NFL Win Probability Explained
What our numbers actually mean (and what they don't)
The Short Version
When we say the Chiefs have a 65% win probability, we're saying: if this exact game happened 100 times with these exact conditions, we'd expect Kansas City to win about 65 of them.
It's not a prediction. It's not a guarantee. It's our best estimate based on everything we can measure—home field, weather, injuries, recent form. The other team still wins 35% of the time. That's a lot.
What Goes Into the Number
We weight factors based on how predictive they've actually been over thousands of NFL games. Here's what matters most:
Home fieldis real. NFL home teams win about 57% of games, and that's been consistent for decades. Seattle's 12th Man, Arrowhead's noise, Lambeau in December—these aren't myths. We quantify how much each venue matters.
Weather changes everything in outdoor games. Remember the Bills-Colts snow game? Wind above 15 mph tanks passing efficiency. Cold makes the ball harder to catch. Rain means more fumbles. We check the forecast for every outdoor matchup.
Injuriesare tricky. Losing a starting QB is obviously huge—we've seen teams go from contenders to also-rans overnight. But we can't perfectly predict how backups will perform, and some injuries get hidden until game time.
Recent formcaptures momentum. A team that's won 5 straight is playing different football than a team on a 3-game skid, even if their overall records are similar.
Reading the Factor Breakdown
Every game page shows you which factors favor which team. We label them HIGH, MEDIUM, or LOW impact so you can see what's actually driving the number.
If you disagree with how we're weighting something—maybe you think a backup QB is better than we do, or the weather won't matter as much—that's useful information. Our model is a starting point, not gospel.
What We Can't Measure
Look, we can't quantify everything. Revenge games, contract years, locker room drama, a coach's job being on the line—these matter, but they're hard to put numbers on.
We also don't know about injuries until they're reported. A surprise inactive can swing a game 5-10 points. That's why our probabilities update as new information comes in.
Related Topics
Frequently Asked Questions
We're right about 57% of the time on games we call 60/40 or closer. When we show a team at 75%+, they win around 78% of those games. We track this because you should know when we're wrong.
New info came in. Maybe the injury report updated, or the weather forecast shifted. We recalculate whenever something material changes—that's the point.
We show our work. Most sites give you a number. We tell you why: home field is worth +3%, the weather's brutal for passing teams, their starting QB is out. You can disagree with our weighting—that's fine.
All the time. A 25% chance isn't zero—it's roughly 1 in 4. The 2007 Giants were underdogs against the Patriots. The 2021 Bengals made the Super Bowl as underdogs. Upsets aren't bugs, they're features.
Sources
Academic Research
- Massey, K. (1997). Statistical Models Applied to the Rating of Sports Teams. Bluefield College. Link
- Silver, N. (2012). The Signal and the Noise: Why So Many Predictions Fail—but Some Don't. Penguin Press.
Data Sources
- Pro Football Reference - NFL team statistics, historical data, and home/away records
- NFL.com Injury Reports - Official injury designations and player status
- NFL Weather - Game-day weather forecasts for outdoor stadiums
- NFL Football Operations - Official league analytics and research