The honest answer to “how big should my bankroll be” is that the size matters less than the fraction. We simulated 30,000 seasons to show what actually happens to a good bettor, and the drawdowns are larger than almost anybody expects.
Two different questions get muddled together here. What do people actually start with, and what should they bet per game. The first has real data behind it. The second has maths behind it, and the maths says something uncomfortable.
On this page
- What people actually deposit
- Where the one to two percent rule comes from
- Kelly, and why nobody bets it in full
- What a good bettor’s bad run looks like
- Unit size and going broke
- The hundred-bet illusion
- Where the money actually comes from
- Limits, and the one state that made them structural
- Common questions
What people actually deposit
The best data on this is a transaction-level academic study covering 230,171 households across roughly 4.9 million household-quarters from 2012 to 2023.
| Measure | Amount |
|---|---|
| Average deposit per quarter | $180 |
| High-intensity third, per quarter | $299 (1.7% of income) |
| Low-intensity third, per quarter | $1.39 |
| Bettors who deposit at least twice more | About 70% |
| Deposits after 12 quarters, relative to the first | About 8 times |
So the typical starting bankroll is roughly $60 a month, and the more revealing figure is the last one. Three years in, quarterly deposits are running around eight times the first deposit. Whatever people start with is not what they end up putting in.
A separate long-running study of 32,262 online bettors found a median of 15 bets in total, a median stake of about six euros and a median net loss of 25 euros. The median online sports bettor is a small-stakes, short-duration customer who is not really doing bankroll management at all.
Studies of monthly betting activity put US live bettors at $1,583.90 of monthly spend against $846.20 for pregame bettors. Those are handle figures, not deposits. Handle recycles winnings, so someone depositing $60 a month can easily put $800 through the window. The gap between the two is what churn looks like.
On minimum deposits, the split is worth knowing. Most regulated US books take $5 or $10 to open. Offshore books want considerably more, with reported minimums around $10 to $20 in crypto but $25 to $50 by card, and higher at some. If you are testing an offshore book, expect the entry cost to be several times what a regulated app asks for.
Where the one to two percent rule comes from
Everyone repeats 1 to 3 percent per bet, and nobody explains why. We looked for an origin and could not find one, so here is the reason it survives, which is better than an origin.
At -110 pricing, the Kelly criterion tells you what fraction of a bankroll to risk given an edge. Run it and the answer for a 55 percent bettor is 5.5 percent of bankroll per bet. For a 53 percent bettor it is 1.3 percent. For a break-even bettor it is zero.
| True win rate | Full Kelly | Half Kelly | Quarter Kelly |
|---|---|---|---|
| 52.38% (break-even) | 0% | 0% | 0% |
| 53% | 1.30% | 0.65% | 0.33% |
| 55% | 5.50% | 2.75% | 1.38% |
| 57% | 9.70% | 4.85% | 2.42% |
One to two percent is roughly the correct full-Kelly stake for someone winning 53 to 54 percent, which is already a good bettor. Applied at quarter Kelly, a genuine 55 percent bettor should be at 1.38 percent. So the conventional advice is not conservative for most people. For anyone whose true edge is smaller than they think, it is overbetting.
The asymmetry is why practitioners err low. Underbetting when you have an edge costs you growth. Overbetting when you have an edge, or having no edge at all, costs you the bankroll.
Kelly, and why nobody bets it in full
The formula comes from a 1956 Bell System Technical Journal paper by J. L. Kelly Jr. on information rate. It maximises long-run growth, and under continuous rebalancing with a correctly known edge, a Kelly bettor never goes broke, because the stake shrinks as the bankroll does.
Two things break that in practice.
You do not know your edge. Kelly assumes you know your win probability. Overestimate it by a few points and you are overbetting by a multiple, not a margin. This is the main reason serious bettors use half or quarter Kelly.
The variance at full Kelly is brutal. The academic work here is by MacLean, Thorp and Ziemba. For a two percent advantage, their figures are the ones to remember: at full Kelly the probability of doubling your bankroll before halving it is 0.67. At half Kelly it rises to 0.89, and you give up 25 percent of the growth rate to get there. Most people will take that trade every time.
Note also the general relation that betting twice the Kelly stake produces zero long-term growth. Not slower growth. Zero. There is a stake size at which a genuine edge stops being worth anything, and it is closer than people think.
What a good bettor’s bad run looks like
We could not find published work on this, so we ran it ourselves. Thirty thousand simulated runs of 1,000 bets each, flat one unit per bet at -110, at a genuine 55 percent win rate. That bettor has a five percent return on turnover, which is a career-grade edge.
| Percentile | Worst drawdown |
|---|---|
| Median run | 21.0 units |
| 75th percentile | 26.6 units |
| 90th percentile | 33.7 units |
| 95th percentile | 39.0 units |
| 99th percentile | 50.7 units |
| Worst of 30,000 runs | 99.2 units |
The median outcome for a bettor with a real, strong edge is a drawdown of 21 units at some point in a thousand bets. One run in ten sees 34 units. One in a hundred sees 51.
Losing streaks follow the same shape. Over 1,000 bets at 55 percent, the median longest losing run is eight straight. One run in ten hits ten straight, one in a hundred hits 13, and the worst we saw across 30,000 runs was 22 consecutive losses.
If your unit is three percent of bankroll, a median drawdown of 21 units is 63 percent of everything you have. If your unit is one percent, the same drawdown is 21 percent and survivable. The drawdowns above are what a good bettor should plan for, not a worst case. Anyone telling you a real edge means smooth results has not run the numbers.
Unit size and going broke
Same simulation, now asking how often the bankroll is gone entirely within 1,000 bets at a flat stake.
| Unit size | 55% bettor | Break-even bettor |
|---|---|---|
| 1% of bankroll | 0.00% | 0.07% |
| 2% | 0.34% | 10.66% |
| 3% | 2.35% | 28.17% |
| 5% | 11.32% | 52.50% |
| 10% | 35.17% | 75.94% |
Read the right-hand column. A bettor with no edge at all, betting three percent a game, is gone within a thousand bets more than a quarter of the time. At five percent it is a coin flip. And a break-even bettor is doing well by the standards of the actual population, because most bettors are worse than break-even once the hold is applied.
Read the left-hand column too. Even with a career-grade edge, five percent units bust you eleven times in a hundred. The edge does not protect you from your own sizing.
The hundred-bet illusion
Here is the number that explains most of the confusion people have about their own results.
Take a 55 percent bettor at $100 flat. Expected profit over 100 bets is $500. The standard deviation over those same 100 bets is $950, almost twice the expected profit.
| Bets | 53% bettor down | 55% bettor down | 57% bettor down |
|---|---|---|---|
| 100 | 45.9% | 31.3% | 17.8% |
| 250 | 40.0% | 19.4% | 6.3% |
| 500 | 37.3% | 11.2% | 1.7% |
| 1,000 | 34.1% | 4.9% | 0.1% |
A genuine 55 percent bettor is down after 100 bets almost a third of the time. A 53 percent bettor, who is still a winning bettor, is down after a full thousand bets more than a third of the time.
Two conclusions follow, and they point in opposite directions. Your losing month tells you nothing. And neither does anybody else’s winning one, which is the point we make at length in how to tell a real record from a fake one.
Where the money actually comes from
You will see it claimed that 95 or 97 percent of bettors lose. We went looking for the source of that figure and there is not one. It appears only in unattributed secondary content, so we are not going to repeat it.
What is real is better anyway.
The aggregate hold on US sports betting was 6.9 percent in 2019 and 10.2 percent in 2025, rising roughly a point a year as parlay mix has grown. Bettors as a group lost ten cents of every dollar staked last year. That is the arithmetic floor and it does not require anyone to guess at percentages.
On distribution, a study of 140,000 online accounts across seven operators found that the five percent of accounts with the largest losses generated 70 percent of gross gambling yield. For sports betting specifically, the top ten percent of customers by stake generated 79 percent of betting revenue. In the tail, 0.7 percent of accounts lost £5,000 or more in a year and 0.1 percent lost over £20,000.
The industry does not run on the median customer. It runs on a small group at the top of the loss distribution. Bankroll rules are not really about optimising growth for most people. They are about not becoming part of that five percent.
Separately, the best available research on downstream harm links online sports betting access to a roughly ten percent increase in bankruptcy filings and a small average drop in credit scores, with the authors noting that because the study cannot identify individual bettors, the per-bettor effects are likely five to ten times larger than the population averages.
Limits, and the one state that made them structural
Every major regulated book offers deposit limits, loss limits, time limits, cool-off periods and self-exclusion. All of them are opt-in, which means almost nobody uses them.
Historic operator data makes the point. One book applied default limits of 1,000 euros per day and 5,000 per month, and only 0.3 percent of 47,000 customers ever hit them. Default limits bind almost nobody, but the people they bind are precisely the tail.
Two 2026 developments are worth knowing:
- Colorado’s Sports Betting Protections Act, effective 12 August 2026, caps customers at six separate deposits per 24-hour gaming day. That is a genuine structural limit rather than a voluntary tool, and it is the first of its kind in the US. The same act bans credit card deposits outright and bars sportsbooks from limiting bet sizes purely because a customer is winning.
- Credit card bans are now in force in around nine states, and one major operator dropped credit card deposits voluntarily in 2025.
The contrast worth noting is the UK, where operators must run financial vulnerability checks at 150 pounds of net deposits in a rolling 30 days, using public data only. Roughly seven percent of active accounts were checked in the first months of the higher 500 pound threshold. Nothing comparable exists in the US.
If you take one practical action from this page, set a deposit limit before you need one. It costs nothing, it takes a minute, and the entire body of evidence above says the people who benefit most are the ones who would never think to.
How big should my sports betting bankroll be?
Big enough that your normal bet is one to two percent of it, and no bigger than you are willing to lose entirely. The size in dollars matters far less than the fraction. Our simulations show a genuine 55 percent bettor betting one percent per game essentially never busts within a thousand bets, while the same bettor at five percent per game busts 11.3 percent of the time. A break-even bettor at five percent units busts more than half the time.
What do most people actually start with?
Less than you would guess. Transaction-level data from 230,171 US households puts average deposits at $180 per quarter among households that bet at all, roughly $60 a month, with the highest-intensity third at $299 a quarter. The more revealing figure is that about 70 percent of bettors go on to deposit at least twice more, and after twelve quarters deposits run around eight times the initial one. Most regulated US books take $5 or $10 to open an account, while offshore books typically want more.
What percentage of my bankroll should I bet per game?
One to two percent for almost everyone. The reason is Kelly. At -110 pricing, full Kelly for a genuine 55 percent bettor is 5.5 percent of bankroll, and practitioners bet a quarter to a half of that, which lands at 1.4 to 2.8 percent. For a 53 percent bettor, full Kelly is only 1.3 percent. So one to two percent is roughly correct full-Kelly sizing for a good bettor, which means it is overbetting for anyone whose edge is smaller than they believe.
How bad a losing streak should I expect if I am actually winning?
Worse than most people plan for. We simulated 30,000 runs of 1,000 bets at a genuine 55 percent win rate with flat one-unit staking. The median run had a worst peak-to-trough drawdown of 21 units. One run in ten reached 33.7 units, one in a hundred reached 50.7, and the worst run of 30,000 hit 99.2. On losing streaks, the median longest run was eight straight losses, one in ten hit ten straight and one in a hundred hit thirteen.
Why am I down when I think I have an edge?
Because a hundred bets tells you almost nothing. A genuine 55 percent bettor at $100 a bet expects $500 profit over 100 bets, but the standard deviation over those same bets is $950. Our simulations put that bettor down after 100 bets 31.3 percent of the time, and a 53 percent bettor, who is still a winner, is down after a full thousand bets 34.1 percent of the time. Your losing month is not evidence of anything.
Is it true that 95 percent of bettors lose money?
We could not find a primary source for that figure and would not publish it. What is documented is better. The aggregate hold on US sports betting rose from 6.9 percent in 2019 to 10.2 percent in 2025, so bettors as a group lost about ten cents of every dollar staked. And a study of 140,000 online accounts found the five percent of accounts with the largest losses generated 70 percent of gross gambling yield, with the top ten percent of sports betting customers by stake generating 79 percent of betting revenue.
Should I set a deposit limit?
Yes, and before you feel you need one. Every major regulated book offers deposit, loss and time limits plus cool-off periods and self-exclusion, and all of them are opt-in, which is why almost nobody uses them. One operator’s historic data showed that with default limits of 1,000 euros a day, only 0.3 percent of 47,000 customers ever hit them. Colorado went further with an act effective 12 August 2026 capping customers at six deposits per 24-hour gaming day, the first structural limit of its kind in the US.
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