Frequently asked questions
Short answers. The long ones are on How it works.
What is Delta Sunday?
A free NFL forecasting game. Each week you set a win probability for every game with a slider, and you score points based on how confident you were and whether you were right. You play against other people and against three forecasters: Elo, the betting market, and our blend of the two.
How is it scored?
A rescaled Brier score, the rule FiveThirtyEight's forecasting game used. A game is worth 25 minus the square of your miss divided by 100, where the miss is your percentage against 100 for a win or 0 for a loss. A 100% pick that wins earns 25; a 100% pick that loses costs 75; a 50/50 pick scores zero either way. A 75% pick earns 18.8 if right and costs 31.2 if wrong. Playoff games count double. Ties aren't scored.
What happens if I skip a game?
It counts as a 50/50 pick, so zero points. Elo plays every game, which is how skipping puts you behind it.
What is Elo?
A rating system: every team has a number, and the gap between two teams' numbers converts to a win probability. Winners take points from losers after each game, more for upsets and big margins. We use the version FiveThirtyEight published, with its quarterback adjustment, seeded from their final ratings (released under CC BY 4.0) and replayed forward. Delta Sunday is independent and not affiliated with FiveThirtyEight or ABC News.
What is the market?
The betting consensus: an average of sportsbook moneylines with the bookmaker margin removed, plus the prices on Kalshi and Polymarket. Over 24 seasons the closing market has been the best public forecaster of NFL games.
What is the blend, and what is The System?
The blend weights the market three to one over Elo and nudges toward the favorite when the two agree tightly. The System is the blend turned into a full set of slider rules, ten of them, each tested on 24 seasons of games, including a weather adjustment. Signed-in players get a number for every game and a button that applies them.
Does the site actually beat the market?
Over 1999 to 2022 the blend scored 980 points a season against the market's 977, a hair ahead, and Elo alone 890. That's the honest size of it. The leaderboard scores every forecaster on the same games all season so you can see for yourself.
What are the lock and the bold call?
Two picks frozen before each week's first kickoff. The lock is the game Elo and the market are most sure about together; that rule went 379–71 over 24 seasons, 84%. The bold call is where Elo disagrees most with the market; it went 48%, which is the point of showing it.
Is it free? Do I need an account?
Free. You can read the model numbers and the spots without an account. Signing in, with email and password or an emailed link, unlocks picks, the leaderboard, our two picks of the week, The System, the game plan, pools, and the members' weekly breakdown.
Can I play with friends?
Yes. Create a group on the Groups page and share the invite link. Groups can start counting from any week, so late starters can run a fair race.
What should a beginner do?
Sign in, open The System page, press "apply," and adjust only the games where you know something the models don't. Never go past 90% unless you would bet your week on it. Read How it works when you want the reasons.
Where does the data come from?
Scores and schedules from ESPN. Rest days, closing lines and quarterback box scores from nflverse. FiveThirtyEight's published Elo data (CC BY 4.0) for the starting point and history back to 1920. Moneylines from The Odds API, prices from Kalshi and Polymarket, weather from Open-Meteo.
How often does it update?
It refreshes itself on visits: every 3 minutes on game days, otherwise every 30. Picks lock at kickoff. Model numbers are frozen at kickoff too, so every forecaster is scored on its closing number.
Is this gambling advice?
No. It's a game and a model. The site shows market prices because they're the best forecast available, and it's transparent about where the model is and isn't better than them, which is mostly isn't.
Can I use the numbers elsewhere?
Yes. A public JSON feed of every model's number for the current week is at /api/predictions, updated with the site. Credit Delta Sunday if you publish it.
Is this FiveThirtyEight?
No. FiveThirtyEight closed in 2023 and its name belongs to ABC News; Delta Sunday is independent and not affiliated with or endorsed by either. Their published Elo data and methodology were the starting point, credited and used under the Creative Commons license they chose. Everything since, the markets, the blend, The System, the picks, the backtests, is ours.
How do I get in touch?
Reply to any email the site sends you, the recap or the reminder; those come from a monitored address. We don't publish it on the site because of spam.
Canonical: https://deltasunday.com/faq