## EV Alone Is Not Enough
Knowing a bet is +5% EV tells you it is worth betting. It does not tell you how much to bet. This is where EV and staking theory intersect.
## The Kelly Connection
The Kelly Criterion derives the optimal stake size from EV:
Kelly % = (P × B − Q) / B
Where P = win probability, Q = 1−P, B = net odds (decimal − 1)
This formula maximises the geometric growth of your bankroll. At the same EV, higher-odds bets receive smaller Kelly fractions because their variance is higher.
## Worked Example
EV +5% on a 3.00 bet (P = 0.40, B = 2.00, Q = 0.60):
Kelly % = (0.40 × 2.00 − 0.60) / 2.00 = (0.80 − 0.60) / 2.00 = 0.10 = 10% of bankroll
EV +5% on a 1.80 bet (P = 0.60, B = 0.80, Q = 0.40):
Kelly % = (0.60 × 0.80 − 0.40) / 0.80 = (0.48 − 0.40) / 0.80 = 0.10 = 10% of bankroll
Same EV, same Kelly fraction — because EV% and Kelly fraction are directly proportional given the same odds structure.
## Practical EV-Driven Staking
Most bettors use fractional Kelly (25–50% of full Kelly) to reduce variance while still scaling stakes with EV:
Stake = (EV% / B) × bankroll × Kelly fraction
The key discipline: bet more on higher EV, less on lower EV — not more on higher confidence or longer price.
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