Vig Calculator: Calculate the House Edge on Any Market

Vig — the margin sportsbooks build into every line — is the single largest cost bettors face over time. Enter odds from both sides of any market into the vig calculator, and it returns the vig percentage, the overround, and the no-vig implied probabilities that reveal the book’s true opinion.

How Do You Use the Vig Calculator?

Enter the odds for both sides of a two-outcome market — a point spread, moneyline, or a YES/NO prediction market price — into the vig calculator. It accepts American, decimal, and fractional formats, and instantly returns four numbers: each side’s implied probability, the total overround, the vig percentage, and the no-vig fair odds.

1. Each side’s implied probability — The raw probability embedded in the odds before vig removal
2. Total implied probability (overround) — The sum of both sides. Anything above 100% is the book’s margin
3. Vig / hold percentage — The effective commission extracted from both sides combined
4. No-vig implied probabilities — The true probabilities after removing the book’s margin proportionally

These no-vig numbers are critical for identifying value. If you estimate a side’s true probability at 58% and the no-vig line prices it at 52%, you have a 6-point edge. If the no-vig price is already 58%, there is no edge regardless of how the raw odds look. For a full breakdown of this concept, see our guide on what vig is and how sportsbooks use it.

How Does the Vig Calculation Work?

The math is straightforward: convert both sides of a line to implied probability, sum them, and measure the excess above 100%. That excess is the overround, and dividing it by the total gives the actual hold — the percentage of total handle the book keeps regardless of which side wins.

Notice that vig is not constant. Lopsided lines (-200/+170) can carry more or less vig than the standard -110/-110 depending on how each book prices the spread. The calculator reveals this instantly, while mental math gets unreliable on non-standard lines.

Why Does Vig Matter for Your Betting Results?

Vig is the headwind every bettor faces before a single game is played. A 52.4% win rate merely breaks even at standard -110 juice — anything below that loses money long-term, and every additional percentage point of vig raises that break-even threshold further out of reach for a typical bettor.

At volume, the differences compound. A bettor placing 500 wagers per year at $100 average stake:

• At 4.5% vig: $2,250 paid in margin annually
• At 6.0% vig: $3,000 paid in margin annually
• At 3.0% vig: $1,500 paid in margin annually

That $1,500 difference between a high-vig book and a low-vig book is pure profit retained. Shopping lines across multiple sportsbooks compresses effective vig by 1-2 percentage points per wager. Our dataset of 149,000+ historic games from 2007-2022 across six major sports confirms this pattern — vig is not a flat 4.5% everywhere but varies meaningfully by book and sport. See the full vig breakdown by sport for the complete figures. Use the odds converter to compare pricing across formats, and check the Odds Reference dashboard for real-time line comparisons.

How Does Vig Compare to Prediction Market Fees?

Prediction markets do not embed vig the same way sportsbooks do. On platforms like Polymarket and Kalshi, prices are set by traders in an order book, not imposed by a bookmaker, so the overround you’d calculate reflects natural bid-ask spread rather than a mandated house margin.

Instead, prediction market platforms charge explicit fees. As of our July 19, 2026 verification against Odds Reference’s Kalshi and Polymarket platform profiles, Kalshi charges roughly 1-2 cents per contract on entry and exit — a flat cost regardless of price — while Polymarket charges about 2% of net winnings at settlement, applied only to winning positions. Kalshi is a CFTC-regulated exchange; you can confirm its registration on the CFTC’s public site. Confirm current rates directly with each platform before trading, since fee schedules move without notice.

The vig calculator helps bridge this comparison. Enter both sides of a prediction market event (YES price and NO price from the same platform) to see the effective spread. If YES trades at $0.52 and NO at $0.51, the combined cost of $1.03 implies a 3% overround — comparable to a tight sportsbook line, though that spread doesn’t include the platform’s separate settlement or per-contract fee. Use the fee calculator to model those costs directly, and see our full prediction market fee comparison for worked examples at multiple contract prices.

Understanding your true cost per wager — whether that is sportsbook vig or platform fees — is foundational to calculating implied probability and identifying positive expected value.

Key Takeaways

• Vig is the overround above 100% when you sum both sides’ implied probabilities — the calculator computes this instantly for any odds format
• No-vig implied probabilities reveal the book’s true opinion, stripping away the margin and exposing where value exists
• The difference between a 3% vig book and a 6% vig book costs a 500-bet-per-year bettor $1,500 annually
• Prediction markets replace traditional vig with explicit fees — Kalshi charges roughly 1-2 cents per contract, Polymarket about 2% of net winnings (fee figures verified July 19, 2026) — but the calculator still measures the effective spread on any two-sided market
• Line shopping remains the simplest way to reduce effective vig — compare odds across books before placing any wager

Vig and platform fees are a real, ongoing cost of betting or trading, not a one-time consideration. If betting is affecting your finances or well-being, visit Odds Reference’s responsible gambling resources or call 1-800-522-4700.