The EV calculator answers: at this price, versus the fair odds, is the bet +EV — and by how much?
Reading the number
A positive EV% means you profit on average over many bets. Tiny edges (under ~1–2%) can be noise or stale data; treat them with caution.
Sizing the bet
Once you know your edge, Kelly sizes the stake as a fraction of your bankroll — bigger edge, bigger stake, but never your whole bank. Most bettors use quarter- or half-Kelly to smooth variance. Promo conversions are near-guaranteed so they don't need Kelly; value bets do.