Stock Average Calculator
Average cost per share across buys plus profit or loss at the current price.
What it does
Buying the same stock twice blends into one average cost: every dollar ever paid divided by every share ever received. That average is the breakeven line where the position turns from red to green.
The tool above takes two buys with share counts and prices plus the current quote. It returns the average, the total invested, and the unrealized gain or loss with percent.
Averaging down tempts after drops because fresh cheap shares drag the average toward the market. The math works, but concentration risk grows with it: more money now rides the same thesis that already fell once.
Tax lots complicate real selling. Brokers track FIFO, LIFO, or chosen lots, and wash sales can defer losses. The average here guides decisions while the broker statement governs taxes.
How to use
- Enter shares and price for each buy exactly as filled.
- Enter the current market price.
- Read the average as the breakeven to beat.
- Compare position size against your risk limits before adding.
Formula
- shares x price
- Cash paid in each buy, summed.
- total shares
- All shares held across buys.
- current - average
- Per share gain or loss, signed.
Three or more buys extend the same way: sum all cash, divide by all shares. Stock splits adjust history retroactively, so split era prices need care.
Worked example
Example: 100 at $50, then 100 at $30, now $35
First buy 100 shares at 50, second 100 at 30, quote 35.
- Cash in: 100 x 50 + 100 x 30 = 5,000 + 3,000 = $8,000.
- Shares: 200. Average: 8,000 / 200 = $40.00.
- Per share: 35 - 40 = -$5.00.
- Position: -$5.00 x 200 = -$1,000.00 (-12.5%).
Reference table
| Second buy at | Average | At $35 quote |
|---|---|---|
| $40 | $45.00 | -$2,000.00 (-22.22%) |
| $30 | $40.00 | -$1,000.00 (-12.50%) |
| $20 | $35.00 | $0.00 (breakeven) |
| $10 | $30.00 | +$1,000.00 (+16.67%) |
Limits
- Raw average only. Fees, spreads, and taxes excluded.
- Two buys modeled. More lots need summing first.
- Splits and dividends adjust real history.
- Paper gain is not cash until sold.
Common mistakes
- Averaging down a broken thesis to zero.
- Forgetting fees that lift the true average.
- Reading breakeven as a sell signal by itself.
- Sizing the second buy bigger than the plan allows.
- Mixing pre and post split prices.
Try it yourself
Quick checks. Answers sit tucked under each question.
50 at $20 plus 50 at $10. Average?
(1,000 + 500) / 100 = $15.00.
Position at $18 quote?
(18 - 15) x 100 = +$300.00 (+20%).
Questions
What is averaging down?
Buying more after a fall to lower average cost. It cuts breakeven but raises exposure.
Does average include fees?
True average should. Add commissions to cash paid before dividing.
How do splits affect average?
A 2 for 1 split halves price and doubles shares. Averages adjust the same way.
What is wash sale risk?
Claiming a loss then rebuying within 30 days can defer it for US taxes.
Should I average a falling stock?
Only with fresh reasons, sized small. Falling prices alone are not analysis.
Where is breakeven?
The average cost. Above it the position profits before fees and tax.