DCA Calculator

Backtesting a dollar-cost-averaging strategy by hand means pulling historical prices, splitting your investment by the chosen interval, summing the units bought at each price point, and comparing to a lump-sum buy at the start. Half a day of spreadsheet work to answer a yes/no question.

Provide the asset, the period, the contribution amount, and the cadence (weekly, biweekly, monthly), and the calculator returns total invested, total units accumulated, average buy price, current value, and the difference versus a one-time buy at the start of the period. The same numbers a careful spreadsheet would produce, computed in seconds.

Worth doing before committing to a real DCA plan, especially in volatile markets where the gap between DCA and lump-sum can swing in either direction depending on the entry timing. Past results don't guarantee future ones — but they at least give you a feel for the strategy's behavior.

The core math is straightforward and worth knowing even if you let the calculator do the work. For each interval (date_i with price_i), units bought = contribution / price_i. Sum the units across all intervals to get total units. Average buy price = total invested / total units, which is harmonically weighted toward intervals when the price was lower (more units bought, more weight in the average). Current value = total units × current price. The lump-sum comparison invests the entire amount on day one at the start price, so total units = total invested / start price; current value = those units × current price.

Worked example over a hypothetical 12-month period: contribute $500/month, prices range from $30 to $50 with a $40 closing price. DCA invested $6,000 across 12 months and ended with units worth, say, $6,800 at average price $35. Lump-sum bought $6,000 worth at $50 (the start), which is 120 units; at the $40 close, those are worth $4,800. In this scenario DCA wins because the price fell and recovered partway. Reverse the price path (start at $30, end at $50) and lump-sum wins decisively because every later DCA contribution buys at a higher price than day one.

What the calculator can't capture is the part of DCA that actually drives most people's choice — emotional steadiness during drawdowns. A lump-sum investor watching a 30% portfolio drawdown two weeks after deploying $50,000 has a meaningfully harder time staying invested than a DCA investor whose first month was only $4,000. The "wrong" choice on expected returns can be the right choice for behavioral reasons. The calculator shows the math; you decide whether expected-value math is the right frame.

A lurking issue: backtests overstate what DCA "would have done" because they exclude survivorship bias. If you DCA into BTC over the past five years, the calculator shows great returns. If you'd DCA'd into a smaller altcoin in 2021 that since collapsed, the calculator would show catastrophic returns — and that's the experience of a meaningful number of investors who picked wrong. Past asset performance doesn't predict future asset performance, especially in crypto where today's leader can be tomorrow's zombie token.