Short answer: Dollar-cost averaging (DCA) means buying the same dollar amount at regular intervals, whatever the price is doing. So $100 a month for 4 months while the price rises in equal steps from $20,000 to $26,000 buys about 0.01756 coins for $400, at an average cost of about $22,781.28 per coin — worth about $456.52 at the $26,000 end price. This free calculator runs that same math for your own amounts, prices and fees, and compares it with investing the whole sum at once.
Last updated: 1 November 2026 · Scenario estimate only — not financial advice.
How the math works
- One buy: coins from a buy = amount after fees ÷ price at that buy. A $100 buy at $20,000 gives 100 ÷ 20,000 = 0.005 coins.
- Price path (the key assumption): this is a scenario model, not a forecast and not a historical backtest. It assumes the price moves in equal steps from your start price to your end price across your buys. With 4 buys from $20,000 to $26,000, the buy prices are $20,000, $22,000, $24,000 and $26,000. Real prices zigzag — your real average depends on the prices you actually paid.
- Total invested = amount per buy × number of buys. Total fees = total invested × fee percent ÷ 100. Only the amount left after fees buys coins.
- Coins bought = the sum of every buy's coins. Average cost = total invested ÷ coins bought. Because cheaper buys buy more coins, this weighted average sits below the simple average of the buy prices whenever prices move.
- Final value = coins bought × end price. Profit or loss = final value − total invested, and ROI = profit ÷ total invested × 100.
- Lump-sum comparison: the same total amount invested once at the start price, paying the fee only once. In a steadily rising market the lump sum usually wins (your money is in sooner); in a falling market DCA usually loses less. The comparison shows both, so neither story is hidden.
Worked example (illustrative — a scenario, not a real plan or a prediction)
$100 a month, 4 months, $20,000 rising to $26,000, no fees. Buy prices: $20,000, $22,000, $24,000, $26,000. Coins: 100 ÷ 20,000 = 0.005; 100 ÷ 22,000 = 0.00454545; 100 ÷ 24,000 = 0.00416667; 100 ÷ 26,000 = 0.00384615. Total coins = 0.01755828. Total invested = $400. Average cost = 400 ÷ 0.01755828 = $22,781.28 — below the $23,000 simple average of the four prices, because the cheaper buys bought more coins. Final value = 0.01755828 × $26,000 = $456.52, a profit of $56.52 (14.13%). The same $400 as a lump sum at $20,000 would buy 0.02 coins, worth $520 — better here, because every month the price rose. DCA's value shows up when it does not.
The falling-market mirror. $100 a month for 3 months, $30,000 falling to $20,000, no fees. Buy prices $30,000, $25,000, $20,000 give 0.00333333 + 0.004 + 0.005 = 0.01233333 coins for $300, an average cost of $24,324.32, worth $246.67 at $20,000 — a $53.33 loss. A $300 lump sum at $30,000 would be worth only $200, a $100 loss. DCA did not prevent a loss; it softened it.
DCA vs lump sum — the honest trade-off
DCA is risk management, not return maximisation. When markets mostly rise, putting everything in at once wins on average — the money you held back was not riding the rise. Research on traditional markets (the well-known Vanguard finding) puts lump sum ahead roughly two-thirds of the time. DCA's real product is different: it protects you from your own worst timing — buying everything at a peak, panicking, and quitting. If you already have the full amount and strong nerves, lump sum is the mathematically favoured choice. If you are building the amount from income over time, or you know a crash would make you stop, DCA is the plan you will actually stick to — and a plan you stick to beats a perfect plan you abandon.
Watch the fees on small buys
Fees hurt DCA more than lump sums because you pay them on every buy. A 1% fee on a $100 monthly buy is $1 a month, $12 over a year — small. But a $1.50 flat fee on a $25 weekly buy is 6% on every single purchase, before any price movement. Enter your real fee percent above (a flat fee can be converted: flat fee ÷ buy amount × 100 = fee percent), and prefer percentage-based fees or free recurring buys for small amounts — or buy monthly instead of weekly.
FAQ
Does DCA guarantee a profit?
No. DCA does not assure a profit or protect against loss in a declining market. If the asset keeps falling and never recovers, DCA just means losing money more gradually. It reduces timing risk; it does not remove market risk.
Weekly or monthly — which is better?
The difference is small. Weekly buys give more averaging points; monthly buys usually mean lower total fees and match a payday. Pick the schedule you will not cancel — consistency matters far more than frequency.
Does this calculator use live crypto prices?
No. Everything runs in your browser and no prices are fetched. You type the start and end prices yourself — from your exchange, or as a scenario you want to test. That also means nothing here goes stale.
Is my average cost the same as my tax cost basis?
Not necessarily. This calculator's average cost is a planning number. Tax rules differ by country: the US generally tracks each buy as its own tax lot, while some countries allow an average-cost or pooled method. Keep your exchange's transaction history and check your local rules before filing — this tool is not tax advice.
Related from Bia Crypto
- Is DCA Into Bitcoin Still Worth It in 2026? The Honest Beginner's Guide — the companion guide: when DCA helps, when lump sum wins, and the fee trap on small buys.
- Crypto Profit Calculator — once you sell, work out the profit and ROI on that sale.
- Crypto Staking Rewards Calculator 2026 — what regular staking rewards add up to over time.
- Compound Interest Calculator — the same compounding idea for savings: how regular contributions grow over years.
- Is Coinbase Safe and Legit in 2026? — if you set up recurring buys, check the exchange's regulation and insurance first.
Sources
- SEC Investor.gov — Dollar Cost Averaging (the definition: equal portions, at regular intervals, regardless of market ups and downs)
- FINRA — The Pros and Cons of Dollar-Cost Averaging (benefits and downsides, including the lump-sum comparison)
- Kraken — Bitcoin Dollar-Cost Averaging (how recurring buys work on a major exchange)
Disclaimer: This tool is for education only. It is not financial or tax advice. Prices are scenarios you enter yourself, not forecasts — crypto is volatile and you can lose money, including everything you invest.
— Adrian Cole, Bia Crypto
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