Portfolio Allocation Calculator

One pot split four ways, with each share compounding at its own rate. Contributions are divided by your target split rather than dropped into whichever sleeve is largest, and withdrawals come out of all four in proportion to what each is worth at the time, so drawing money down does not quietly change your allocation. If the sliders do not add up to 100%, nothing is left uninvested — the split is scaled proportionally, and the tab tells you so.

The blended return shown in the results is a weighted average of the four rates you set, and it is the least useful number on the page. It cannot tell you anything you did not already put in. Everything worth knowing here is about what happens to that average on the way.

Rebalancing is the real subject. Once a year, the tab sells whatever grew and buys whatever lagged, back to your target. That usually ends up slightly lower than leaving it alone, because in a long stock run you are trimming the winner every year — this is the cost, and the tab shows it rather than presenting rebalancing as free. What you get back is a narrower range of outcomes. Switch rebalancing off, and the tab reports what your mix has drifted into by the final year, which is often a far more aggressive portfolio than the one you chose, arrived at without ever deciding.

The blend is tested two ways, and neither is flattering by design. The thousand-run fan reports where this mix lands in the worst tenth of futures against 100% stocks in its worst tenth — and it will sometimes report that the blend’s floor is lower, meaning the return you gave up cost more than the volatility you shed. The historical overlay runs your allocation through real years starting from a date you choose, against all-stocks over the same period. Start it in 2000 or 1972, and the blend usually looks wise; start it in a calm decade, and it looks expensive. Both are true, which is the point of being able to move the date.

What this does not do is model how the four move together. In the simulated fan, each is randomized independently, so no correlation exists at all — and whether that flatters the blend or undersells it depends on the decade you imagine. The historical overlay is the honest test because real years reflect whatever correlation occurred. Beyond that: no fund fees on any sleeve, no trading costs, and no tax on rebalancing, which in a taxable account means selling winners and realizing gains every single year. Real estate is left out on purpose — a mortgage makes it a leveraged position that a percentage slider cannot honestly represent. It has its own tab.