Portfolio Backtest
Test any mix of ETFs, index funds, mutual funds and institutional asset classes against their real history. No account, no lookback cap, no limit on how many times you run it.
Holdings
100.0% of 100%How far back it goes
A backtest reaches as far as its shortest holding, which is usually the constraint people trip over. One fund launched in 2015 caps the whole portfolio at 2015 however old everything else is.
Older mutual funds often solve it. VFINX has tracked the S&P 500 since February 1990 and VBMFX the US aggregate bond market for as long, so a two-fund portfolio built from those reaches back thirty-six years — through 2000, 2008 and 2020 — where the ETF equivalents would start in the 2000s.
The 27 asset classes use institutional index data and mostly begin in the 2000s, with US large cap reaching 1993. They are the better choice when you want exposure without picking a specific fund.
What a backtest can’t tell you
Every backtest describes one sequence of events that happened once. The period you test largely determines the answer you get: run 2009 to 2021 and equities look unbeatable, run 2000 to 2010 and they look broken. Neither is a forecast.
It is also silently biased toward whatever survived. The funds available to test today are the ones that lasted, and the strategies that look best in hindsight are frequently the ones that were most uncomfortable to hold.
That is why the same portfolio is worth running forwards as well — against published capital market assumptions rather than the past, and through a Monte Carlo simulation that shows the range of outcomes rather than the single one history dealt.