This betting variance calculator shows how much luck can swing your results. It simulates 40 bettors who all place the same bets, at the same odds, with the same edge. Then it charts how differently they end up.
It is a reality check. Even with a real edge, some of those bettors finish behind, and long losing runs are normal.
Variance simulator
The short version
- Each run is random, so the 40 results change every time.
- Expected profit = number of bets × stake × edge.
- The bigger the odds, the wider the swings.
How to use the betting variance calculator
Enter the number of bets, the decimal odds, your edge as a % and your stake. Then the calculator plays out 40 bettors.
It shows a chart of every path, plus the expected profit, the middle result, the worst and the best. It also counts how many ended behind and gives the typical longest losing streak.
Worked example
Worked example
Say you place 500 bets of £10 at odds of 2.00, with a 3% edge. That means each bet wins 51.5% of the time, because 1.03 ÷ 2.00 = 0.515.
The expected profit is 500 × £10 × 3% = £150. However, the standard deviation over 500 bets is about £224, so results spread widely.
As a result, about 1 in 4 bettors should end behind, which is roughly 10 of the 40. A longest losing run of about 8 bets in a row is typical. Your run will differ, because each simulation is random.
What the result means
A few hundred bets is not enough to prove an edge, or to rule one out. So a bad month does not mean your method is broken, and a good month does not prove it works. Our guide to betting variance explains how many bets you really need.
Also, the betting variance calculator assumes your edge is real. If it is not, the middle result moves below zero. Most bettors lose over time, so treat any edge as unproven.
Why the betting variance calculator matters for staking
Swings like these are why stakes should stay small next to your bankroll. For example, the Kelly calculator sizes stakes to your edge, and the betting ROI calculator shows how your own record compares. For the maths of win counts, see the binomial distribution.
Related guides and calculators
18+ only. Betting should be fun, and every bet can lose. Set a budget you can afford to lose and stick to it. For free, confidential support, visit BeGambleAware.org or call the National Gambling Helpline on 0808 8020 133.