The Lab · Foundations · updated 2026-10-22
What a betting line really says
A moneyline isn't a prediction — it's a price. Learning to read -157 as a probability is the first skill in evaluating any betting market.
A moneyline is a price, not a prediction. Convert it to the win rate it demands, take out the bookmaker's fee, and you have the market's honest opinion — which, on our own board, has kept its word for well over a thousand games.
Record figures marked as today's come live from the public record, refreshed as games are graded — as of Oct 30, 2026. Numbers we published on earlier dates stay as written, dated, so you can check them against today's.
Detroit -157. Kansas City +135. Most people read that as "Detroit is going to win." The market is saying something more precise, and more useful: it's quoting you a price — and every price implies a probability.
Converting a line to a probability
American odds answer one question: how much do I win on a bet?
- Negative number (-157): you must risk 157 to win 100. The favorite.
- Positive number (+135): you risk 100 to win 135. The underdog.
To find the win probability a price implies, divide what you risk by the total returned if you win:
| Line | Math | Implied probability |
|---|---|---|
| -157 | 157 / (157 + 100) | 61.1% |
| -110 | 110 / (110 + 100) | 52.4% |
| +100 | 100 / (100 + 100) | 50.0% |
| +135 | 100 / (100 + 135) | 42.6% |
| +150 | 100 / (100 + 150) | 40.0% |
That's the break-even rate: bet -157 all season, and you need 61.1% of those bets to win just to get your money back. One conversion, and a wall of odds becomes a list of probabilities you can argue with.
The two sides don't add up — that's the fee
Take Detroit -157 and Kansas City +135 in the same game: 61.1% + 42.6% = 103.7%. Real probabilities sum to 100%. The extra 3.7 points is the vig — the bookmaker's margin, baked into the prices so the book profits whichever side wins.
Strip it out (divide each side by the total) and you get the market's fair estimate: roughly 58.9% Detroit, 41.1% Kansas City. That de-vigged number is the market's actual opinion — and it is the number our board publishes on every game.
Why the line is worth respecting
A line isn't one analyst's guess. It opens from professional oddsmakers and then gets corrected by everyone willing to put money on a disagreement. Bet on a mispriced line and you move it toward the truth; the price you see has already absorbed thousands of those corrections. When we first wrote this in July, our graded board had a few hundred games and the favorites had won within about a point of what their prices claimed. Today it's 1,595 games: favorites have won 59.7% against 58.6% claimed, in public, every call published before the game. (Every figure we've published, dated.) When a line and your gut disagree, the line has the better track record.
What this doesn't tell you
The implied probability tells you what the market charges, not what's true. Lines carry the vig, they can lag news for a few minutes, and one book can drift from the other nine — those gaps are the entire hunting ground for a value bettor. But you can't spot a wrong price until you can read what the price says. This conversion is that first skill: every line is a claim, and claims can be checked.
Model output is informational and entertainment content, not betting or financial advice. If you bet, bet what you can afford to lose.
Log what you actually bet — units and dollars — and see it graded beside a model that publishes every call it makes, wins and losses alike. Free, no card.
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