Position cost
Average-down calculator
What does averaging down do to your cost basis? Add each buy below to see the new per-share cost, the breakeven sell price, and how far the current price is from it.
Average cost per share
11.48
Total 1,800 shares · cost basis 20,660
Shares
1,800
Total cost
20,660
Breakeven sell
11.48
Floating P&L
-1,220.00 （-5.91%）
Rise still needed 6.28%
P&L at other prices
| Move | Price | P&L | P&L % |
|---|---|---|---|
| -25.0% | 8.10 | -6,080.00 | -29.43% |
| -20.0% | 8.64 | -5,108.00 | -24.72% |
| -15.0% | 9.18 | -4,136.00 | -20.02% |
| -10.0% | 9.72 | -3,164.00 | -15.31% |
| -5.0% | 10.26 | -2,192.00 | -10.61% |
| +0.0% | 10.80 | -1,220.00 | -5.91% |
| +5.0% | 11.34 | -248.00 | -1.20% |
| +10.0% | 11.88 | +724.00 | +3.50% |
| +15.0% | 12.42 | +1,696.00 | +8.21% |
| +20.0% | 12.96 | +2,668.00 | +12.91% |
| +25.0% | 13.50 | +3,640.00 | +17.62% |
The averaging-down formula
After several buys, the per-share cost basis is Σ(qty × price × (1 + buy fee)) ÷ total shares. Buy-side fees raise the basis; selling costs another round of commission plus stamp tax.
The true breakeven is not the average cost itself but average cost ÷ (1 − sell-side fee), where the sell-side fee is commission plus stamp tax (A-share stamp tax is currently 0.05% of the sale, charged on sells only). Fees default to 0 — fill in your own rates.
Averaging down cuts cost, not risk
Buying the dip pulls your basis toward the latest price, so a smaller rebound gets you back to breakeven. The trade-off is a larger position in a single name. Before adding, separate a planned laddered entry from panic averaging.
Frequently asked
How is the new cost basis computed?
New basis = (old qty × old cost + new qty × buy price) ÷ (old qty + new qty). With commission, each buy's turnover is multiplied by (1 + fee rate) first. The tool stacks as many lots as you add.
Why is breakeven higher than the average cost?
Selling costs commission plus stamp tax, so the net proceeds must clear those fees. A-share stamp tax is 0.05% of the sale, charged on the sell side only — enter it under 'sell stamp tax'.
What if quantity or price is 0 / negative?
Quantity must be positive and price non-negative — invalid rows are flagged and the computation stops rather than producing a wrong basis.
Can it handle three or more buys?
Yes. Press 'add another buy' and every row is merged into one consolidated position.
Everything is computed locally from your inputs — no market data is fetched. Use your broker's actual commission and tax rates. Estimates only, not investment advice.