American Odds (Moneyline) Explained

What are American odds (moneyline odds)?

American odds (often called moneyline odds) are the + / − numbers you see at sportsbooks: -110, +150, -200, etc. They describe both:

• How much you win if you’re right (profit), and
• How often you must win to break even (implied probability).

Negative odds (favorites): what “-” means

Negative odds look like -110, -150, -200. They imply the outcome is more likely, so the payout is smaller.

Payout math (negative odds)

• Profit if win: profit = stake × (100 / A) where A = abs(odds)
• Total return: stake + profit

Examples

• -110 with $100 stake → profit ≈ $90.91
• -200 with $100 stake → profit = $50.00

Positive odds (underdogs): what “+” means

Positive odds look like +120, +150, +250. They imply the outcome is less likely, so the payout is larger.

Payout math (positive odds)

• Profit if win: profit = stake × (A / 100) where A = odds
• Total return: stake + profit

Examples

• +150 with $100 stake → profit = $150.00
• +250 with $100 stake → profit = $250.00

Implied probability (break-even) from American odds

Implied probability is the win rate you need to break even at that price. It’s not a prediction—it’s the odds translated into a percentage.

Break-even formulas

• Positive odds (+A): implied = 100 / (A + 100)
• Negative odds (-A): implied = A / (A + 100) where A = abs(odds)

Break-even examples

• +150 → 100/250 = 40.00%
• -110 → 110/210 ≈ 52.38%
• -200 → 200/300 ≈ 66.67%

Why sportsbooks show odds, not win percentage

• Odds are the pricing format; the “%” is just a conversion.
• The implied % includes the book’s margin (vig), especially in two-sided markets.
• Your “true” win % is a separate estimate (model, matchup analysis, market comparison).

How this connects to EV

Once you have odds (payout) and a win probability estimate, EV is straightforward:

• EV = p(win) × profit − (1 − p(win)) × stake

That’s why BettorCalc lets you enter a probability: EV depends on what you believe the true win rate is.

Practical tips

• Line shop: small changes in odds change break-even and long-run results.
• Use break-even as baseline: if you don’t have a probability model, start here.
• Don’t confuse implied % with truth: it’s a price conversion, not a forecast.