Stock Average Calculator
To calculate your stock average cost, sum (shares × price) across every purchase and divide by total shares: Avg = Σ(s × p) / Σs. This page plots each purchase as a dot along the price line, with the green dashed line marking your weighted-average cost basis.
Quick Conversion
Formula: Avg = Total cost / Total shares
DCA Purchase Plot
All purchases (12)
| Date | Shares | Price | Cost | vs Avg | |
|---|---|---|---|---|---|
| 2025-01 | 5.0000 | $588.00 | $2940.00 | $-34.08 | |
| 2025-02 | 5.0000 | $605.00 | $3025.00 | $-17.08 | |
| 2025-03 | 5.0000 | $595.00 | $2975.00 | $-27.08 | |
| 2025-04 | 5.0000 | $540.00 | $2700.00 | $-82.08 | |
| 2025-05 | 5.0000 | $585.00 | $2925.00 | $-37.08 | |
| 2025-06 | 5.0000 | $615.00 | $3075.00 | $-7.08 | |
| 2025-07 | 5.0000 | $632.00 | $3160.00 | +$9.92 | |
| 2025-08 | 5.0000 | $645.00 | $3225.00 | +$22.92 | |
| 2025-09 | 5.0000 | $660.00 | $3300.00 | +$37.92 | |
| 2025-10 | 5.0000 | $642.00 | $3210.00 | +$19.92 | |
| 2025-11 | 5.0000 | $668.00 | $3340.00 | +$45.92 | |
| 2025-12 | 5.0000 | $690.00 | $3450.00 | +$67.92 |
DCA strategy presets
DCA outcome table
| Buys | Total $ | Avg if prices [10,11,9,12,8...] |
|---|---|---|
| 2 | $2,000 | $10.73 |
| 3 | $3,000 | $11.10 |
| 5 | $5,000 | $10.59 |
| 8 | $8,000 | $9.83 |
| 10 | $10,000 | $10.16 |
| 12 | $12,000 | $10.11 |
| 15 | $15,000 | $9.81 |
| 20 | $20,000 | $9.87 |
Want to see profit/loss on these positions? See Stock Profit Calculator →
Formula
AvgCost = Σ(shares_i × price_i) / Σ shares_iWorked: 5 sh @ $100 + 5 sh @ $120 → cost = $500 + $600 = $1100, shares = 10, Avg = $110/share.
From Benjamin Graham to Robinhood: the long history of Dollar Cost Averaging
In 2026, a 27-year-old software engineer auto-DCAs $500/month into VTSAX through her employer's 401(k). She has no idea she is following a strategy with a hundred-year history. This page visualises every purchase as a dot on the price line — so DCA stops being abstract math and becomes a chart she can read at a glance.
The Sixteenth Amendment's 1913 Internal Revenue Act introduced the modern US income tax and forced taxpayers to track cost basis on stock and bond sales. The average-cost convention for mutual fund shares first appeared in 1950s Treasury decisions; today IRS Pub 550 codifies it as one of four allowed cost basis methods (the others being FIFO, LIFO, and specific-share identification).
Benjamin Graham coined the term "Dollar Cost Averaging" in The Intelligent Investor (1949) — the book Warren Buffett calls "the best book on investing ever written." Graham's case for DCA was behavioral: most investors cannot stomach lump-sum investing at market peaks, and the discipline of regular contribution removes timing anxiety.
Harry Markowitz's 1952 Journal of Finance paper formalized modern portfolio theory and introduced the mean-variance framework. DCA implicitly assumes the variance structure of the asset matters — buying through volatility lowers your effective cost. Markowitz, William Sharpe, and Merton Miller shared the 1990 Nobel Prize.
Michael Jensen's 1968 Journal of Finance paper "The Performance of Mutual Funds in the Period 1945-1964" used DCA as the implicit benchmark when measuring fund alpha. Jensen showed that on a risk-adjusted basis, the average mutual fund underperformed a simple DCA buy-and-hold strategy net of fees — a finding that launched the index-fund revolution led by Jack Bogle (Vanguard 500 Index Fund, 1976).
Frederick Macaulay's 1938 NBER monograph on bond duration introduced the weighted-time framework that underlies DCA cost-basis math. The same logic — weighting payments by their share of total — that gives Macaulay duration for a bond gives the average cost basis for a DCA stock position.
By 2026, the SEC's Regulation BI requires brokers to consider DCA as a low-cost alternative before recommending lump-sum investments. Robinhood, Fidelity, Schwab, and M1 Finance all support fractional-share auto-DCA down to $1 per purchase. Crypto exchanges like Coinbase and Kraken added auto-DCA in 2019 and 2021 respectively. The strategy Graham popularized in 1949 has become the default for the entire millennial and Gen Z investing cohort.
How to use the DCA visualizer
- Pick a preset or start blank. SPY 12-mo / TSLA buy-the-dip / BTC quarterly / AAPL 3-yr.
- Add each purchase. Enter date, shares, and price. The dot appears on the chart immediately.
- Read the dashed line. Green dashed = your weighted average. Below = wins, above = losers.
- Check the lot table. Each purchase shows its vs-average delta in green or red.
- Save the cost basis. Bookmark for tax-lot tracking; replay scenarios from history.
What DCA investors say
“I have been DCAing into VTSAX every Friday since 2017. The visualizer is the first tool that shows my buys color-coded by above/below average — the green dots from 2020 March really pop, and the red dots from late 2021 look painful. Beautiful UX.”
“I used this to backtest a TSLA buy-the-dip strategy against straight monthly DCA. The size-of-dot encoding by share count is genius — I can see at a glance which buys mattered most to the cost basis.”
“I show this tool to every client who asks about lump sum vs DCA. The visual is more persuasive than any spreadsheet. Vanguard's 2012 study makes a lot more sense after you SEE the dots cluster around the average.”
“The BTC quarterly preset is exactly my strategy. Seeing my 2024 Q3 buy at $60k as a green dot and my Q4 buy at $94k as a red dot was sobering. Tool saved me from chasing the rally — sticking with the quarterly cadence wins long term.”
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