Football analytics tools you can run in the browser
Every calculator shows its formula and its constants. Nothing is hidden behind a number.
NFL win probability calculator
Score, clock, field position, down, distance, timeouts and the pregame spread in; a win probability out, from a model fitted on play-by-play.
RatingsElo rating calculator
Expected result, margin multiplier and rating shift for any game, with the formulas shown.
ConversionSpread and moneyline converter
A point spread as a win probability and a fair price, and the margin inside any pair of prices.
Daily quizGuess the win probability
Five real 2025 NFL snaps a day. Your guess against the model, graded by the final score.
DataNFL power ratings board
Elo, Markov and Massey for all 32 teams, sortable, with season traces.
ExplainersStepped explainers
Five simulations that animate a model one step at a time.
BacktestElo backtest since 1999
Brier score, hit rate and home-field edge for every season.
How the calculators fit together
Each calculator answers one question a football analyst asks again and again. The Elo calculator shows how a single result moves two ratings, step by step, with the same formula that updates the weekly NFL board. The spread converter turns a point spread into a win probability and a fair price, and reads the margin inside any pair of prices, using the scatter of real NFL results around the closing spread. The win probability calculator prices a game state from the score, the clock, field position, down, distance, timeouts and the pregame spread, with every coefficient printed underneath.
The daily quiz turns the same model into a game: five real snaps from the 2025 season, a guess, the model’s answer, and the final score as the judge, all graded with the Brier score. The stepped explainers are the slow-motion versions of these ideas, with the simulation running in the page.
None of the calculators store what you type. They are built on public data and published formulas, and each page links the article that explains the method in full: Elo ratings, the point spread and building a win probability model.
Frequently asked questions
Are the calculators free to use?
Yes. Every calculator runs in the browser with no account and no data sent anywhere. The models and constants they use are published on the same page, and the underlying game data comes from the open nflverse releases.
How accurate is the win probability calculator?
On the 2025 season, held out from fitting, its Brier score was 0.158 against 0.250 for a coin flip. It is a transparent logistic regression, so it is less sharp than tree-based public models, especially in late goal-line situations.
Which Elo constants does the Elo calculator use?
The ones from FiveThirtyEight’s published NFL model: K = 20, 65 points of home field and a margin-of-victory multiplier that uses the winner’s pregame edge. The same constants drive the weekly NFL ratings board.
Why does the spread converter use a standard deviation of 13.2?
Across 7,017 NFL games from 2000 to 2025, final margins scattered around the closing spread with a standard deviation of 13.2 points. Hal Stern measured 13.86 in 1991. The converter lets you change the value.