Stock Average Calculator — Weighted Average Buy Price

When you buy a stock at multiple prices over time, your average buy price determines whether you’re profitable, not your last buy. The Stock Average Calculator weighs each purchase by quantity and gives you the true cost basis, helping you decide whether to hold, average down, or exit.

Stock Average Calculator

Compute the average buy price across multiple purchases of the same stock — essential for averaging-down strategies.

Average cost per share

Average Buy Price–
Total Shares–
Total Investment–
Highest Buy Price–
Lowest Buy Price–

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Why Average Price Matters

Suppose you bought 100 shares at $50 and 50 more at $40. Your average isn’t $45 (the midpoint) — it’s $46.67, because you own twice as many of the higher-priced lot. Most retail investors mis-estimate this and make wrong hold/exit decisions.

The Formula

Average = Σ (Qtyi × Pricei) / Σ Qtyi

It’s a weighted mean. Each lot contributes proportionally to your average based on its quantity.

Worked Example

Example: 100 shares @ $50 = $5,000. 50 shares @ $40 = $2,000. Total: 150 shares, $7,000 invested. Average = 7,000 / 150 = $46.67/share. To break even, the stock needs to cross $46.67.

Averaging Down vs Doubling Down

  • Average down rationally when fundamentals are intact and price has dropped due to market sentiment.
  • Don’t average down when the original thesis is broken — you’re throwing good money after bad.
  • Position sizing matters — averaging down increases concentration risk in a single stock.
  • Set a hard stop on how many times you’ll average down (typically 2–3 max).

Frequently Asked Questions

Should I always average down on a falling stock?▾
No — only if the fundamentals are still intact. If earnings are deteriorating, debt is rising, or the moat is gone, averaging down compounds the loss.
How does this differ from dollar-cost averaging?▾
DCA is buying fixed dollar amounts at regular intervals regardless of price (a strategy). This calculator just tells you the result — your average cost basis — after any pattern of buys.
Are brokerage and taxes included?▾
No — the calculator shows pure share-based average. Add brokerage and STT/STCG to your effective cost basis manually if you want exact P&L.
Can I include sells too?▾
This calculator is for averaging buys only. For full P&L with buy/sell pairs, use the Stock Return Calculator.

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