How NegativeEV works
NegativeEV is a bet checker. Paste in a bet, or upload a screenshot of the slip, and every leg is graded against thousands of simulated games. The simulated win rate is then compared to the probability the price implies. The gap between the two is the verdict: Positive EV, Negative EV, or Roughly Fair.
Written by Jesse, NegativeEV. Last updated 8 August 2026.
What happens when a bet is checked?
The bet is matched to today's slate, graded against the simulated games, and priced against the odds on the slip.
- Submit a bet. Type it out, or upload a screenshot of a bet slip. The slip is transcribed and then discarded.
- Every leg is matched to a game on today's slate and graded against that game's simulated outcomes.
- The simulated win rate is compared to the probability implied by the price. A written read explains what is driving the gap.
How does the simulator work?
Every game on the slate is played out thousands of times before it starts.
Each sport has its own machine-learning models, trained on years of that sport's results. The models drive every play of every simulated game. What comes out is a distribution of outcomes for the game and for the players in it. A bet's simulated win rate is how often that bet won across those simulations.
Which sports does NegativeEV cover?
MLB, WNBA, PGA, and ATP.
| Sport | Bets that can be checked |
|---|---|
| MLB | Moneylines, run lines, totals, team totals, and player props: hits, home runs, strikeouts, total bases and more |
| WNBA | Moneylines, spreads, totals, and player props: points, rebounds, assists, threes, and points-rebounds-assists |
| PGA | Outrights, top 5, top 10 and top 20, make the cut, head-to-heads, and birdies by round |
| ATP | Match winner, total games, set and game handicaps, a player's games won, straight sets, and any tiebreak |
Parlays are covered too. Each leg is graded, then the ticket is priced as a whole.
Can a bet be checked after the game starts?
Yes. A game that is already underway is graded against the simulations from before it began.
That read is a pre-game projection, not a live one, and it says so. It names the game that already started. It stops once that slate re-simulates.
Is NegativeEV free?
Yes. 10 free checks a day with no account, and unlimited checks once signed in.
Signing in is free. The free checks reset daily at midnight Pacific. Signed-in checks carry a pace cap per hour, so one account cannot flood the pipeline in a loop.
Does NegativeEV give out picks?
No. NegativeEV checks a bet somebody already has in mind.
It is not a tout service, an odds screen or an arbitrage scanner. There is no pick list and no claimed record. The output is a probability next to a price, and what to do with that is the user's call.
What does the simulator not know?
Anything that happens after a slate is simulated.
A lineup change or a late scratch is not in the numbers until that slate re-simulates. A bet that cannot be matched to a simulated game comes back ungraded rather than guessed at. And a good price still loses often. The verdict is about the price, not about tonight.
Can a bet be checked on X?
Yes. Tag @shoulditail in a reply under a bet slip and the same verdict comes back as a reply.
The ground rules are at https://negativeev.com/about/x-bot
Related reads: the questions people arrive with, how accurate a simulator can be, tailing a pick from a post, why NegativeEV exists, how sim-grading works, and pricing a parlay leg by leg.