Betting variance simulator

Variance is the randomness that makes your actual results drift away from your expected results, especially over short samples. With a genuine 3% edge it is completely normal to lose money over a month, and not rare to be behind after several hundred bets. The simulator makes that visible before it happens to you, which is the difference between quitting a working strategy and sitting through the dip.

Your edge and average odds set a win probability: with a 3% edge at 1.90 the bet wins 54.2% of the time (break-even is 52.6%). Each run then plays that bet the chosen number of times with your staking plan, and thousands of runs are combined into the bands, the histogram and the risk numbers. The median line is what a typical bettor sees; the mean is the expected value, which sits higher because a few runs go very well.

Risk of ruin is the share of runs that lost the whole bankroll. Even a profitable strategy can go bust if stakes are too large for the bankroll. Max drawdown is the biggest fall from a peak within a run; the typical value tells you what to expect, the bad-case value tells you what to survive. Both shrink quickly as the stake percentage comes down, which is the whole argument for the fractional Kelly stake sizes.

Flat staking bets a fixed amount every time, set as a percentage of the starting bankroll. Simple and predictable, but it never adapts: after a drawdown the stake is a larger share of what is left.

Kelly staking re-sizes each bet from the current bankroll and your edge, so stakes fall in a downswing and rise in an upswing. That is why Kelly runs almost never go bust while flat runs can, and why full Kelly still produces brutal drawdowns. Switch between the methods above with the same edge to compare the shape of the bands.