Website Help

Frequently Asked Questions

Some common questions you may have about the calculations on our website

• 1. HOW DO YOU RANK TEAMS?

  We have a fantastic set of metrics on our Rankings page. For a straight up team ranking, we compare the strength of their schedules. We believe this gives us a much more robust and accurate ranking than a simple win-loss record. Significant weight is given to a team's own performance. Opponent wins are included, but we exclude the wins and losses they have against the team. Finally, the team's point difference is included to give teams with large victory margins a boost. Team ranking is calculated using the following formula:
  
  Team Ranking = (Team Wins * 10) + Opponents Wins [in all other games] + (Team Point Difference * .20) / Team Games Played
  
  For ATS rankings we create a composite ranking by combining three metrics—ATS Win Percentage, ATS Win Margin, and ATS RPI. We normalize and weight each of the components. We believe this is a powerful way to get a holistic view of a team's betting value. It is obtained by calculating:
  
  ATS Team Ranking = (Win PCT * 45) + (ATS Margin * 35) + (RPI * 20)
  
  The higher the numbers, the stronger we think the team is.

• 2. HOW DO YOU CALCULATE REL?

  The core idea of the Relativity Index is to combine two things into a single number: a team's own performance (how much they outscored their opponents on average) and the quality of their opponents (how good their opponents were when they played against everyone else). The index's purpose is to give a more complete picture of a team's strength than a simple point difference. A team with a high point difference might have just played a very weak schedule. This index tries to correct for that. The index is obtained by calculating:
  
  Relativity Index (REL) = Average PPG difference + Opponent Average PPG difference [in all other games]
  
  Where:
  
  Average PPG difference = Total Points Scored - Total Points Allowed) / Games Played
  
  For example, if the Seahawks score 35.0 Points Per Game (PPG), and their opponents give up 20.0 PPG in all of their other games, then the Seahawks are +15.0 PPG on offense. If they give up 20 PPG, and their opponents score 25.0 PPG in all of their other contests, then the Seahawks are +5.0 on defense. This means the Seahawks have a Relativity Index of +20.0.
  
  A higher number is better. You would compare the Seahawks' REL of +20.0 to another team's REL (e.g., the 49ers' REL of +15.0) to conclude that the Seahawks are a better team.

• 3. HOW DO YOU CALCULATE PRD?

  Passer Rating difference is obtained by subtracting a team's Defensive Passer Rating from its Offensive Passer Rating. This statistic has proven to have a direct, and incredible, correlation to victory and championship success, straight up. Teams with a high Passer Rating difference are successful. Teams with a low Passer Rating difference are not successful. It is calculated using the following formula:
  
  Passer Rating Difference (PRD) = Team Offensive PR - Team Defensive PR
  Passer Rating (PR) uses the NFL formula: ((A + B + C + D ) / 6) * 100
  
  Where:
  
  A = ((Completions / Attempts) - .3) * 5
  B = ((Yards / Attempts) - 3) * .25
  C = (Pass Tds / Attempts) * 20
  D = 2.375 - (Ints / Attempts * 25)
  
  If any of the above components are greater than 2.375 they are set to 2.375 and if any are less than zero they are set to zero.
  
  The maximum possible quarterback rating for the NFL is 158.3. A perfect rating requires at least a 77.5% completion rate, at least 12.5 yards per attempt, a touchdown on at least 11.875% of attempts, and no interceptions. The details of passer rating can be found here and the history can be found here.

• 4. HOW DO YOU CALCULATE ANYA?

  Adjusted Net Yards Per Attempt (ANYA) is a highly-regarded and more comprehensive passing statistic than simple yards per pass attempt. It's often cited in analytics as having a strong correlation with points scored and winning football games because it accounts for the most impactful plays in the passing game. We use it to measure a team's passing efficiency. It is calculated using the following formula:
  
  Adjusted Net Yards Per Attempt (ANYA) = (Pass Yards - Sack Yards) + (20 * Pass TDs) - (45 * Ints) / (Pass Attempts + Sacks)
  
  The higher the number, the more efficient a team's passing game is.

• 5. HOW DO YOU CALCULATE NPP?

  The value of the Negative Pass Play Rate is that it provides a direct measure of a team's or quarterback's ability to avoid the most costly outcomes of a passing play. It essentially answers the question: "How often does this team's passing game end in a disaster?". After all, sacks and interceptions are drive killers and can lead to lost games. The Negative Pass Play rate is calculated as:
  
  Negative pass plays (NPP) = (Sacks Suffered + Interceptions) / Pass Attempts
  
  The resulting number is the percentage of negative pass plays a team has in a given season A lower percentage indicates less mistake plays.

• 6. HOW DO YOU CALCULATE DPR?

  Our Disruptive Play Rating (DPR) is a measure of a defense's ability to create negative outcomes for the opposing offense. This rating measures how much a teams defense disrupts the opponent's drive. Disruptive plays are highly correlated with future defensive success. You know all about how disruptive a takeaway or sack can be to an offense. We include Tackles For Loss (TFL) because they are the definition of a "disruptive play" against the run or a short pass. It stops the offense, reverses field position, and can throw off the play-calling rhythm of an offense. A team's Disruptive Play Rating is obtained by calculating:
  
  Disruptive Play Rating (DPR) = (Takeaways / Games) + (Sacks / Games) + (Tackles For Loss / Games)
  
  The higher number, the more disruptive a team's defense is. Note that for seasons prior to 2012 we do not include Tackles For Loss.

• 7. HOW DO YOU CALCULATE YPPA AND YPPS?

  Yards Per Point Allowed (YPPA) is a team-wide measurement of ability to keep opponents off the scoreboard, their bendability. It takes into account a variety of factors (including proficiency of defense, red zone defense, and turnover difference). A team's bendability is obtained by calculating:
  
  Yards Per Point Allowed (YPPA) = Yards Allowed / Total Points Allowed
  
  The higher the number, the more difficult a team makes it for opponents to score points.
  
  Yards Per Point Scored (YPPS) is a team-wide measurement of ability to turn yards into points, their scoreability. It takes into account a variety of factors (including proficiency of offense, red zone offense, and turnover difference). Other measures of offense, and offensive efficiency, look at the offensive unit in a vacuum, we don't. A team's scoreability is obtained by calculating:
  
  Yards Per Point Scored (YPPS) = Offensive Yards / Total Points Scored
  
  The lower the number, the more efficiently a team scores points.

• 8. HOW DO YOU CALCULATE WIN PCT?

  The Win Pct column represents a team's against the spread (ATS) winning percentage. This metric is a key indicator of team performance. You'll find it in several places throughout the website, such as in the Rankings table and in a visual comparison chart on the Standings page. Win percentage is calculated using the following formula:
  
  ATS Winning Percentage (WP) = Wins + (Pushes / 2)) / (Wins + Losses + Pushes
  
  From a pure betting analysis point of view you may exclude pushes from the total number of games you're evaluating. The game simply doesn't count towards the win/loss record for betting purposes.
  
  Betting Win Pct (BWP) = Wins / (Total Games Played - Pushes
  
  The key difference being the formula treats a "tie" or "push" as a no-action bet. However in official standings, a "tie" or "push" is a definitive result. It contributes to a team's record and is factored into their winning percentage for ranking purposes—that's why we include them
  
  Winning percentages are color coded into > 55% (green), < 50% (red) and between 50% and 55% (black).

• 9. HOW DO YOU CALCULATE AVERAGE MARGIN (MAR)?

  Average Margin (MAR) measures the average directional bias in the bookmaker's line for that team. It tells you whether the line tends to be too high or too low over time. MAR shows the number of points a team won or lost by in the season and it includes the point spreads in that calculation. For example, if the Seahawks were 10-point favorites over the Browns and ended up winning by 20, then the Margin would be 10. If the Seahawks had won by 5 points, on the other hand, the margin would be -5. It is calculated using the following formulas:
  
  Margin = Final Score Margin - Point Spread
  Average Margin (MAR) = Total Margin / Total Games Played
  
  The Average Margin (MAR) measures bias (directional error).

• 10. WHAT IS PS?

  Our Predictability Score (PS) measures the degree to which a team's results consistently deviate from the market's pre-game expectations. Essentially, PS is a proxy for the bookmaker's accuracy when setting the point spread (line) for a team's games. It is calculated as follows:
  
  PS = Average(|Final Score Margin - Point Spread|)
  
  Lower PS => Higher Predictability. The bookmaker has been highly accurate in setting the lines for this team, meaning the team's performance has been consistent and easier to project.
  Higher PS => Higher Unpredictability. The bookmaker has struggled to set accurate lines for this team, meaning the team’s results are often surprising, volatile, or prone to swings relative to the market expectation.
  
  The Predictability Score (PS) measures magnitude of error (volatility).

• 11. HOW DO YOU CALCULATE RPI?

  The Ratings Percentage Index (RPI) is measure a team's strength of schedule and how a team performs against that schedule. This index considers whether a team won or lost but not the margin of the victory. More weight is given to teams playing and winning games on the road. Teams with a high RPI are more successful. It is calculated using the following formula:
  
  Ratings Percentage Index (RPI) = (WP * 0.25) + (OWP * 0.50) + (OOWP * 0.25)
  
  Where:
  
  WP = Win Percentage
  OWP = Opponents' Win Percentage
  OOWP = Opponents' Opponents' Win Percentage
  
  To give more weight to teams winning on the road, away wins are treated as 1.4 wins, and away losses are treated as 0.6 losses. Home wins are treated as 0.6 wins and home losses are treated as 1.4 losses. Games in neutral sites counts as 1.

• 12. HOW DO YOU CALCULATE SPREAD TRENDS?

  We analyze a rolling three-year window of historical data, plus the current season, to calculate the performance of every point spread. Spread trends for weekly matchups are determined by two components, win percentage and margin of cover.
  
  Win Percentage Thresholds. First, we calculate the win percentage against the spread (ATS) for a SPECIFIC BETTING LINE as follows:
  
  ▪  If the home team's win percentage is greater than 55%, it's a home-favored trend.
  ▪  If the visitor team's win percentage is greater than 55%, it's a visitor-favored trend.
  ▪  If the home team's win percentage is between 50% and 55%, it's a neutral play, with a slight bias toward the home side.
  ▪  If the visitor team's win percentage is between 50% and 55%, it's a neutral play with a slight visitor bias.
  ▪  Anything else (i.e., a win percentage of 50% or less for both sides) is a neutral trend.
  
  Margin of Cover Thresholds. Second, we look at the average margin of cover for the home and visitor teams. This is the average number of points by which a team beat the SPECIFIC BETTING LINE. A positive number means the winning team covered the spread, while a negative number means they did not.
  
  ▪  If the winner's average margin of cover for a spread is greater than 1.5 points, it's a significant win margin.
  
  Game Classifications. To classify games we combine these two components to classify each game into a Spread Trend as follows:
  
  ▪  Strong-Home: The home team has a win percentage > 55% AND an average margin of cover > 1.5 points.
  ▪  Home: The home team has a win percentage > 55% but a margin of cover < 1.5 points.
  ▪  Strong-Visitor: The away team has a win percentage > 55% AND a margin of cover > 1.5 points.
  ▪  Visitor: The away team has a win percentage > 55% but a margin of cover < 1.5 points.
  ▪  Neutral-Home: The home team has a win percentage between 50% and 55% AND a margin of cover > 1.5 points.
  ▪  Neutral-Visitor: The visitor team has a win percentage between 50% and 55% AND a margin of cover > 1.5 points.
  ▪  Neutral: All other games are simply "Neutral" plays.
  
  Note that once a game is classified as a Neutral play by win percentage, a high margin won’t move it to Home or Visitor. Essentially, our calculation uses win percentage as the primary filter and margin of cover as a secondary filter to identify games with the strongest historical betting trends.

• 13. WHAT IS OS?

  We found a creative and interesting way to combine two key metrics to build a “matchup” statistic. Our Opportunity Score (OS) is a straightforward, easy-to-understand calculation used to measure rush or pass opportunity in a weekly matchup. By adding a team's offensive rushing ability, Rush Yards Per Attempt (RYPA), to their opponent's defensive vulnerability, RYPA Allowed, we have created a single number that quantifies the rushing opportunity for the visitor and home teams competing in an upcoming game.
  
  We do the same for Passing, using a team’s Net Pass Yards Per Attempt added to their opponent’s defensive Pass YPA Allowed. This is gross passing yards, minus yards lost via sacks, divided by passing attempts. We add in the number of sacks to the attempts because a sack is effectively an attempted pass. We believe net pass yards gives a far more accurate gauge of a team's ability to pass the ball.
  
  Rush Opportunity = Team RYPA + Opponent RYPA Allowed
  Pass Opportunity = Team NYPA + Opponent NYPA Allowed
  
  Where:
  
  Rush Yards per Attempt (RYPA) = Rush Yards / Carries
  Net Yards per Attempt (NYPA) = (Passing Yards - Sack Yards) / (Pass Attempts + Sacks Suffered)
  
  A higher number indicates a favorable rushing or passing matchup for the team.

• 14. WHAT IS EPA?

  Expected Points Added (EPA) is a measure of how many points a player or team contributes to their team's total score. It is calculated by looking at the expected points for a given situation (down, distance, and field position) and comparing it to the expected points after the play. The difference between the two expected points is the EPA for that play.
  
  We use EPA as a rate metric to evaluate team passing and rushing efficiency. By using EPA per attempt across the current season, we normalize the data ensuring a fair comparison between all teams. We then take the offensive EPA and subtract the defensive EPA allowed. Our Pass and Rush EPA differences are useful and predictive metrics, calculated as follows:
  
  Pass EPA = Offensive Pass EPA Per Attempt − Defensive Pass EPA Per Attempt Allowed
  Rush EPA = Offensive Rush EPA Per Carry − Defensive Rush EPA Per Carry Allowed
  
  These rate metrics provides a direct, context-aware measure of which team has the passing or rushing advantage, they can be found on the Matchups page.

• 15. CAN YOU TELL ME MORE ABOUT YOUR PREDICTION MODEL?

  Our game predictions are powered by a custom Machine Learning algorithm designed to identify betting value against the spread (ATS), on the Money Line (ML) or Straight Up (SU). We go beyond simple records and subjective analysis to find true, repeatable efficiencies in the market. Our Machine Learning algorithm is trained on a massive historical dataset, processing over 2.5 million unique data points which represent the combined, game-by-game trends and efficiency metrics across multiple NFL seasons.
  
  The Objective
  
  Our goal is to pick winners either ATS, on the Money Line or Straight Up. For ATS and SU analysis use historical data to determine which side of the spread has a greater than 50% chance of covering or winning. For Money Lines we identify where the odds provided by the sportsbook offer genuine value.
  
  The Engine
  
  The core of our system is a Logistic Regression algorithm. This is the most effective statistical tool for predicting the probability of a binary outcome. For every game, our model calculates the probability that the Home Team will cover the spread or win versus the probability that the Away Team will cover or win.
  
  The Output
  
  The model outputs a single number— the predicted probability of the outcome. Our methodology is 100% quantitative and objective; it incorporates absolutely zero subjective opinions or assumptions about teams, players, or matchups. The model simply processes the data. Associated with each NFL pick is a Confidence Rating from 1 to 5 stars. This rating is a straightforward reflection of the model's output: the more stars shown, the more the model favors its final prediction.

• 16. WHAT IS EXPECTED VALUE (EV)?

  In simple terms, expected value determines if a bet is profitable in the long run by comparing your perceived probability of an outcome against the probability reflected in the odds offered by the sportsbook. By focusing on +EV bets, you can identify situations where the payout is greater than the risk, giving you an edge over the long run. EV is a long-term concept. Individual bets can still result in losses due to variance, but consistently making +EV bets should lead to profitability over thousands of bets.The calculation requires three steps:
  
  1. Determine True Probability. Our proprietary prediction model calculates the probability of a team winning the game.
  2. Calculate Implied Probability and Payout Odds. Implied Probability is the hidden percentage chance the sportsbook assigns to the outcome, based on the odds they posted. We convert the money line odds into a decimal payout, which tells us exactly what you win for every $1 risked if the bet is successful.
  3. Calculate Expected Value (EV). Calculated by comparing our True Probability versus the Payout Odds. The result tells us the expected Return on Investment (ROI) for every $1 wager.
  
  We use EV to place money line picks into Value Tiers (for expected ROI) as follows:
  
  ▪  EV > 0.10  - High Value. A significant market error has been detected.
  ▪  0.05 < EV <= 0.10 - Medium Value. A solid, reliable edge.
  ▪  0.00 < EV <= 0.05 - Small Value. A minimal edge, suitable for small stakes.
  ▪  EV <= 0.00 - Lay Off. No long-term expected profit.
  
  The Expected Value (EV) compares your true belief about the outcome with the payout offered by the bookmaker. Any positive result is a value bet.

• 17. HOW DOES YOUR DATA API WORK?

  We offer programmer access to the raw data that we use for our trends through an Application Programming Interface (API). Our flexible API can be used to create your own interesting applications based on the latest NFL game data. For a complete list of the different operations that are available please refer to our API Documentation here.
  
  You can purchase an API access key from our Season Pass page. After purchasing API Access you will be emailed a key that can be used on data requests. The key must be appended to each web request by adding the querystring parameter ApiKey=[YOUR_API_KEY_HERE]. For example, to query a list of all games played in the 2022-2023 season you would make the following web request:
  
  https://www.spreadtrends.com/api/nfl/games/2022?ApiKey=[YOUR_API_KEY_HERE]
  
  If you do not have a valid API Key on your request you will be redirected to the Login page.
  
  All NFL game stats are updated by Tuesday at 6pm EDT.

• 18. WHAT ELSE SHOULD I KNOW ABOUT YOUR SITE?

  Here are a few noteworthy items about our data, display, and calculations:
  
  Spreads & Records
  
  ▪  All point spreads and totals on the website are closing lines. The lines used are from a sampling of sportsbooks.
  ▪  Unless "straight up" (SU) is explicitly labeled you can assume the trend or result is against the spread (ATS).
  ▪  Home records include games where the team was the designated home team on a neutral field.
  ▪  Post MNF and post Bye week game records only include games from the regular season, postseason play is not included.
  ▪  Conference records exclude divisional games for a clean look at team performs against the rest of the conference.
  
  Stats & Calculations
  
  ▪  Offensive yards gained or allowed do not include yards gained or allowed on special teams in our calculations.
  ▪  Fumbles (Fum) and fumbles lost (Lost) on team pages are total fumbles by the team, not just rusher fumbles.
  ▪  The OU "Inclement Weather" category includes games played outdoors in rain, snow, or wind.
  
  Rankings & Color Coding
  
  ▪  Win percentages are color coded into > 55% (green), < 50% (red) and between 50% and 55% (black) on all pages.
  ▪  Spread strategy margins are color coded into > 1.5 (green), < 1.0 (red) and between 1.0 and 1.5 (black).
  ▪  Rankings are color coded into the top ten (green), bottom ten (red) and middle (black).