Tool · Discipline · Three Modes

Bankroll
calculator.

The most important sum in sports betting: how much should you risk on this bet? Three modes (flat staking, a percentage of your bankroll and the Kelly Criterion) for bettors who want their bankroll to last.

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Optimal bet size

Choose your sizing methodology, then enter the inputs.

Enter your bankroll to see recommended bet size

The three modes, compared

Flat staking

Same Rand amount on every bet. Simple, predictable, low variance. Doesn't compound winning runs. Doesn't reduce stakes during losing runs. Best for new bettors who want to develop discipline before optimising. Standard recommendation: 1-2% of starting bankroll per bet.

Percentage staking

Fixed percentage of current bankroll. Self-adjusts: stakes grow with winning runs, shrink with losing runs. The most common professional approach. Standard recommendation: 1-3% per bet, 2% as default.

Kelly Criterion

Bet size based on your estimated edge, worked out as Kelly% = (b·p − q) ÷ b, where b = decimal odds − 1, p = your estimated chance of winning and q = 1 − p. In theory it gives the fastest long-term bankroll growth, but only if your edge estimate is accurate, which for most bettors it isn't. Use fractional Kelly (a quarter to a half of full Kelly) to allow for errors in your estimates.

Our recommendation

For most SA bettors, simple percentage staking at 2% per bet is the right answer. It's mathematically sound, psychologically manageable, and doesn't require you to estimate your edge precisely (which most bettors do badly). Kelly is for bettors who track every result over hundreds of bets and have empirical evidence of edge. Flat staking is for absolute beginners or for fixed-stake disciplines like accumulator betting.

Why position sizing matters more than picking winners

A bettor with a 55% win rate at even-money odds (2.00) has a clear edge. They'll be profitable over time. But if they bet 20% of bankroll on each pick, a normal 6-bet losing streak (which has roughly a 1-in-100 probability) blows up two-thirds of their bankroll. Variance kills bankrolls long before the underlying edge has time to manifest.

The same bettor at 2% a bet gets through a run of six losses easily, losing only about 12% of the bankroll, with plenty left to recover. Stake sizing isn't about squeezing out the maximum; it's about surviving.

* Bets until bust is a worst-case figure that assumes you lose every bet at the recommended size. Real losing runs are much shorter, but the number shows how aggressive staking eats into your margin for error.

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Common Questions

You asked.

Flat staking: the same rand amount on every bet (say R100). Simple and steady, but it doesn't adjust as your bankroll changes. Percentage staking: a fixed share of your current bankroll (say 2%), which adjusts automatically as the bankroll grows or shrinks. Kelly Criterion: stakes based on your estimated edge, bigger on stronger bets and smaller on marginal ones. It is the theoretical optimum, but it needs accurate edge estimates and produces big swings.

Money you can afford to lose entirely without affecting essentials. For sports betting at 1% to 2% a bet, you want a bankroll of at least 50 units, so if your usual bet is R100, your bankroll should be R5,000 or more. A smaller bankroll simply means smaller bets, which is fine. Never bet borrowed money, money meant for bills or money you will need back.

Full Kelly gives the fastest growth in theory, but it is hard to live with: a full-Kelly bettor has a 50% chance of seeing the bankroll halve at some point. Many professional bettors use quarter Kelly, which cuts the swings a lot while keeping much of the growth. For recreational bettors who don't track their edge precisely, quarter Kelly or simple percentage staking (1% to 2% a bet) is more practical than Kelly based on their own estimates.

Most bettors don't, even when they think they do. Your edge is your estimated probability minus the bookmaker's implied probability. If you think a team wins 55% of the time and the bookmaker offers 2.00 (50% implied), your edge is 5 percentage points. The catch is that your own estimate is usually too confident. Assume you are less right than you feel, and use fractional Kelly to allow for it.