How it works
Lump-sum-versus-DCA arguments usually collapse into one deterministic spreadsheet; this calculator refuses that simplicity and prices three labeled paths instead. The steady case drifts upward at your assumed return, rewarding immediate deployment because money compounds longest when invested earliest. The bear case drops hard during the first third of the deployment window — DCA tranches buy the dip at successively better prices, finishing ahead of a lump sum that absorbed the full fall at once. The bull case pops early, handing lump-sum the maximum head start and leaving DCA perpetually chasing. Run the defaults — $60,000 over twelve months at an 8% drift with a −25%/+12% opening shock pair — and lump sum wins two of three scenarios, consistent with the historical finding that immediate deployment finishes ahead roughly two-thirds of the time across past market periods. That majority statistic is context, not counsel: the losing third is exactly the crash scenario where DCA's psychological insurance pays most, and the 'right' answer depends on which regret you'd rather own — missing upside or catching a drawdown at full size. The schedule table shows the uninvested remainder month by month, which should sit in a high-yield account either way.
Formula
Lump = amount × index(end) | DCA = Σ (amount/months ÷ index(m)) × index(end), m = 1…window
Tips
- Park uninvested DCA tranches in a high-yield account — idle cash should still earn.
- Shorter windows favor lump sum; twelve months is the common compromise length.
- Choose by regret tolerance: which miss would you replay mentally for years?
- Automate the tranche dates before starting; manual DCA quietly becomes market timing.
- Re-run with a −40% bear case occasionally — deep-scenario results change decisions.
Frequently asked questions
- Is it better to invest a lump sum all at once?
- Historically, yes about two-thirds of the time — markets rise more often than they fall, so immediate deployment captures more up-years. This tool's steady and bull cases reproduce that edge in dollars; the remaining third is the crash scenario where spreading entries wins instead.
- When does dollar-cost averaging beat lump sum?
- When prices fall materially during the deployment window: later tranches buy cheaper units, ending ahead despite less time in the market. Here a −25% early drop hands DCA roughly a four-figure advantage on $60,000 — the insurance premium logic running in reverse.
- How long should I spread a DCA program?
- Six to twelve months covers most windfall situations. Longer windows increase the chance of capturing a dip but leave more cash idle against the steady-case gap, which grows with both the return assumption and the square of the delay. Twelve months remains the practical default compromise.
- Does DCA reduce risk or just returns?
- Both, asymmetrically. It reduces sequence-of-entry risk — the specific danger of deploying everything immediately before a decline — while statistically sacrificing expected return. Whether that trade suits you depends on horizon, cash-flow stability and how you'd emotionally process a fast drawdown at full position size.
- What should I do with cash between DCA tranches?
- High-yield savings, money market funds or short T-bills — liquid, principal-stable, currently yielding meaningfully. Every basis point earned narrows the steady-case gap against lump sum slightly, and parking it in checking or, worse, spending it is the classic DCA failure mode.