American odds – the quick-hit
Positive numbers mean you win that amount on a $100 stake; -150 means you must risk $150 to net $100. Simple, brutal, no fluff.
Decimal odds – the straight-forward multiplier
Take your stake, multiply by the decimal figure, you get total return. 1.75? You profit 0.75 on every dollar. It’s the format you see on most European sites.
Fractional odds – the old-school bookmaker’s chant
Read “5/2” as “for every 2 you risk, you win 5”. It’s a gamble’s poetry, but you must convert to decimal for quick math: (5÷2)+1 = 3.5.
Conversion cheat sheet
American to decimal: if +200, then (200/100)+1 = 3.00; if -250, then (100/250)+1 = 1.40. Decimal to fractional: strip the “1” off, then turn the remainder into a fraction, simplify.
Why the format matters
Because sportsbooks cherry-pick the one that makes their margin look skinny. You, the bettor, need to see the real implied probability. Convert everything to decimal, then flip: 1 ÷ odds = implied %.
Real-world example
Say Tiger is -120 American, 1.83 decimal, 6/5 fractional. Implied probability: 1 ÷ 1.83 ≈ 54.6%. If the book lists him at 52%, you’ve found value.
Common pitfalls
Mixing stake sizes with odds, double-counting the “1” in decimal conversion, or ignoring the bookmaker’s vig. All three will bleed you dry.
Actionable tip
Pick any odds you like, run the formula, compare the implied % to your own model, and bet only when yours is higher. https://betting-on-golf.com/articles/how-golf-betting-odds-work-american-decimal-and-fractional-formats-explained/