The formula
For a bet that risks R to win W, the break-even win rate is R ÷ (R + W). At standard −110 pricing that's 110 ÷ 210 = 52.38%. Win 52% of −110 bets over the long run and you still lose money.
Common prices
- −105: about 51.2% to break even
- −110: about 52.4%
- −115: about 53.5%
- −120: about 54.5%
- +100 (even money): 50%
Where the margin comes from
On a two-way market priced −110 on both sides, the implied probabilities add up to about 104.8%. The extra 4.8 percentage points is the book's built-in margin (the overround, which is where the vig comes from). Removing it gives a “no-vig” price, a fair-odds estimate the odds converter can calculate.
What it means for you
- Every few cents of price matters, which is why line shopping pays.
- A small edge over the break-even rate is a real edge, but only over a large number of bets.
- Judging results by win rate alone is misleading at different prices: track units instead (units and bankroll).