Sports betting questions

About 52.4%. At −110 you risk 110 to win 100, so you have to win 11 bets for every 10 you lose just to get your money back.

The vig, or juice, is the bookmaker’s cut, built into the prices. When both sides of a bet are −110, the two prices add up to more than a fair bet would, and the difference is what the book keeps: about 4.5% of the money staked.

Far more than single bets. Every leg you add multiplies the bookmaker’s margin: with legs at −110 a parlay costs about 9% with two legs, 13% with three and 21% with five, against 4.5% for a single bet.

No. Raising the stake after every loss wins a little most of the time and now and then loses the whole bankroll. It cannot change the price of the bets, so on average you still lose the bookmaker’s margin on everything you stake, and a bettor with a real edge is safer without it.

Yes, if each bet is too big a share of your bankroll. An edge shows only over hundreds of bets, and a losing run long enough to empty the bankroll can come first. The smaller the stake next to the bankroll, the rarer that is.

Thousands. Over a few hundred bets luck is bigger than any realistic edge: a bettor with no skill often shows a profit, and a bettor with a real edge often shows a loss.

Your edge divided by the net odds, as a share of your bankroll: 5.5% for a bettor who wins 55% at −110. Most bettors who use it stake half or a quarter of that, because the full stake swings hard and is too big whenever the real edge is smaller than the estimate.