--- title: "Sports Betting Analytics: The Numbers That Matter and How to Read Them" canonical: "https://0xinsider.com/learn/sports-betting-analytics-guide" datePublished: "2026-09-12" dateModified: "2026-09-12" description: "Implied probability, hold, expected value, closing line value, calibration, sample size and bankroll, each with the formula and what 411,770 Polymarket sports bets show about it." --- # Sports Betting Analytics: The Numbers That Matter and How to Read Them Last updated: 2026-09-12 Canonical: https://0xinsider.com/learn/sports-betting-analytics-guide Every sports bet is a price on a probability. Analytics is the habit of checking the price against the probability before you pay it, and checking your record against the price after. This guide covers the eight numbers that do that work, with the formula for each and what 411,770 large Polymarket sports bets show about how they behave in a real market. ## What sports betting analytics is for A sports bet has two parts: a probability and a price. The probability is how likely the outcome is. The price is what the market charges for it. A sportsbook writes the price as a line, -110 or +240. Polymarket writes it in cents, 52¢ or 29¢. Either way, the bet is good when the probability is higher than the price says and bad when it is lower, and nothing else about the bet matters. Analytics is the set of habits that keep those two numbers in view. Before the bet, it means turning the price into a probability and asking whether you believe it. After the bet, it means measuring your record against the prices you paid rather than against the results, because results over a season are mostly noise and prices are not. This guide covers eight numbers in the order a bettor meets them: implied probability, hold, expected value, closing line value, calibration, the win-rate trap, sample size and timing. Each section gives the formula and then what it looks like in the one sports market where every bet is public: Polymarket. 0xinsider records every large Polymarket sports trade, and three studies on this site measure these numbers across 411,770 of them. ## Implied probability: what a price or a line says Every price is a probability in disguise. For negative American odds, divide the odds by the odds plus 100: -110 is 110 divided by 210, or 52.4%. For positive odds, divide 100 by the odds plus 100: +300 is 100 divided by 400, or 25%. Decimal odds are simpler: one divided by the odds, so 1.91 is 52.4% and 4.00 is 25%. A Polymarket price skips the conversion. A contract pays $1 if the outcome happens and nothing if it does not, so a price of 52¢ is a 52% implied probability and a price of 25¢ is 25%. Reading a Polymarket sports board is reading a column of probabilities, which is one reason bettors who move over from sportsbooks find their own thinking gets clearer. The implied probability is the market's estimate, and the whole question of whether to bet is whether yours is different. A bettor who cannot say what probability they believe has no basis for the bet. Write it down before you look at the price. ## Hold: what the market charges to play Add the implied probabilities of every outcome and a fair market sums to 100%. Anything above that is what the market keeps. A standard sportsbook line of -110 on both sides of a spread sums to 104.8%, so the book's hold is 4.55% of every dollar wagered whichever side wins. A three-leg parlay paid at 6 to 1 on three -110 legs sums to 112.5%. The parlay is the same bets, charged more. On Polymarket there is no line to shade, so the hold has two visible parts. The first is the spread between the best bid and the best ask. Across 0xinsider's sports trades from April to July 2026, the median spread at the moment of a large buy was one cent in every sport and every timing bucket, so a buyer crossing the book at 50¢ pays about half a cent above the midpoint, 1% of the stake. The second is the taker fee, which Polymarket sets per category: the sports rate is 0.05 times the share count times the price times one minus the price. At 50¢ that is 2.5% of the stake; at 90¢ it is 0.5%. So a taker buying both sides of a Polymarket sports market at 50¢ pays about 103.5% of the payout, against 104.8% at a -110 sportsbook, and the top tier of Polymarket's taker rebate program returns half the fee. A resting limit order pays no fee and earns the spread instead, so a maker's hold is zero. The guide at 0xinsider.com/learn/polymarket-fees-explained has the full schedule. The practical rule is the same at any venue: know your hold, because it is the edge you have to clear before you are ahead. ## Expected value: the only number that decides a bet Expected value is what a bet returns per dollar, on average, if it were placed many times. For a binary contract it is the probability you believe divided by the price you pay, minus one. Believe 55% and pay 50¢ and the expected value is plus 10%: a dollar staked returns $1.10 on average. Believe 55% and pay 60¢ and it is minus 8.3%. Everything in this guide serves that formula. Implied probability gives you the price side. Your model, your read, or the sharp money gives you the probability side. Hold tells you how far above zero the expected value has to sit before fees before you are actually ahead. A bet with positive expected value can lose, and a bet with negative expected value can win, and neither result tells you which kind of bet it was. The practical habit is to refuse a bet whose expected value you cannot state. If you believe the home side is 55% and the price is 55¢, there is no bet, however strongly you feel about the team. If the price is 48¢ there is a bet whether or not you like the team. ## Closing line value: how professionals grade themselves Results take a season to mean anything. The price does not. Closing line value is the difference between the price you paid and the price the market settled on at kickoff, and it is how professional bettors measure themselves week to week. Buy at 48¢ and watch the market close at 55¢ and you have seven cents of closing line value, whether or not the team wins. The logic is that the closing price is the market's best estimate, with every lineup, injury and sharp opinion priced in. If you consistently buy below it, you are consistently buying outcomes for less than they are worth, and over enough bets that turns into profit. If you consistently buy above it, you are the bettor the professionals are trading against. The guide at 0xinsider.com/learn/closing-line-value works through the formula, the sign convention and the fee adjustment. On 0xinsider the pick of the day at 0xinsider.com/pick-of-the-day records the entry price and the closing price for every pick, so its closing line value is public before the game is played. ## Calibration: does the price mean what it says A market is calibrated when outcomes priced at 60¢ happen 60% of the time. It is the first thing to check about any market you plan to bet in, because if the prices are systematically wrong in one direction, that direction is a free edge, and if they are not, your edge has to come from somewhere else. 0xinsider ran that check across 411,770 Polymarket sports buys of $1,000 or more from April 2 to September 11, 2026. Buyers paid 60.6¢ on average and won 60.7% of the time. Split into ten price buckets, every bucket from 20¢ to 98¢ sat within a point and a half of its price, with confidence intervals that include zero. The one exception was buys under 10¢, which won 2.97% of the time at an average price of 6.49¢ and returned 39 cents on the dollar. The full study is at 0xinsider.com/research/favorite-longshot-bias-polymarket-sports. Its conclusion for a bettor is direct: on a Polymarket sports market, the price is a fair estimate, and the only systematic mispricing worth the name is the longshot under a dime. There is no line to beat. Whatever edge you have has to come from knowing something the price does not, or from knowing who is on the other side. ## The win-rate trap Win rate is the number every bettor quotes and the one that says least. A bettor who only backs 90¢ favorites wins 90% of the time and has demonstrated nothing, because the market already priced those outcomes at 90%. A bettor who backs 30¢ underdogs and wins 35% of the time has beaten the market by five points and looks, on win rate alone, like a loser. The chart below is the same 411,770 sports buys, with the average price paid in each bucket beside the share of buys that won. The two bars match all the way up. Win rate is the price you like to pay. The number that measures skill is the gap between the two bars, which is the calibration edge, and it is what 0xinsider grades wallets on. When someone shows you a record, ask for the average price. A 60% record at an average price of 55¢ is a five-point edge. A 60% record at an average price of 62¢ is a two-point loss. Without the price, the record is a story. ## Sample size: why 100 bets prove nothing A bettor whose true win rate at even money is 55%, which is an excellent rate, will over 100 bets post anything from 45% to 65% about 19 times in 20. Over 500 bets the range is 50.6% to 59.4%. It takes roughly 2,500 bets before the measured rate sits within two points of the truth, and a two-point edge is a very good edge. That is the binomial formula, and it is the reason results are a poor guide and prices a good one. Closing line value shows through in a few dozen bets because the closing price is a fact, not a sample. Win rate needs thousands. Any tipster, tout or wallet with a 200-bet record is showing you a sample too small to distinguish skill from a good month. 0xinsider's grades are built for this problem. A wallet's grade shrinks toward the average when its record is short and moves away from it as the record lengthens, so a wallet with twenty winning trades gets a C, not an S. The method is explained at 0xinsider.com/learn/how-bayesian-confidence-scoring-works. ## Timing: the price depends on when you bet The same bet costs a different price at different times. A sportsbook line opens soft and tightens toward kickoff as money and information arrive. A Polymarket sports market does the same and then keeps trading through the game. 0xinsider timed 396,830 large Polymarket sports buys against kickoff. Half landed after the game had started. Buys placed one to seven days before kickoff lost to the price by 3.21 points, and the confidence interval clears zero. From six hours out through the final whistle every bucket was calibrated. Early money was paying an average quoted spread of 18¢ a week out against one cent on the day, and it was wrong more often than the price said. The study is at 0xinsider.com/research/when-large-sports-bets-land, and the guide at 0xinsider.com/learn/line-movement-sports-betting-explained covers how to read a moving price. The analytics point is simple: your closing line value depends on when you bet, and the data says early is expensive. ## Who is on the other side Every bet has a counterparty, and on Polymarket the counterparty has a public record. 0xinsider grades every wallet from S to F on its settled history. Across 155,832 sports buys from June to September 2026, wallets graded S, A or B beat the price they paid by 1.25 points and wallets graded D or F lost 1.21. The gap held in every price bucket and every market type, and almost all of it opened after kickoff: before the game the cohorts were within a point of each other, and in-play they were four and a half points apart. That is a piece of information no sportsbook customer has. On a Polymarket sports board you can see which side the profitable wallets are on for a given game, how much they have on it, and whether they took it before kickoff or during play. The study is at 0xinsider.com/research/sharp-money-polymarket-sports. Use it as a probability input, not as an instruction. A game where the S, A and B wallets are 70% on the home side at 52¢ is a game where your 55% belief has company. A game where they are on the other side is a game to look at again. ## Bankroll: sizing so variance cannot end you An edge only pays if you are still betting when it arrives, and the sample-size math above says it arrives slowly. The Kelly criterion gives the stake that grows a bankroll fastest for a known edge: edge divided by the odds. For a 55% belief at a 50¢ price, that is 10% of the bankroll. In practice nobody knows their edge to the point, so most professionals bet a quarter to a half of Kelly and accept slower growth for a smaller chance of ruin. Two rules follow. Never let the size of a bet depend on how you feel about it, because feeling is the part of you the market prices best. And never let the size of a bet depend on how the last one went. The guide at 0xinsider.com/learn/how-to-use-kelly-criterion-prediction-markets works through the formula with Polymarket prices. ## Where each number lives on 0xinsider Implied probability is the price on every Polymarket market and every 0xinsider sports board: 0xinsider.com/sports/nfl, 0xinsider.com/sports/nba, 0xinsider.com/sports/soccer, 0xinsider.com/sports/tennis, 0xinsider.com/sports/mlb, 0xinsider.com/sports/nhl, 0xinsider.com/sports/ufc and 0xinsider.com/sports/esports. Each board shows the moneyline, spread and total markets for each game, the kickoff countdown, and the live score once the game starts. Calibration edge and win rate sit side by side on every trader profile, with the realized P&L and the positions the wallet holds now, and the grade that combines them. The leaderboard at 0xinsider.com/leaderboard ranks wallets by that record. The guide at 0xinsider.com/learn/prediction-market-trader-grades-explained covers what each letter means. Who is on the other side is the sharp money strip on each game on a sports board, and the whale alerts feed at 0xinsider.com/whale-alerts, which shows every large buy as it lands with the buyer's grade beside it. Timing is the timestamp on each of those alerts. Closing line value is recorded for every pick at 0xinsider.com/pick-of-the-day, and the parlay side of the market is the combos ledger at 0xinsider.com/combos. Custom alerts on a wallet, a market or a game are covered at 0xinsider.com/learn/how-to-set-up-custom-trade-alerts. ## Frequently Asked Questions What is sports betting analytics? The practice of turning every price into a probability before a bet and measuring every bet against the price paid afterward. The core numbers are implied probability, hold, expected value, closing line value, calibration and sample size. How do I convert American odds to a probability? For negative odds, divide the odds by the odds plus 100: -110 is 52.4%. For positive odds, divide 100 by the odds plus 100: +300 is 25%. A Polymarket price in cents is already the probability. Is win rate a good measure of a sports bettor? No. Win rate follows the prices a bettor pays: a bettor who backs 90¢ favorites wins about 90% of the time. The measure of skill is the gap between win rate and the average price paid, which is the calibration edge. How many bets before a record means anything? At a true 55% win rate, the measured rate lands within ten points of the truth over 100 bets and within two points over about 2,500. Closing line value shows skill in far fewer bets because the closing price is a fact rather than a sample. Are Polymarket sports prices accurate? Across 411,770 large buys from April to September 2026, buyers paid 60.6¢ on average and won 60.7% of the time. Every price bucket from 20¢ to 98¢ was within a point and a half of calibrated. Buys under 10¢ won far less than their price. What does 0xinsider add to sports betting analytics? The counterparty. Every Polymarket wallet has a public record, 0xinsider grades it, and the sports boards show which side the profitable wallets are on for each game, before kickoff and during play.