Observation Deck / DCA Analysis

₿itcoin DCA Calculator

Dollar-cost averaging β€” a fixed dollar amount, bought on a fixed schedule β€” replayed against real Bitcoin closing prices. A backtest, not a forecast.
Set a start date, how often you buy and how much — every figure updates as you go.

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How this works

The simulation

  • “Monthly” means every 30 days, not the same date each calendar month β€” about 12.2 buys a year, and the date drifts earlier over time. Weekly is 7 days, bi-weekly is 14.
  • Each purchase fills at that UTC day’s closing price β€” the most recent close on or before the date, never a later one. Intraday highs and lows are ignored.
  • No fees, spreads, or taxes. A platform charging ~1% a buy would leave you ~1% less Bitcoin every time, so every figure here is an optimistic upper bound. Nothing is ever sold β€” profit is unrealised.
  • Buying continues through today, so an earlier start date also means more total dollars invested. Compare runs on ROI, not on profit.

Reading the results

  • Average Cost per BTC lands below the average price you actually paid β€” a fixed dollar amount buys more Bitcoin when the price is low. That gap is dollar-cost averaging doing its job.
  • Return on Investment is the total across the whole duration. Annualised Return is the money-weighted rate (XIRR) β€” it accounts for when each contribution actually went in, so it is the figure to compare runs of different lengths on. Don’t divide ROI by the number of years.
  • Portfolio Value prices your whole stack at the most recent daily close. In the history table, Value on Date prices it at that row’s date instead β€” which is why the last row and the summary differ.

Your plan

Frequency
Portfolio value
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The averaging effect

Your average cost per BTC —
Average price on your purchase dates —

Did your start date matter? Annualised return for every start month, by how long you held

Each square is a plan of its own: start buying that month on your current schedule, hold for the period on the left, stop. The colour is that plan’s money-weighted annualised return — the same figure the tiles report. Rates don’t depend on how much you buy, so changing the amount moves nothing here; changing the frequency does.

 

    One historical window, not a forecast. A short window mostly measures where the price happened to be when you started — the case for DCA rests on horizons measured in years. Drag the start date to watch the average cost move. Fees, spreads and taxes are not included.

    Purchase history
    Click a column to sort. Value on Date prices the stack at that row’s close.
    # Date BTC Price BTC Bought Total BTC Total Invested Value on Date Profit / Loss