolio Performance

' + " + rateOfReturn.toFixed(2) + '%' + 'Total Gain/Loss: $' + gain.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}) + ''; }

Understanding Your Portfolio Rate of Return

Calculating the performance of your investments is crucial for determining if you are on track to meet your financial goals. While checking your balance is a start, the "Rate of Return" tells you how efficiently your capital is working for you, accounting for the timing and size of your deposits.

The Calculation Method: Simple Dietz

This calculator utilizes the Simple Dietz Method. This is a common formula used by individual investors to estimate the time-weighted return of a portfolio when cash flows (deposits or withdrawals) occur. It prevents your performance percentage from being distorted by large sums of money moving in or out of the account.

How to Use This Calculator

  1. Starting Portfolio Value: Enter the total value of your investments at the beginning of the period you are measuring (e.g., January 1st).
  2. Ending Portfolio Value: Enter the total value of your investments at the end of the period (e.g., December 31st).
  3. Net Contributions/Withdrawals: This is the total amount of "new" money you added to the account, minus any money you took out. If you withdrew more than you deposited, enter a negative number.

Real-World Example

Imagine you started the year with $10,000. Over the year, you deposited a total of $2,000 into your brokerage account. At the end of the year, your account is worth $13,500.

  • Initial Value: $10,000
  • Final Value: $13,500
  • Net Cash Flow: $2,000
  • Calculation: Your raw gain is $1,500 ($13,500 – $10,000 – $2,000).
  • Result: Your rate of return is approximately 13.64%.

Why Net Contributions Matter

Without accounting for the $2,000 deposit in the example above, it might look like your portfolio grew by 35% ($10,000 to $13,500). However, $2,000 of that growth came from your own pocket, not from investment gains. The Rate of Return calculation isolates the actual performance of the market and your asset allocation.

Simple Return vs. Time-Weighted Return

While the Simple Return (Gain / Initial Value) is easy to calculate, it fails when you add money mid-year. The Time-Weighted Return (which this calculator approximates) is the industry standard for comparing your performance against benchmarks like the S&P 500, as it removes the effects of the timing of your deposits and withdrawals.

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