Variance Simulator
See how far results swing over a session before the edge shows.
median · 25–75% band · 5–95% band · expected value (dashed)
- Sessions in profit
- 79.8%
- Median result
- +20.0u
- Expected value
- +20.0u
- 5–95% range
- -18u to +56u
- Worst session
- -62u
- Typical max drawdown
- -19u (worst -36u)
With a 52.0% edge over 500 bets, results still land below zero 20% of the time. The gap between the band edges is variance — that is what a bankroll has to absorb.
A positive edge only pays out over the long run. Across a single session — a few hundred bets — luck dominates, and even a solid advantage can sit well underwater. This simulator runs many sessions with the same edge so you can see the whole range of results, not just the average.
Watch the spread between the best and worst runs. That gap is your variance, and it is what a bankroll has to absorb. The bigger it is relative to your stake, the more cushion you need before the edge reliably lifts you into profit.
FAQ
- Why do I lose over a session even with an edge?
- Because variance is larger than the edge over short samples. A 2% edge earns roughly 2 units per 100 bets on average, but the standard deviation over 100 bets can be 10 units or more — so losing stretches are normal and expected.
- How many bets until the edge shows?
- It depends on the edge and the odds, but as a rough guide you often need thousands of bets before results consistently track expectation. Smaller edges take far longer.
- How does this relate to bankroll size?
- The wider the outcome spread, the larger the bankroll you need to survive a bad run without going broke. Pair this with the bankroll and Kelly tools to size stakes against that risk.