Stock Average Price Calculator
Bought the same stock at different prices? Your real cost basis is the weighted average of every lot — not the simple midpoint. See it, your breakeven, and exactly how many shares it takes to average down to any target.
Your inputs
Your lots
| Lot | Shares | Buy price | Cost | Share of position |
|---|
The math: weighted, not simple, average
Your average cost is total dollars paid ÷ total shares owned. The price of each lot is weighted by how many shares you bought at it — a 1,000-share lot at $30 drags the average far more than a 10-share lot at $50. The simple midpoint of your buy prices is only correct when every lot is the same size.
Breakeven ≈ average (before commissions)
Shares to reach target = (total cost − target × total shares) ÷ (target − buy price)
Worked example
100 shares at $50 ($5,000) and 100 shares at $30 ($3,000): $8,000 ÷ 200 shares = $40.00 average. At a $35 market price the position is worth $7,000 — a −$1,000 (−12.5%) unrealized loss, and you need $40 to break even. To average down to $38 buying at $25: (8,000 − 38×200) ÷ (38 − 25) = 400 ÷ 13 ≈ 30.77 shares.
Averaging down: the honest tradeoff
- It lowers your breakeven. Every share bought below your average pulls the average down — mathematically certain.
- It concentrates risk. You're putting more money into a stock that's already losing you money. Position sizing still applies: know your max before you start.
- It only works buying below the target. If the buy price is above your target average, new shares push the average up. The goal mode refuses that trade and tells you why.
- Commissions and taxes are ignored here. Use the stock profit calculator for commission-adjusted breakeven, and remember your broker tracks lots separately (usually FIFO) for tax.