How baseball simulation works
A plain-language tour of how the engine turns two rosters into a real, pitch-by-pitch game.
A baseball simulation turns rosters and ratings into games. Simulation Baseball does it the deep way: it plays out every plate appearance, pitch by pitch, and records the result into real box scores, statistics, and standings. Nothing is a coin flip on the final score. The score is what happened across nine innings of modeled baseball.
Every pitch is a decision
On each pitch the engine weighs the matchup in front of it: the batter against this pitcher, the count, the base-out state, the platoon advantage, fatigue, and the situation. It resolves the pitch, then the swing, then the ball in play, and moves the game state forward. Strings of those small outcomes become an at-bat, then an inning, then a game with a real line score and a full box.
Because the engine reasons about the actual matchup rather than rolling against a single “ability” number, the things that matter in real baseball matter here: handedness, a deep bullpen, a tiring starter, a contact hitter who is hard to strike out.
What the engine weighs
A single result is shaped by hundreds of factors working together, among them:
- The batter’s and pitcher’s underlying ratings across contact, power, eye, and stuff, movement, and command.
- Platoon splits and the handedness matchup.
- Fatigue, role, and how deep a pitcher is into his outing.
- The park, the defense behind the pitcher, and the game situation.
No single one of these decides an at-bat. They combine, which is why the same hitter can crush one pitcher and look lost against another.
Every game is reproducible
The simulation is deterministic. Given the same two teams in the same state, it produces the same game every time. That is what makes a result trustworthy: it is not a lucky roll you can refresh away, it is the outcome of the inputs. It is also what lets a shared matchup link replay identically for everyone who opens it.
Where to go next
- How player ratings work covers the numbers behind a player.
- Player development explains how those numbers change over a career.
- Scouting accuracy explains why the numbers you see are an estimate, not the truth.
Run your own front office
These systems power Simulation Baseball, the most advanced browser-based baseball simulation. Free beta, no download.