How NetArbs works

The same bet has different prices

Sportsbooks set their own odds, so the same moneyline, spread, total or player prop is priced differently from one book to the next. NetArbs collects the prices from 30 sportsbooks, exchanges and prediction markets and lines them up side by side, so the best price on every side is one look away. Taking the best price every time is called line shopping, and it is the cheapest edge in betting.

The vig, and how it is removed

Every price includes the book's margin, called the vig or juice. At -110 on both sides of a bet each side implies a 52.4% chance, 104.8% in total. A fair coin is 50/50; the extra 4.8% is what the book keeps.

Removing the vig ("de-vigging") turns the two prices back into probabilities that add up to 100%. On -110/-110 every method gives 50%. Away from even money the methods disagree, because books load more of their margin onto the longshot: at -150/+130, taking the margin off in proportion (multiplicative) puts the favourite at 58.0%, while the power method, which takes more off the longshot, puts it at 58.4%. NetArbs uses the power method by default and lets you switch to additive, multiplicative or the most conservative of the three.

The fair price comes from the sharp books

A fair probability is only as good as the prices it is taken from. NetArbs de-vigs the books that are measured to be accurate on that sport and market, and takes the median across every one of them that quotes the same player, stat and line. Each price shows how many books are behind it.

DFS and pick'em apps never set a fair price. Their lines are the offer being judged, not the evidence: a prop is priced from the sportsbooks first, and only then compared with what the app pays.

+EV on pick'em apps: the break-even

A pick'em slip pays a fixed multiple when every leg hits, so each leg has a break-even hit rate. A 2-pick PrizePicks Power Play pays 3x, so each leg must hit 57.7% of the time to break even; a 2-pick on Underdog pays 3.5x, a break-even of 53.5%; a 6-pick PrizePicks Power Play pays 37.5x, 54.7% per leg.

A leg is +EV (positive expected value) when its de-vigged fair probability is above that break-even. DFS Studio lists those legs and builds slips from them; the desktop app can fill the slip in your account and always stops before Submit.

Beating the closing line

The closing line, the price just before a game starts, is the market's last and best-informed estimate. A bet placed at a better price than the close was a good price by the market's own final judgement, so closing-line value (CLV) shows whether bets are +EV long before enough results come in to tell skill from luck. Every bet you log is re-priced at its own line until kickoff, to show whether the market moved toward it.

Prediction-market arbitrage

Kalshi, Polymarket and Limitless list many of the same questions. When YES on one and NO on another cost less than $1.00 together, buying both pays $1.00 whichever way it resolves. NetArbs finds those pairs with each venue's fees included, and only where both contracts settle on the same event.

What it does not do

NetArbs does not predict outcomes and does not guarantee winnings: a +EV bet loses often, and the edge only shows over many bets. It never places a bet for you. Bet only where it is legal for you, and only what you can afford to lose.