Enter odds, market Spread, and stake to estimate the maximum loss (x) that keeps EV positive. Spread should be entered as a decimal (e.g., 0.02 for 2%).
The risk calculator tells you the largest loss a trade can take on the losing side while its expected value stays at zero or above. Enter the odds, the market spread and your stake, and it returns that maximum loss (x).
p = 1 ÷ odds − spread ÷ 2 (win probability at the mid-price)
q = 1 − p
n = (odds − 1) × stake (profit if the trade wins)
x = n × p ÷ qExpected value is p × n − q × x, so any loss up to x keeps the trade's EV at zero or above.
With a $100 stake at odds 2.10 and a 0.02 spread, p is 0.4662, the profit if the trade wins is $110.00, and the maximum loss is $96.07.
Holding to settlement risks the full $100 stake, which is more than $96.07. In this model, you would need to exit losing trades for less than $96.07 on average to keep a positive EV. The model assumes the trade wins with probability p and loses x otherwise; exits that happen before the result can change those chances.
The calculator takes half the spread off the implied probability, because buying at the ask costs half the spread above the mid-price. A wider spread lowers p and shrinks the loss you can afford.
Treat x as a budget for how much a losing trade may cost you, and compare it with where your stop-loss or exit rule would close the position.
Enter it as a decimal: 0.02 for a 2% spread.