Free tool
Expected Value Calculator
Whether a price is worth taking. Give it what you think the bet is really worth and what a book is paying, and it returns the edge — as a percentage and in dollars per $100 — with both implied probabilities, so you can see exactly where the number comes from.
Enter the price you're offered and this fills in. Without a fair price there is no edge to measure — we won't invent one.
How it works
With p the probability implied by the fair price and payout the decimal odds you're offered, EV = p × payout − 1. Positive means the price pays more than the outcome is worth; negative means it pays less, and no amount of confidence changes that.
This is the same computation the board runs on every game, so a number here and a number there always agree. EV says whether to bet; the Kelly calculator says how much.