Stock Cost Average Calculator
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Stock Cost Average Calculator
Your Average Cost Per Share
$0.00
Understanding Stock Cost Averaging
The Stock Cost Average Calculator helps investors determine their average purchase price per share for a stock, considering multiple buys at different prices and quantities. This is a fundamental calculation for understanding your investment's performance and for tax purposes (like calculating capital gains or losses when selling).
How it works:
- The calculator takes your purchase history, which includes the number of shares bought and the price per share for each transaction.
- For each purchase, it calculates the Total Cost (Shares * Price Per Share).
- It then sums up the Total Cost of all purchases to get the Grand Total Cost.
- It also sums up the Total Number of Shares purchased across all transactions.
- Finally, it divides the Grand Total Cost by the Total Number of Shares to arrive at the Average Cost Per Share.
The Formula:
Average Cost Per Share = (Sum of (Shares Bought * Price Per Share) for all purchases) / (Sum of Shares Bought for all purchases)
Why is this important?
Knowing your average cost per share is crucial for:
- Performance Tracking: Easily compare your current stock price against your average cost to see your unrealized profit or loss.
- Dollar-Cost Averaging (DCA): This calculation is the direct result of implementing a DCA strategy, where you invest a fixed amount of money at regular intervals, regardless of the stock price. This calculator helps you track the outcome of your DCA efforts.
- Tax Reporting: When you sell shares, you'll need your cost basis (which is often your average cost per share) to calculate capital gains or losses for tax purposes.
Use this calculator regularly to keep your investment records accurate and make informed decisions.
function calculateAverageCost() {
var purchaseHistoryInput = document.getElementById("purchaseHistory").value;
var totalCost = 0;
var totalShares = 0;
if (purchaseHistoryInput.trim() === "") {
document.getElementById("averageCostPerShare").innerText = "$0.00";
return;
}
var purchases = purchaseHistoryInput.split(',');
var validEntries = [];
for (var i = 0; i < purchases.length; i++) {
var trimmedEntry = purchases[i].trim();
if (trimmedEntry) {
validEntries.push(trimmedEntry);
}
}
if (validEntries.length % 2 !== 0) {
alert("Please ensure your purchase history is in pairs of Shares and Price Per Share, separated by commas. e.g., 10,50.50, 25,52.00");
document.getElementById("averageCostPerShare").innerText = "$0.00";
return;
}
for (var i = 0; i < validEntries.length; i += 2) {
var shares = parseFloat(validEntries[i]);
var pricePerShare = parseFloat(validEntries[i + 1]);
if (isNaN(shares) || isNaN(pricePerShare) || shares < 0 || pricePerShare 0) {
averageCost = totalCost / totalShares;
}
document.getElementById("averageCostPerShare").innerText = "$" + averageCost.toFixed(2);
}