Juice (or vig, short for vigorish) is the commission a sportsbook charges on every bet. It's built into the odds as the gap between the two sides' implied probabilities summing to more than 100%.
Standard juice: -110 / -110 for point spreads and totals. Each side implies 52.4%, summing to 104.8%. The extra 4.8% is the vig — the bookmaker's edge on a balanced market.
Vig calculation: Total implied probability = Implied(side A) + Implied(side B). Vig % = (Total implied − 1.0) / Total implied.
Low-vig books: Some books offer -105 / -105 lines (1.95% vig) or even juice-free markets. Over hundreds of bets, the difference between -110 and -105 is substantial. At -110, you need 52.4% win rate to break even; at -105, only 51.2%.
Reduced juice impact on ROI: Moving from -110 to -105 on 1000 bets of 1 unit each saves approximately 13 units purely from reduced vig — without improving your prediction accuracy at all. This is why line shopping is one of the highest-ROI activities in sports betting.
Juice-free formats: DFS contest formats, head-to-head matches, and some prop aggregators (PrizePicks, Underdog) use multipliers rather than traditional juice. Understanding the equivalent vig helps compare formats.