The method
How it works
No secret model and no hunches. Parity Odds does what careful bettors do by hand, on every price, every few minutes.
- 1
Collect every price
Several times a day, and just before games start, we pull the odds from the major US sportsbooks and from sharp books in one sweep.
- 2
Remove the vig
Each sharp book's two prices on a bet add up to more than 100%. We scale them back to 100% and average across sharp books to get the fair chance.
- 3
Compare your books
Every price at the books you use is checked against that fair chance. When a book pays more than fair, the difference is the edge.
- 4
Size the stake
Bets that clear your minimum edge get a stake from your bankroll using fractional Kelly with a cap, so no single bet can hurt much.
- 5
Grade on the close
When you log a pick, we save the price. Just before the game, we record the fair closing price and grade your pick on the difference.
A worked example
A sharp book prices a game at -150 for the home team and +130 for the away team. Those imply 60.0% and 43.5%, 103.5% in total. Scaled back to 100%, the fair chances are 58.0% and 42.0%.
The fair price for the away team is about +138. If your book offers +150 on them, the bet is worth 42.0% x 2.50 = 1.05 per dollar: a 5% edge. At +130 it would be worth 0.97 per dollar, a loss on average, even though it’s the same team.
With a $1,000 bankroll and quarter Kelly, that 5% edge at +150 stakes about $8.40 (full Kelly would be 3.4% of the bankroll; a quarter of that is 0.84%).
Try it yourself with the de-vig calculator and the Kelly calculator.
The math, line by line
- Sharp prices
- -150 / +130
- Implied, with vig
- 60.0% + 43.5% = 103.5%
- Fair chance, away
- 43.5 ÷ 103.5 = 42.0%
- Fair price, away
- +138
- Your book pays
- +150 (2.50)
- Value per $1
- 0.420 × 2.50 = 1.05
What it can’t do
- Edges big enough to bet are uncommon. On many days the board shows none, and it says so.
- The fair price is an estimate. Sharp books are very good, not perfect, and they don’t post every market; where they don’t, we use the consensus of many books and label it.
- Prices move. The board shows how old each scan is, and a price can be gone by the time you open your book.
- Sportsbooks may limit accounts that consistently beat the closing line. That’s their policy, and it’s worth knowing before you start.
- It never places a bet. Every decision is yours. See responsible gambling.