THE MATHS, MADE CLEAR
How it works
Expected value is a probability-weighted average, not the return on the next bet. For a binary win/loss bet, the expected profit is p × stake × (odds − 1) minus (1 − p) × stake. The estimate is only as sound as the probability entered. Small estimation errors can turn an apparent positive edge into a negative one.
EV per unit = (win probability × decimal odds) − 1
A worked example
At 2.10 odds with an estimated 52% chance of winning, EV per unit is (0.52 × 2.10) − 1 = +0.092. That is +9.2%, or +9.20 units expected profit on a 100-unit stake. Break-even probability is 47.62%.
Understand the assumptions.
These are educational calculations, not predictions or recommendations. Display amounts are rounded to two decimal places; calculations retain internal precision.