DCA Calculator

The core of dollar-cost averaging is a single ratio: your average cost per unit equals total money invested divided by total units acquired. Because you invest a fixed dollar amount each period, the number of units you receive changes with the price. $100 buys 1.25 units at $80 but only 0.8 units at $125, so cheap periods contribute more units to the denominator and expensive periods contribute fewer. Work through a four-month plan of $100 per month at prices of $100, $80, $125, and $100. The units acquired are 1.0, 1.25, 0.8, and 1.0, for a total of 4.05 units from $400 invested. Your average cost is 400 / 4.05 ≈ $98.77 per unit. Compare that with the simple arithmetic average of the four prices, (100 + 80 + 125 + 100) / 4 = $101.25. The DCA average is lower, and this is not a coincidence. Mathematically, when you invest equal dollar amounts, your average cost is the harmonic mean of the purchase prices: n divided by the sum of the reciprocals of each price. The harmonic mean is always less than or equal to the arithmetic mean, with equality only when every price is identical. In plain terms, a fixed-dollar schedule automatically overweights cheap purchases and underweights expensive ones, with no timing skill, forecasts, or willpower required. The more the price fluctuates around its average, the wider the gap between the two means, so volatility itself works in favor of your average cost.

// Four monthly buys of $100 each
const prices = [100, 80, 125, 100];
const units = prices.map((p) => 100 / p);      // [1.0, 1.25, 0.8, 1.0]
const totalUnits = 1.0 + 1.25 + 0.8 + 1.0;     // 4.05
const avgCost = 400 / totalUnits;              // ≈ 98.77 (harmonic mean)
const meanPrice = (100 + 80 + 125 + 100) / 4;  // 101.25 (arithmetic mean)
// avgCost < meanPrice whenever prices vary

If you already have the full amount in hand, the historical evidence is uncomfortable for DCA. Studies by Vanguard and others across US, UK, and Australian market history found that investing a lump sum immediately outperformed spreading it over 6 to 12 months in roughly two-thirds of rolling periods. The reason is simple: markets have trended upward more often than not, so every dollar waiting on the sidelines misses expected growth and any dividends along the way. On average, delay costs money. So why does DCA remain so popular? Because the two-thirds statistic hides what the other one-third feels like. Committing everything the week before a 30% drawdown is the scenario people actually fear, and DCA caps that regret: a schedule that keeps buying through the decline picks up cheap units instead. DCA is best understood as a risk-management and behavioral commitment device, not a return maximizer. It converts a paralyzing question, whether now is a good time to buy, into a routine you can automate and forget. There is also a case where the comparison is moot: most people invest from income, receiving money in monthly increments. Contributing each payday is effectively a series of small lump sums invested as early as possible, so the paycheck investor gets both properties at once. DCA tends to beat lump-sum specifically in markets that fall and then recover, or that chop sideways with high volatility, which is one reason the approach has such a strong following among crypto investors.

DCA has failure modes worth knowing before you rely on it. In a steadily rising market it systematically underperforms, because every later purchase is more expensive than the last: buying $100 monthly at prices of $100, $110, $120, and $130 yields about 3.512 units at an average cost near $113.91, worse than the $100 cost you would have locked in by investing all $400 on day one. The most damaging mistake is behavioral: stopping contributions during a crash. The entire mechanism depends on buying the cheap units near the bottom; if you pause when prices fall 40% and resume after recovery, you have kept the expensive purchases and skipped the discounted ones, inverting the strategy's logic. Automating transfers so that no monthly decision is required is the practical defense. Costs matter disproportionately at small sizes. A fixed $1 fee on a $50 purchase is a 2% loss before the asset moves at all; the same fee on a $500 purchase is 0.2%. When fees are fixed, buying less frequently in larger amounts usually nets out better. On thinly traded pairs, bid-ask spread and slippage act as an additional hidden fee on every single order. Finally, DCA is not a rescue plan for a bad pick. Averaging down into one failing company or token concentrates risk in something that may go to zero, and an asset that never recovers has no cheap units, only losses. The strategy's assumptions hold for broad, durable assets such as diversified index funds, not for any single position.

Fixed fee drag on small orders
  $1 fee on a $50 buy:   1 / 50  = 0.02   ->  2.0% lost before any price move
  $1 fee on a $500 buy:  1 / 500 = 0.002  ->  0.2% lost

Rising market example: $100/month at $100, $110, $120, $130
  units    = 1 + 0.9091 + 0.8333 + 0.7692 = 3.5117
  avg cost = 400 / 3.5117 ≈ $113.91   (vs $100 lump sum on day one)

Several relatives of standard DCA solve adjacent problems. DCA in reverse, selling a fixed dollar amount or a fixed fraction of a position at regular intervals, de-risks an exit the same way regular buying de-risks an entry. Retirees drawing down a portfolio and holders of concentrated positions use it to avoid selling everything at what turns out to be a local bottom. Value averaging targets a growth path for the portfolio rather than a fixed contribution. If your plan calls for the account to grow by $500 per month and markets fall, you contribute more than $500 to get back on track; if markets surge, you contribute less or even sell. This buys more aggressively at lows than plain DCA, but its cash demands are unpredictable: after a sharp drop, the required contribution can be several times your normal amount, which many budgets cannot absorb. A hybrid answers the lump-sum dilemma directly: invest half immediately, then DCA the remainder over 6 to 12 months. The expected return sits between the two pure approaches, and so does the worst case. Also note the interaction with rebalancing. Directing each new contribution to whichever asset class is furthest below its target weight rebalances the portfolio with fresh cash, often reducing or eliminating the need to sell, which can also mean fewer taxable events.

Every DCA purchase creates a separate tax lot: a quantity of units with its own date and cost basis. After three years of monthly buying you hold 36 lots, and which basis applies when you sell depends on your jurisdiction's rules. Some tax systems mandate or default to FIFO (first in, first out), others use an average-cost method across all units, and some allow you to identify specific lots at the time of sale; these choices can change the taxable gain on an identical sale by a wide margin. Rules for cryptocurrency in particular are still evolving in many countries. The practical takeaway is simple: keep a record of every purchase, including date, amount invested, units received, price, and fees, from the very first buy. Exchanges and brokers close, change owners, and prune old data; an export you keep yourself is far more durable. Because tax treatment differs so much by country and by asset type, consult a qualified tax professional before selling significant DCA-accumulated positions. This calculator uses a simplified linear price path, which makes it useful for building intuition about contribution size, frequency, and horizon, and inaccurate as a forecast, since real prices are anything but linear. Everything on this page, including the calculator itself, is educational content only and is not financial advice; past performance does not guarantee future results, and any investment can lose value. Use the numbers as a starting point for questions, not as a plan.