Synthetic Hold Calculator
Enter each book's price on both sides of the same market. The calculator finds the best price on each side, combines them into one synthetic market and shows what the whole market charges compared with any single book. New to the idea? Read Synthetic Hold: Price the Market, Not the Book.
Every row must be priced at the same line. An over at 41.5 and an under at 42 are different bets, so remove books quoting a different number. Two-way markets only (totals, spreads, moneylines without a draw).
| Book | Over | Under | Hold | Fair Over | Remove |
|---|
Best price on each side is outlined in green. “Fair” removes that book's own margin from its own pair of prices.
Enter prices above to see how the whole market compares with any single book.
Negative synthetic hold: stake split
The best prices imply less than 100% combined. At these exact quoted prices, splitting a total stake as below returns the same amount whichever side wins. In practice, quotes go stale, books limit or void bets they consider errors, stake caps can leave one side unfilled, and settlement rules differ between books. Check every price is current before treating this as anything more than a market observation.
How it's calculated
book hold = 1 − 1 / (implied A + implied B)
synthetic hold = 1 − 1 / (lowest implied A across books + lowest implied B across books)
consensus fair A = best implied A / (best implied A + best implied B)
Hold is a share of handle: the margin the market keeps, over time, from money bet on both sides in balanced proportions. Figures describe the prices you enter, not the probability of any outcome. Nothing is sent anywhere; the calculation runs entirely in your browser.