Betting money and bet size
How much to bet, so a bad run doesn't wipe you out.
3 min readChecked on Oct 31, 2026
Your betting money (also called a bankroll) is the money you set aside for betting, and only that money. Pick an amount you can lose without it changing your life. Not rent, not savings, not borrowed money.
Every bet (also called a stake) is then a share of that number. So a bad run makes your bets smaller instead of wiping you out.
Bet size matters as much as value
Good bets still lose in streaks. Four coin-flip bets in a row all lose about 1 time in 16. Say each bet is 25% of your betting money. Those four losses leave you with 32% of it.
At 2% a bet, the same four losses leave 92%. You are still in the game.
The formula
f = (b x p - (1 - p)) / bb = decimal odds - 1p = your fair chance of winningf = the share of your betting money to betThe formula gives the amount that grows your money fastest over the long run, if your chance p is right. When the bet has no value, f comes out at zero or below. Then don't bet.
50% at 2.10 with $1,000 of betting money
- b = 2.10 - 1 = 1.10, and p = 0.50.
- f = (1.10 x 0.50 - 0.50) / 1.10 = 4.55% of your betting money.
- The full amount: $45.45. Bold: $22.73. Normal: $11.36. Careful: $4.55.
Why WynFynd bets a share of it
The full amount assumes you know the true chance exactly. You don't. A fair chance worked out from prices is only an estimate. When it is a little too high, the full amount bets too much. It also swings hard.
So each Bet size bets a share of the full amount: Careful a tenth, Normal a quarter and Bold half. You give up a little growth for much smaller swings. Normal is the default.
| Bet size | Amount | Ever halves |
|---|---|---|
| Full amount (for reference) | $45.45 | 1 in 2 |
| Bold | $22.73 | 1 in 8 |
| Normal (default) | $11.36 | 1 in 128 |
| Careful | $4.55 | 1 in 524,288 |
The last column is a standard result from the theory, for someone whose chances are exactly right. Real bettors whose chances are a little off do worse. That is one more reason to bet a share.
Pick Careful, Normal, Bold or your own size in Alerts.
The 20% cap and other limits
The formula can ask for a big amount when a bet looks very good. A very good-looking price is often a mistake, in the price or in the fair chance.
So WynFynd caps any one bet at 20% of your betting money, unless you set your own cap. In Alerts you can also set a daily limit, a weekly limit and a daily loss limit. Once you hit your daily loss limit, alerts stop until the next day.
Both-sides bets and your betting money
Both-sides bets don't use the formula. Every side is split so the result is the same whoever wins. How big one can be depends only on how much you can put at each site.
After one pays out, the money sits at the site that won. Over time it piles up at some sites and runs low at others. WynFynd's Money screen shows how much you have at each site.
- Keep your betting money apart from everyday money, so you always know how much you really have.
- Update your betting money in WynFynd when it changes a lot, so amounts stay a sensible size.
- After a losing run, let your bets shrink with your money. Never raise them to win it back (see tilt).