Stock Average Calculator
Stock Average Calculator
Your Purchases
Fractional shares are fine. Leave fees at $0 for commission-free brokers.
Average Down / Up Planner
Your Results
To reach a $38.00 average
Buy 113 shares at $30.00 — about $3,390.00 of new capital. Your position grows to 313 shares ($11,890.00 invested).
If you buy more at $30.00
| Add | Cost | New Avg | To B/E |
|---|---|---|---|
| +50 sh | $1,500.00 | $40.00 | +14.29% |
| +100 sh | $3,000.00 | $38.3333 | +9.52% |
| +200 sh | $6,000.00 | $36.25 | +3.57% |
| +400 sh | $12,000.00 | $34.1667 | ✓ |
Based on your results — what to do next:
What do you net if you sell from here?
With a $42.50 breakeven on 200 shares, see your after-tax profit at any sell price — short-term vs. long-term rates.
Put this loss to work
Your $1,500.00 unrealized loss could offset other gains — watch the 30-day wash-sale rule if you average down.
Automate it instead of timing dips
Instead of lump-sum averaging down with $3,390.00, model spreading that money over regular monthly buys.
A stock average calculatorfinds your average cost per share when you buy the same stock at different prices. It divides the total amount invested by the total shares owned. This version also adds fees to show your true breakeven, shows your unrealized gain or loss at today's price, and solves for the exact number of shares you need to buy to average down (or up) to a target price.
How the Stock Average Is Calculated
① Average price per share
Avg = Σ(Pᵢ × Qᵢ) ÷ ΣQᵢ
Breakeven with fees = (Σ(Pᵢ × Qᵢ) + ΣFees) ÷ ΣQᵢ
② Shares needed to reach a target average
x = (C − T × S) ÷ (T − P)
Only solvable when the buy price is on the far side of the target (P < T to average down).
③ Move needed to break even
Breakeven % = (Avg − Current Price) ÷ Current Price × 100
| Variable | Meaning |
|---|---|
| Pᵢ, Qᵢ | Price and share count of each purchase |
| C | Total cost basis today (including fees) |
| S | Shares currently owned |
| T | Target average price |
| P | Price of the next purchase |
Worked Example — three buys, stock now at $35
- 100 sh @ $50 + 50 sh @ $40 + 50 sh @ $30 = $8,500 for 200 shares
- Average price: $8,500 ÷ 200 = $42.50
- At $35 the position is worth $7,000, an unrealized loss of −$1,500 (−17.6%)
- The stock must rise 21.4% to get back to $42.50
- To average down to $38 buying at $30: (8,500 − 38 × 200) ÷ (38 − 30) = 112.5 → 113 shares ≈ $3,390
💡 Pro-Tip
Averaging down lowers your breakeven, not your risk.In the example, $3,390 of new money cuts the breakeven from $42.50 to $38, but it also makes the stock a bigger share of your portfolio. Before you buy more, ask whether you would buy this stock today at this price if you owned none of it. If the answer is no, a lower average won't fix the underlying problem. Many investors cap any single stock at 5–10% of their portfolio, including any shares added while averaging down.
Stock Average Calculator FAQ
How do you calculate the average price of a stock?
Add up the total dollars spent on every purchase (price × shares for each lot) and divide by the total number of shares you own. Example: 100 shares at $50, 50 at $40, and 50 at $30 cost $8,500 for 200 shares, so the average price is $42.50 per share.
How many shares do I need to buy to average down?
Use x = (Current Cost − Target × Current Shares) ÷ (Target − Buy Price). If you own 200 shares costing $8,500 and want a $38 average by buying at $30, you need (8,500 − 7,600) ÷ 8 = 112.5, so 113 shares costing about $3,390.
Can I average down to any price I want?
No. Your new average is always between your old average and the new buy price. To reach a target average, you must buy below that target. If the stock is at $30, you can never average down to $29 no matter how many shares you buy.
Should I include commissions in my average cost?
Yes. For tax purposes, commissions and fees are added to your cost basis, so your real breakeven is (total cost + fees) ÷ shares. This calculator shows both the plain average and the fee-adjusted breakeven.
Does averaging down trigger the wash-sale rule?
Buying more shares does not by itself trigger a wash sale. But if you sell shares at a loss within 30 days before or after buying the same stock, the loss is disallowed and added to the basis of the new shares. Plan loss harvesting and averaging down so they are more than 30 days apart.
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