Most people decide what they would have invested by looking at the chart and picking a date that makes the result look good. Real DCA does not work that way. You commit to a fixed amount on a fixed schedule and you keep going through every drawdown along the way.
This calculator replays that decision honestly. For every contribution date in the range you set, it buys the asset at that day's adjusted close, accumulates the shares, and tracks the portfolio value over time. No cherry-picking, no rebalancing tricks. Just the math you would have lived through.