No-Vig Calculator: True Odds & Fair Odds

What This No-Vig Calculator Does

Posted odds at any sportsbook bake in the book's margin. A line of 1.91 / 1.91 looks like a coin flip, but the implied probabilities (52.36% and 52.36%) sum to 104.71%, not 100%. The extra 4.71% is the vig, the bookmaker's commission. To find the true probability of each outcome, you need to remove the vig and redistribute the probabilities so they sum to exactly 100%.

This calculator does that automatically. Enter the posted odds in any format (decimal, American, or fractional), pick a devig method, and you get the true probability and fair odds for each side, plus the overround so you can see how much margin the book is taking. The same tool works as a no-vig calculator, devig calculator, true odds calculator, and fair odds calculator, since all four describe the same operation.

How to Use It

1. Pick the market type. 2-way for moneylines, totals, point spreads, and binary contracts. 3-way for soccer 1X2 markets where a draw is possible.
2. Pick the odds format. Decimal (1.91), American (-110), or Fractional (10/11). The tool converts internally and outputs in the same format.
3. Enter posted odds. Use a sharp book like Pinnacle, PS3838, or BetIsn for the cleanest reference. Soft-book lines (DraftKings, FanDuel) carry too much retail-bias to be a good reference.
4. Pick a devig method. Proportional for balanced markets, Shin for heavy favorites, Logarithmic when unsure. Run all three and compare for high-precision work.

The Math: Three Devig Methods

All three methods take the same input (posted odds) and produce the same shape of output (probabilities that sum to 100%). They differ in HOW they redistribute the margin. The full derivations are in our devigging prediction markets guide; here is the short version:

Proportional (Multiplicative)

The simplest method. Each side's true probability is its implied probability divided by the sum of all implied probabilities: p_i = (1/odds_i) / sum(1/odds). Fast, intuitive, and accurate when the market is balanced. The default for most sharp-book devigging because Pinnacle's small margins make method choice nearly irrelevant on mainline markets.

Shin's Method

Models the bookmaker's pricing as a mix of public bets and informed (insider) bets. Solves for the insider proportion z that explains the observed overround, then strips it out. More accurate when one side is heavily favored, because the insider effect is asymmetric. Particularly useful on soccer 1X2 where the favorite-draw-underdog gap can be large.

Logarithmic Method

Distributes the overround using log-odds. Finds an exponent k such that raising each implied probability to the kth power produces a set that sums to 1. A middle ground between Proportional and Shin in most practical cases.

Implied vs Fair Probability: The Difference Matters

Implied probability (raw 1/odds) and fair probability (no-vig) often look similar on tight sharp-book markets, but the difference matters when you stack edges. A 2 percent edge measured against implied probability can be a 0 percent edge against fair probability, because the 2 percent you "see" is just the vig. Always compare your trade against fair (no-vig) probability, not implied.

Where to Find Sharp Reference Odds

The output of any devig calculator is only as good as the input. Sharp books with low margins produce cleaner fair-odds estimates because the vig is smaller, so devigging errors are smaller. Recommended sharp references in 2026:

• Pinnacle and its sibling PS3838: 2 to 3 percent margin on mainline markets. The standard reference for sharp bettors worldwide.
• BetInAsia: aggregator of Asian sharp books. Very tight on Asian-focused markets.
• BetIsn, Pin88, BetDEX: Asian sharp books that often quote first on niche markets.
• SX Bet: peer-to-peer exchange with effectively zero house margin, since prices are user-set. Best on US sports.

For a deeper read on which sportsbooks deliver the cleanest sharp prices and which to avoid as references, see our best sportsbooks for arbitrage betting guide and the sharp odds aggregator pillar that explains why blending multiple sharps beats any single book as a reference.

Common Use Cases

Value Betting

Devig the sharp book's line, then compare the no-vig probability to a soft book's odds. If the soft book is offering a price that implies a lower probability than the sharp's no-vig line, you have positive expected value. Repeat across thousands of markets and you have a value-betting system.

Arbitrage Detection

Take two venues' odds for the same outcome. Devig each. If the implied probabilities (after devigging) imply contradictory assessments of true probability, an arbitrage may exist. The full math is in our arbitrage calculator.

Kalshi and Polymarket Pricing

Convert a sharp sportsbook line into the fair price of a binary prediction-market contract. Devig the 2-way moneyline, multiply the favorite's no-vig probability by 100, and you have the fair Kalshi cents price. The Kalshi Fair Odds Calculator handles this with the Kalshi-specific fee adjustment baked in.

Frequently Asked Questions

What is a no-vig calculator?

A no-vig calculator (also called a devig calculator, true odds calculator, or fair odds calculator) removes the bookmaker's margin from posted odds to estimate the true probability of each outcome. Bookmakers price markets so the implied probabilities sum to more than 100 percent, and the excess is the vig (also called juice or overround). A no-vig calculator redistributes that excess back to exactly 100 percent so the result represents fair value.

What is the difference between no-vig odds and true odds?

They are the same thing. No-vig odds, true odds, fair odds, and devigged odds all refer to the same concept: the odds you would see if the bookmaker took zero margin. The price reflects only the implied probability of the outcome with no commission baked in. The terms are used interchangeably across betting forums and sharp-bettor literature.

Which devig method should I use?

Proportional (Multiplicative) is the simplest method and works well for balanced 2-way markets near 50/50. Shin is more accurate when one side is heavily favored because it models the impact of insider information. Logarithmic sits between the two and uses log-odds to distribute margin. For most sharp-book lines on mainline markets, all three give similar outputs within 0.5 percent of each other. The calculator above runs all three and you can compare. For automated devigging at scale, running all three and using the median is a robust default.

Can I use this for 3-way markets like soccer?

Yes. Toggle the 3-Way mode at the top of the calculator and three odds inputs appear (home, draw, away for soccer 1X2 markets, or any other three-outcome market). All three devig methods support 3-way input. Note that 3-way devigging is inherently noisier than 2-way because the vig is distributed across three outcomes; for high-precision work on 3-way markets, Shin or Logarithmic tend to be more accurate than Proportional, particularly when one outcome is much more likely than the others.

How is implied probability different from true probability?

Implied probability is the raw 1/odds reading from posted odds, before any margin adjustment. It includes the bookmaker's vig. True probability (also called fair probability or no-vig probability) is what you get after removing the vig. For example, Pinnacle posting 1.91 / 1.91 has implied probabilities of 52.36 / 52.36 percent (sum 104.71 percent, vig 4.71 percent). The no-vig probability is 50 / 50 percent because the actual market is a coin flip. Implied probability is good for quick reads; no-vig probability is what you compare against your own model or another venue's price to find value.

What is a fair odds calculator used for?

A fair odds calculator helps with three things: value betting (compare a soft book's odds to the fair odds derived from a sharp book to find positive expected value), arbitrage finding (detect when two venues' prices imply contradictory true probabilities, opening a guaranteed-profit window), and Kalshi/Polymarket pricing (convert sharp sportsbook lines into fair contract prices on prediction markets). The same fair-odds output supports all three workflows.

How does Claw Arbs use no-vig calculations?

Claw Arbs runs no-vig calculations live on every match across its 11-book sharp odds aggregator and individual sharp references (Pinnacle, PS3838, BetInAsia, SX Bet). The fair-odds output is the benchmark for every value-bet and cross-book arbitrage decision: soft books (Stake.com, BC.Game, Cloudbet, Bet105, Kalshi, Polymarket) are compared against the no-vig line, and the engine fires when the gap exceeds your minimum-edge threshold after fees and slippage.