Stock Average Calculator

Find your average cost per share across multiple stock purchases at different prices.

≈$ What is a Stock Average Calculator?

A stock average calculator computes your weighted average cost per share when you have purchased the same stock at multiple different prices. It answers the fundamental investor question: “Given all my buy orders, what did I effectively pay per share on average?” This number is your cost basis — the benchmark against which you measure profit or loss.

The formula is straightforward but different from a simple average: Weighted Average Cost = Total Money Invested ÷ Total Shares Held. Total money invested = sum of (shares bought × price paid) across every purchase. This weighted average correctly reflects that a purchase of 500 shares at €50 matters ten times more than a purchase of 50 shares at €80 when computing the true average.

Averaging down is a popular strategy where an investor buys more shares as the price falls, deliberately lowering their average cost. The logic: if the stock eventually recovers to its original price, the investor now profits on all their shares, not just the first batch. This calculator lets you model exactly how many shares you would need to buy at a lower price to reach a target average. The opposite — averaging up — occurs when you add to a winning position, raising your average cost but typically with a higher conviction in further gains.

Dollar Cost Averaging (DCA) is a disciplined investing strategy where you invest a fixed amount (e.g., €500/month) regardless of the stock price. Because you buy more shares when the price is low and fewer when it is high, DCA naturally produces a weighted average cost below the arithmetic mean of the prices you paid at. This calculator shows you your exact DCA-weighted average by entering each monthly purchase as a separate row.

📐 Formula

Average Cost = ∑(Shares_i × Price_i) ÷ ∑Shares_i

Shares_i = number of shares in purchase i

Price_i = price paid per share in purchase i

Total Invested = ∑(Shares_i × Price_i)

Total Shares = ∑Shares_i

Example: Buy 1: 100 shares @ €200. Buy 2: 150 shares @ €160. Avg = (100×200 + 150×160) ÷ 250 = 44,000 ÷ 250 = €176

📖 How to Use This Calculator

Steps

Enter each purchase in the rows provided — type the number of shares and the price per share for that transaction.

Add more rows by clicking “+ Add Purchase”. Click × on any row to remove it. You can track as many purchases as needed.

Click Calculate to see your weighted average cost per share, total shares, total money invested, and the price range from lowest to highest purchase price.

💡 Example Calculations

Example 1 — Averaging Down on a Falling Stock

Buy 1: 100 shares @ €500. Buy 2: 200 shares @ €350.

Total invested = 100×500 + 200×350 = 50,000 + 70,000 = €120,000

Total shares = 300. Average = 120,000 ÷ 300 = €400

Average cost = €400. Break-even at €400 (was €500). You need the stock to recover 14.3% instead of 42.9%.

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Example 2 — 3-Month DCA

Invest €1,000/month: Month 1 @ €100, Month 2 @ €80, Month 3 @ €120

Shares: Month 1 = 10, Month 2 = 12.5, Month 3 = 8.33. Total = 30.83 shares.

Total invested = €3,000. Average = 3,000 ÷ 30.83 = €97.30

DCA average = €97.30 vs simple average of €100. DCA produces a lower average because you automatically buy more shares at the dip.

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Example 3 — Four Purchases (Full Portfolio Lot)

100 shares @ ₹1,200 · 50 shares @ ₹1,050 · 200 shares @ ₹900 · 75 shares @ ₹1,100

Total = 100×1200 + 50×1050 + 200×900 + 75×1100 = 120,000 + 52,500 + 180,000 + 82,500 = ₹435,000

Total shares = 425. Average = 435,000 ÷ 425 = ₹1,023.53

Weighted average = ₹1,023.53. Price range: ₹900 – ₹1,200. The large 200-share lot at ₹900 pulls the average down significantly.

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Example 4 — After a 2:1 Stock Split

Original: 200 shares @ €400 average. Stock splits 2:1.

After split: 400 shares @ €200 each. Total invested unchanged: €80,000.

New average = 80,000 ÷ 400 = €200. Enter this as a single row in the calculator.

Post-split average cost = €200 per share. Total investment and break-even (in value terms) are unchanged.

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Frequently Asked Questions

How do you calculate the average cost per share?

Average cost per share = Total Money Invested ÷ Total Shares Held. Total money invested = Σ(shares_i × price_i) across all purchases. Example: Buy 100 shares at ₹200 and 150 shares at ₹160: Total cost = 100×200 + 150×160 = 20,000 + 24,000 = 44,000. Total shares = 250. Average cost = 44,000 ÷ 250 = ₹176 per share.

What is averaging down in stocks?

Averaging down is the strategy of buying more shares of a stock as its price falls, thereby lowering your average cost per share. Example: you bought 100 shares at ₹500 (average = ₹500). If you buy another 100 shares at ₹300, your new average = (100×500 + 100×300)/200 = ₹400. The strategy works if the stock recovers; it increases losses if it falls further.

What is dollar cost averaging (DCA)?

Dollar cost averaging (DCA) is investing a fixed rupee/dollar amount at regular intervals regardless of price. Because you buy more shares when prices are low and fewer when high, DCA produces an average cost below the simple average price. For example, investing ₹10,000/month when prices are ₹100, ₹80, and ₹120 buys 100, 125, and 83.3 shares — total 308.3 shares for ₹30,000 = ₹97.30/share, below the simple average of ₹100.

How do I calculate my break-even price after averaging down?

Your break-even price is your average cost per share. If you sell all shares at exactly your average cost, you neither gain nor lose (excluding taxes and brokerage fees). This calculator shows your average cost — that is your break-even. To profit, the stock must trade above that price when you sell.

What is cost basis and why does it matter for taxes?

Cost basis is the total original value of your investment: total shares × average cost per share. When you sell shares, capital gain = (sale price − cost basis per share) × shares sold. In India, short-term capital gains (held < 1 year for equity) are taxed at 15%; long-term (held > 1 year) at 10% above ₹1 lakh. Accurate cost basis tracking minimizes tax liability.

Should I average down on a falling stock?

Averaging down can be a sound strategy if you are confident in the company's long-term fundamentals and the price drop is due to market sentiment rather than deteriorating business quality. It is risky if the company faces structural problems — averaging down on a failing business increases losses. Always assess the reason for the price decline before adding to a losing position.

What is the difference between average cost and FIFO for tax purposes?

Average cost uses the weighted mean of all purchase prices. FIFO (First In, First Out) assumes you sell the shares you bought earliest first. In a rising market, FIFO produces higher cost basis on early sales (potentially lower gains). In a falling market, FIFO produces lower cost basis (higher gains). India's tax rules for mutual funds use average cost; for direct stock, FIFO is commonly assumed. Consult a tax advisor for your specific situation.

How does a stock split affect my average cost?

A stock split increases your shares and proportionally decreases your average cost. For a 2:1 split: your shares double and your cost per share halves, but total investment stays the same. Example: 100 shares at ₹1,000 average cost → after 2:1 split → 200 shares at ₹500 average cost. Update this calculator by doubling shares and halving prices in all purchase rows.

Can I use this for ETFs and mutual funds?

Yes. The weighted average cost formula is identical for ETFs, mutual funds (units × NAV), or any investment where you make multiple purchases at different prices. For mutual fund SIP calculations, enter each monthly purchase as a row. The resulting average NAV is your cost basis per unit.

What is the weighted average vs simple average price?

Simple average = (Price1 + Price2 + … + PriceN) ÷ N — weights each price equally regardless of quantity. Weighted average = Σ(shares_i × price_i) ÷ Σ(shares_i) — larger purchases influence the average more. For cost basis, the weighted average is always correct. If you buy 1 share at ₹100 and 1,000 shares at ₹50, the simple average is ₹75 but your true cost basis is just ₹50.05 per share.

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📌 Quick Tips

💡Your average cost is a weighted average — buying more shares at a lower price pulls your average down more than buying fewer shares. This is why 'averaging down' works better when you buy a larger quantity at the lower price.

💡Cost basis for tax purposes equals your average cost per share times the number of shares. When you sell, capital gain = (sale price − cost basis) × shares sold.

💡Dollar Cost Averaging (DCA) is the strategy of buying a fixed dollar amount (not a fixed number of shares) at regular intervals. DCA naturally buys more shares when prices are low and fewer when high — this calculator helps you see the resulting average price.

💡When a stock splits (e.g., 2-for-1), your number of shares doubles but your cost per share halves. Adjust your entries accordingly — the total cost remains the same.

💡Add as many purchase rows as needed. Click the × button to remove a row; the first row cannot be deleted.