Monte Carlo Retirement Calculator

A steady return is an average no portfolio ever actually delivers, and taking a fixed withdrawal from a balance that moves makes the order of the returns matter. This runs your plan through a thousand to five thousand simulated lifetimes with returns drawn from a lognormal fitted to the average and the volatility you enter, then reports the tenth, twenty fifth, fiftieth, seventy fifth and ninetieth percentile of the ending balance, and how early the failures failed. The random numbers are seeded from the inputs themselves, so the same figures always produce the same answer rather than a fresh guess on every reload. Set volatility to zero and it collapses to the plain arithmetic a fixed rate calculator gives.

Taken at the start of the year, then raised by inflation every year after.
Nominal, before inflation, as an arithmetic average of the yearly returns.
Roughly 15 for a global stock portfolio, 9 or 10 for a sixty forty mix, 5 for something conservative. Enter 0 to turn the randomness off and get the plain arithmetic answer.
Applied to the withdrawal every year. It is held steady rather than randomised, so the spread you see below is return risk alone.
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