American odds betting: Guide and Key Rules
This article explains how American odds work, how to calculate payouts and implied probability, and the common settlement rules bettors should know. Use this as a general reference—bookmaker terms, market rules, and jurisdictional regulations vary, so always check the operator’s published rules before placing a bet.
What are American odds?
American odds (also called moneyline odds) show how much you would win relative to a fixed stake and indicate whether a selection is the favorite or underdog.
Positive odds (e.g., +150) show how much profit you would make on a $100 stake. +150 means a $100 stake wins $150 profit, returning $250 total.
Negative odds (e.g., -150) show how much you must stake to win $100. -150 means you must stake $150 to win $100 profit, returning $250 total.
How to convert and calculate payouts
Two useful conversions are to decimal odds (for quick payout math) and to implied probability (an estimate of the market’s chance of the outcome).
Convert to decimal odds
If odds are positive: decimal = (American / 100) + 1. Example: +150 → (150/100) + 1 = 2.5.
If odds are negative: decimal = (100 / |American|) + 1. Example: -150 → (100/150) + 1 ≈ 1.6667.
Calculate implied probability
For positive odds: probability = 100 / (American + 100). Example: +150 → 100 / (150 + 100) = 0.40 → 40%.
For negative odds: probability = |American| / (|American| + 100). Example: -150 → 150 / (150 + 100) = 0.60 → 60%.
Compute payout — use decimal odds: total return = stake × decimal. Profit = total return − stake.
Example 1: Stake $100 on +150 (decimal 2.5) → return $250, profit $150.
Example 2: Stake $100 on -150 (decimal ≈1.6667) → return ≈$166.67, profit ≈$66.67.
Stake needed to win a target amount
For positive odds (+A): stake = target / (A / 100). Example: to win $200 on +150, stake = 200 / (150/100) ≈ $133.33.
For negative odds (−A): stake = target × (A / 100). Example: to win $200 on −150, stake = 200 × (150/100) = $300.
Key rules and settlement conditions
Acceptance time locks the odds: The odds on your ticket are those accepted at the time the bookmaker confirms your bet. Odds displayed later do not change accepted bets.
Event must meet settlement criteria: Bets generally settle according to whether the event starts, completes, or reaches a minimum completion threshold (this varies by sport and operator). Postponed or abandoned events can be voided depending on the operator rules and timing.
Pushes and voids: If the result is a push (e.g., a point spread lands exactly on the handicap) most operators return the stake. In parlays, a pushed leg is usually removed and the parlay pays at the reduced number of legs; policies can differ, so check terms.
Dead heats and ties: In events where multiple selections cross the finish line together (common in horse racing), stake and payout may be adjusted pro rata under dead-heat rules. Exact handling varies by market and provider.
In-play / live bets: Live markets settle on the outcome at the time the market is closed or when the official result is recorded. Suspensions, technical errors, or abandoned contests may lead to voids or special settlement rules based on the operator and the governing sporting body.
Market limits and acceptance: Bets can be rejected, limited, or voided if placed after official suspension, due to exceeding liability limits, or when markets are mispriced. Operators maintain the right to refuse or void bets under specified conditions.
Practical examples
Single bet: You stake $50 on +200. Decimal = 3.0 so return = 50 × 3.0 = $150. Profit = $100.
Parlay: Two-leg parlay with +150 (decimal 2.5) and −120 (decimal ≈1.8333). Parlay decimal = 2.5 × 1.8333 ≈ 4.5833. A $10 stake returns ≈ $45.83 total.
Responsible gambling and fair expectations
Sport betting is a form of entertainment and carries financial risk. Do not treat betting as a way to guarantee income. Set limits, manage bankroll, and use tools offered by operators (deposit limits, time-outs, self-exclusion) if you need them. If gambling causes harm, seek help from local support services and responsible gambling organizations in your jurisdiction.
Short FAQ
Q: What does +100 mean? A: +100 is even money—stake $100 to win $100 (decimal 2.0), implied probability 50%.
Q: Can odds change after I place a bet? A: No — once your bet is accepted, the accepted odds are fixed for that ticket. Displayed odds for the same market may change for new bets.
Q: What happens if a match is postponed? A: Settlement depends on the operator’s rules and the event’s new timing. Some markets require completion within a set time window; others void bets if not played within that window. Always check the market terms.
Q: Do implied probabilities add up to 100%? A: No. The sum of implied probabilities across all outcomes typically exceeds 100% because the bookmaker’s margin (vig) is included.
For specific settlement rules or dispute resolution, consult the terms and conditions of the bookmaker you use and the regulatory framework in your jurisdiction.