A longshot is a bet the sportsbook prices as unlikely to win — which is exactly why it pays a lot when it does. You'll hear the word in horse racing, football, basketball, politics, and even awards shows. But the idea is always the same: low probability, high reward.
Understanding what a longshot really is matters more than most bettors realize, because the same word describes two very different things — a bet that's simply unlikely, and a bet that's actually mispriced. This guide covers both.
Where the term comes from
The phrase comes from the racetrack. In early horse racing, a horse given long odds against winning was called a "long shot" — the bookmaker was taking a shot, and the odds were long. Over time the term slipped into everyday language, where "it's a long shot" means "it probably won't happen."
In betting today, a longshot simply means an outcome priced at long odds. There's no universal cutoff, but most bettors and books treat +400 (decimal 5.00, fractional 4/1) and beyond as the start of longshot territory.
How odds express a longshot
Odds look different depending on where you are, but they all say the same thing. Here's the same longshot bet in the three common formats:
| Format | Example | What it means |
|---|---|---|
| American | +400 | Win $400 on a $100 bet |
| Decimal | 5.00 | Total payout of $500 on a $100 bet |
| Fractional | 4/1 | Win $4 for every $1 staked |
The bigger the number, the longer the shot. A +150 underdog is a mild upset; a +1500 underdog is a genuine longshot; a +25000 longshot is close to a lottery ticket.
The math behind a longshot
Every set of odds implies a probability. The quick American-odds formula for a plus-money (underdog) price is:
Implied probability = 100 ÷ (odds + 100)
For a +400 longshot, that's 100 ÷ 500 = 0.20, or 20%. The book is telling you it thinks this outcome wins about one time in five.
Where you'll see longshots
- Moneyline underdogs — the simplest longshot: a team priced at +400 or more to win outright.
- Futures — a team to win a championship before the season starts. Almost every futures bet on a non-favorite is a longshot.
- Parlays and accumulators — combining several legs multiplies the odds, turning a group of modest bets into one long shot.
- Exotics — exactas, trifectas, correct-score, and "first goalscorer" markets all carry longshot pricing.
The appeal — and the risk
The appeal is obvious: a small stake can return a large payout. That's what draws people in. The risk is quieter but more important: longshots lose often, sometimes for long stretches, and the book's margin is stacked against you on every single bet.
That doesn't make longshots bad. It makes them a tool that needs a reason. The next question is always the same: are the odds paying more than the true chance of winning? If yes, it's value. If no, it's a donation to the book.
How to spot a longshot
- Look for big plus-money odds. +400 and up is the classic zone.
- Convert to probability. Use the formula above to see what the book is implying.
- Ask whether reality is better than the price. This is the step almost everyone skips — and it's the whole game.
Once you can read a longshot line and understand the probability behind it, you're ready to think about strategy. Read on: Longshot Betting Strategy.