Convert between betting odds formats
A book shows +150, an article says 5/2, a site displays 3.50 — one number, three dialects, plus the implied probability.
Tools used in this guide
The job
Odds say the same thing in different clothes: American (+150/−200), fractional (3/2), decimal (3.50). Comparing offers or reading foreign coverage means translating between them — and the implied probability underneath all three.
Convert
Type the odds in any format and read all three forms plus the implied win probability. Positive American odds show underdogs; negative show favorites (how much you stake to win 100).
- Fractional 5/2 = decimal 3.50 = American +250: stake 1, profit 2.5, total return 3.5.
- Implied probability for decimal odds is 1 ÷ odds — 3.50 implies ≈ 28.6%.
Worked example
A favorite at −150: that's fractional 2/3, decimal 1.67, implied 60%. The same book's underdog at +130 is 13/10, 2.30, 43.5% — the two probabilities summing past 100% is the bookmaker's margin.
Where it stops
Format conversion and raw implied probability only — it doesn't remove the bookmaker's margin, compare offers, or tell you whether a bet is good value. Even-money formats like Hong Kong or Malay odds are not covered.