Eight years on a licensed sportsbook trading desk — setting lines, watching sharp money move, and learning exactly where recreational bettors lose track of the math — that's the background behind every formula and example on this site. The moneyline bet calculator exists because the arithmetic trips people up constantly, and it shouldn't.
Who built this and why does it matter?
Tim Hadley spent nearly a decade on the trading side before the US sports betting market opened up state by state. He watched bettors place winning picks and still come away confused about what they were owed — or why a -300 favorite returned so little. That gap between knowing the winner and understanding the payout is exactly what this tool closes.
The formulas here follow the standard American odds math used at every licensed US sportsbook, from FanDuel and DraftKings to BetMGM and Caesars. Nothing invented, nothing estimated. If a number appears on this site, it's sourced from the same arithmetic a trading desk would use.
What this site covers
Beyond the calculator itself, the site walks through the mechanics behind the numbers. Want to understand why -110 implies roughly 52.4% probability, or how the vig erodes value on both sides of a line? The hidden cost of vig in moneyline betting guide covers that. Curious why betting -300 favorites feels safe but pays almost nothing? See the breakdown of the heavy-favorite moneyline trap.
There are also guides on implied probability and what your odds are really saying, a deep dive into how American moneyline odds actually work, and a dedicated payout formula page for anyone who wants to run the math by hand. The moneyline calculator FAQ answers the most common questions in plain language.
A note on taxes and legal play
Winning bettors eventually deal with the IRS. All gambling winnings are taxable income, and the 2026 W-2G rule change is worth knowing before year-end. The IRS Topic 419 on gambling income and losses is the primary federal reference.
This site covers legal, licensed US sports betting only — the 29-plus states with active online markets as of 2025. Must be 21+ to wager at most licensed sportsbooks; 18+ in Wyoming and Tennessee. Gambling problem? Call 1-800-GAMBLER.
No calculator tool gives anyone an edge over the house. The math is fixed. Understanding it just means fewer surprises when the payout posts.