Kalshi MLB Home Run Edge Board: Sims HR% Vs Market Price

We built this board because home run markets are the cleanest possible test of a projection engine, one hitter, one night, one yes/no question. Kalshi prices that question in cents for dozens of hitters every day. Stokastic's Sims answer the same question from simulated at-bats. We put every listed hitter side by side, rank the disagreements, and grade our own numbers against settlement, every single day.

The Quick Answer

Kalshi's MLB home run contracts pay $1.00 if the named hitter goes deep, and the price in cents reads as the market's probability. The Sims produce their own home run probability for every hitter from thousands of simulated games with tonight's real starters. The full board below ranks every matched hitter by the gap between those two numbers, and the graded record of every past gap sits one link away.

The Full Board

Fetched September 17, 2026 at 3:21 PM ET — 33 Kalshi-listed hitters matched to Sims projections.

For example, the widest gap on the board fetched September 17, 2026 at 3:21 PM ET: Miguel Vargas (CWS vs DET). The Sims put his 1+ home run probability at 10.1%, while the Kalshi book sat at 18c bid / 19c ask, a 18.5c mid that reads as a 18.5% market probability — 8.4 points below the market. That row enters the ledger today and grades itself when the contract resolves Yes or No tonight.

Settlement is mechanical: a 1+ home run contract resolves Yes the moment the hitter's first home run of the game is official, and resolves No when the game ends without one. That is the entire contract, which is why we trust these markets as a grading source for our own simulations.

Reading it: Sims HR% is the simulated probability of at least one home run today. Kalshi Mid is the midpoint of the live bid and ask on the 1+ home run contract, in cents, which reads directly as the market's probability. Gap is Sims minus market, so positive rows are hitters the Sims like more than the price does, and negative rows are hitters the market is paying for more than the simulations support.

The Record

Graded to date: 40 of 155 published HR gaps settled the way the gap pointed. Every graded call lives on the Sims vs Kalshi ledger.

The bar we hold ourselves to: every gap of four points or more that appears on this board gets recorded the day it publishes and graded against Kalshi's settlement, hit or miss. A projection page without a public record is an opinion page. The Sims vs Kalshi ledger is the record.

Why Gaps Exist At All

Prediction markets are good, and most rows on most days show the Sims and the market within a few points of each other, which is mutual confirmation, not a failure of either side. The interesting rows come from the places a simulation engine and an order book work differently. The Sims re-run when lineups confirm, so a late scratch or an unexpected platoon start can move a simulated HR probability before casual money moves the contract. Ballpark and starter handedness are priced into the simulation at the at-bat level, while a market price leans on traders noticing the same thing. And thin books drift: a home run contract that has not traded since morning can sit at a stale price while the Sims moved at lineup lock.

None of that makes the Sims automatically right. The market catches things simulations cannot, injuries whispered before they are announced, a starter tipping pitches, weather shifting an hour before first pitch. That is exactly why the board is graded instead of celebrated: over a season, the record tells you which side of a gap deserved your attention, market by market, in numbers anyone can check.

Use It With The Games Page

The Kalshi MLB picks page runs every day alongside this board with the game-level view: projected team runs against Kalshi's two-sided game prices, plus the day's top five home run gaps in summary. And if the simulated probabilities themselves are what you want, hitter by hitter with projections and ownership, that is the Stokastic MLB Sims, the engine this entire board is built from. New to exchange pricing? Our sister site's Kalshi guide covers contracts, spreads, and settlement in plain language.

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