No-Vig Calculator

What this no-vig calculator does

This calculator takes a two-way American-odds market — for example, NFL sides at −110 / −110, or an NBA moneyline at −180 / +150 — converts each side into its implied probability, calculates the vig (the amount by which those implied probabilities sum above 100 %), and returns the fair (no-vig) probability and fair American odds for each side. It is a probability analysis tool. It does not predict outcomes and it does not recommend bets.

How to use the calculator

1. Enter the American odds for both sides of a two-way market. Negatives indicate a favorite (−110 = bet $110 to win $100); positives indicate an underdog (+130 = bet $100 to win $130).
2. Optionally label the two sides for your own reference.
3. The output panel shows the vig, each side’s implied probability (with vig still in), each side’s fair probability (vig removed), and each side’s fair American odds.
4. Tap Copy summary to put the headline figures on your clipboard.

How the math works

The American-odds-to-implied-probability conversion is two formulas:

• If the odds are positive (e.g. +150): prob = 100 ÷ (odds + 100)
• If the odds are negative (e.g. −110): prob = |odds| ÷ (|odds| + 100)

So −110 implies 110 ÷ 210 = 52.38 %. A −110 / −110 market therefore has implied probabilities of 52.38 % + 52.38 % = 104.76 %. The 4.76 % overround is the vig — the bookmaker’s commission baked into the price.

To strip the vig out, divide each implied probability by the total implied probability. Each side then makes up its proportional share of 100 %. For −110 / −110, that yields 50 % / 50 % fair probabilities and +100 / +100 fair American odds.

For an asymmetric market like −180 / +150:

• −180 implies 180 ÷ 280 = 64.29 %
• +150 implies 100 ÷ 250 = 40.00 %
• Total: 104.29 % → 4.29 % vig
• Fair: 64.29 / 104.29 = 61.65 % for the favorite, 40.00 / 104.29 = 38.35 % for the underdog
• Fair American odds: roughly −161 / +161

What “vig” actually is

The vig (short for vigorish, also called juice, margin, or overround) is the bookmaker’s commission. By offering both sides of a market at prices whose implied probabilities sum to more than 100 %, the book guarantees itself a long-run profit assuming balanced action — and even if action isn’t perfectly balanced, the book’s risk-management desk shades lines to limit exposure.

A market with zero vig would be a true probabilistic price: a −110 / +110 line, where both sides return exactly the same expected payout as a coin flip would. Real markets always carry some vig because that is the book’s revenue model.

Typical vig ranges

Lower-vig books leave less margin for themselves and therefore offer sharper prices; higher-vig books carry more risk-management cushion and are typically used to fade public action. Two-book line shopping on a 4-5 % market can find 1-2 % of value; on a 20 % futures market the difference between books can be much larger because there is more margin to give back.

Why sharp bettors use no-vig lines

For a sharp bettor, the goal is finding markets where the true probability of an outcome differs from the price’s implied probability by enough to be a long-run win. The single best estimate of the true probability is the consensus no-vig line across several reputable books — because every book contributes a slightly different opinion and the market’s wisdom averages them.

The workflow:

1. Pull the same market from several books.
2. De-vig each book individually with a tool like this one.
3. Average the fair probabilities to get a consensus.
4. Compare the consensus against the book you intend to bet at.
5. If the book you’d bet at offers implied odds worse than consensus (i.e. lower implied probability), the bet has positive expected value relative to the market.

This calculator handles step 2. It tells you the market’s fair probability after the book’s commission is removed. It does not predict outcomes. It does not recommend bets. Even +EV bets lose frequently in the short run; variance and bankroll management matter more than any single line.

Privacy

This calculator does its arithmetic in JavaScript on your device. There is no fetch call, no analytics on the values you enter, no server-side logging. Your odds, labels, and any output stay on this device. The page works the same way offline once loaded.