Same Game Parlay Simulator: The Number Your Parlay Calculator Gets Wrong

Every parlay calculator does the same thing: it multiplies your legs. Three 60% legs become a 21.6% parlay, and the calculator tells you that's your chance.

For legs from the same game, that number is wrong, and usually in a way that matters. If a team wins big, its running back probably ran well and the total probably went over. The legs move together. Multiplying them treats them as strangers.

So we built a parlay simulator that doesn't multiply anything. Stokastic plays each NFL game 10,000 times, play by play, and counts how often your whole combo hits in the same game. We showed it off Monday on Falcons at Saints, and every number below comes from that game's pregame sims.

What Multiplying Misses

Multiplied: 28.7%. Counted together: 34.7%.

That's the first three-leg combo the simulator built for a Saints 27-24 game: NO on the Falcons winning by 6+ (68% in the sims, 70¢ on Kalshi, -233), NO on Bijan Robinson 100+ rushing yards (64%, 60¢, -150) and NO on over 54.5 total points (66%, 70¢, -233). Multiply the three sims chances and you get 28.7%. Count the combo inside the same 10,000 games and it hit 34.7% of the time (3,467 sims). That's six percentage points a calculator never sees.

The reason is the story the legs tell together. When Atlanta doesn't run away with it, Bijan usually isn't piling up 100 yards on the ground, and a game without a blowout tends to stay under 54.5. One script, three legs.

A combo on Kalshi gets its own quote, not its legs multiplied, so the card doesn't print a combo price. Tap Check price and the game opens on Kalshi with the live quote. The price beside each leg is that contract's live ask.

Start With a Score

The simulator opens on Pick Your Game Script. Type the final score you expect. The page then looks at the simulated games that finished near that score and builds the combos that fit it, two to six legs, in the markets and price range you pick.

Pick the score before the legs. The legs that make sense in a 27-24 shootout aren't the ones that make sense in a 17-13 slog, and the simulator rebuilds every combo when the score changes.

Three Numbers on Every Card

Sims price is the share of all 10,000 sims where the whole combo hit, written in cents so it lines up with a contract price. 34.7¢ means 34.7% of the time, or +188.

The Kalshi column is each leg's live ask, beside its sims chance. When the side you'd buy costs less than its sims chance, the sims like that leg.

Current script is how often the combo hit in only the games that finished near the score you picked (your pick, not the live score). Here it's 58.2%. That's the price if you're right about the game.

The gap between the sims price and current script is how much the combo leans on your score. A big gap means you're betting the script as much as the legs.

Ask the Sims

Below the combos is a question box. Ask it anything the box score can count, in plain English, and it answers from the same 10,000 games: "How often does Chris Olave score a TD?" came back 49.2% before Monday's game, with Kalshi at 41¢ (+144).

It works the other way too. YES on Bijan Robinson 100+ rushing yards cost 41¢ (+144) on Kalshi, but it hit only 35.9% of the time in the sims, so the answer pointed at NO, the same side the combo above took.

Readers have asked it more than 500 questions since Oct. 1, mostly yardage lines and anytime touchdowns. Ask about a parlay with "and" ("Bijan 100+ rushing yards and the Falcons win") and it counts both together, the same way the cards do.

How I'd Use It

Start with the score you believe, set the legs to three, and look for the combos where the current script number is well above the sims price. That's a combo built on your read. Then check that each leg's Kalshi ask sits below its sims chance, and use Check price for the combo quote before you buy.

The Kalshi Parlay Simulator covers every NFL game Kalshi lists player props on, and the Polymarket Combo Simulator runs the same sims against Polymarket's prices. Both are free. A live mode is next, so you can ask the same questions from the real score during a game.