See the whole distribution, not one number.
Most calculators hand you a single confident number. compoundcoast runs your inputs across history and shows the range — a 5th-percentile downside, a median, and a 95th-percentile upside — net of fees and tax, with the source and as-of date on every figure.
The three-stage journey
Accumulate the pile, reach your number, then draw it down without running out. Each stage groups the calculators that answer its questions.
Signature: the rolling-window reality engine
illustrativeOne backtest engine drives the whole site. It replays every historical start month — total return with dividends reinvested, idle cash credited at T-bill rates, taxes and expense ratios applied, then adjusted for inflation — and reports a win-rate and a full percentile band instead of a single point. The bar below is an illustrative shape of a DCA-vs-lump-sum outcome spread, not your result:
Illustrative distribution of an ending-balance difference. The coral marker is the worst historical start date; the mint marker is the most favorable. Real results depend on your inputs and the data's as-of dates.
We show the math
Ranges, never a point
Every headline is a p5 / median / p95 band. A single number hides the downside that matters most for a retirement or a lump-sum decision.
Sources on every figure
Each input carries its source and as-of date — Shiller, the French Data Library, IRS, SSA, BLS, HHS. Stale data breaks the build rather than misinform you.
Net of fees and tax
Expense ratios, advice fees, and the current-year tax engine are applied before the headline, so a 7% gross return is not quietly presented as spendable.
Start reading
- Methodology
The four non-negotiable contracts behind every result.
- Guides
Plain-language explainers on the ideas the calculators use.
- All calculators
The full index across all three stages.