Vig (vigorish)

The built-in margin a sportsbook or market charges, reflected in prices that sum to more than 100 percent across outcomes. Stripping the vig reveals the fair, no-vig probability.

When the yes and no prices of a market add up to more than a dollar, the difference is the vig. Comparing a sportsbook's vig-inflated line to a no-vig fair price is a quick way to see whether a Kalshi contract offers a better number.

Vig, short for vigorish, is the built-in cost of placing a wager, the margin the house or the market structure takes regardless of who wins. In a sportsbook it appears as odds that do not quite add up to 100 percent across all outcomes. On an exchange like Kalshi, the equivalent costs show up as trading fees and the bid-ask spread rather than a hidden margin in the line.

Understanding vig matters because it raises the bar your edge has to clear. If every round trip costs you a few cents between fees and crossing the spread, a trade that looks barely positive on probability alone can be negative after costs. The more often you trade, the more total vig you pay, which is why high-frequency strategies live or die on fee efficiency.

Exchanges are generally cheaper than traditional books because you can often add liquidity instead of taking it, and because fees are transparent rather than baked into a line. But the cost is never zero, so factoring vig into every trade is the difference between a strategy that looks profitable and one that actually is.