Step into any betting shop or open a sports wagering app. Numbers everywhere. Minus signs, fractions, decimals-all screaming for attention. The confusion hits fast.
But here’s something interesting: these formats exist because different regions developed their own mathematical languages. Three major kinds of odds dominate the world’s markets-American, decimal, and fractional-each representing the same information in various ways. Americans built their system around $100 benchmarks. Europeans chose decimals for quick multiplication. The British stuck with fractions dating back centuries to horse racing traditions. Platforms like Onjabet Iran typically allow users to switch between these formats in their settings, letting bettors work with whichever style feels most natural to them.
None is inherently better. They are all translators of probability into potential profit. Once you break the code, moving between the different formats becomes instinctive.
Decoding American odds: the plus and minus system
American odds use plus and minus signs to separate favorites from underdogs, with the calculations anchored to $100 baselines. The minus tells you what to risk. The plus reveals what you’ll win.
See -150? You’re putting up $150 to collect $100 profit. Spot +200? Your $100 bet returns $200 profit. All positive and negative lines return your original stake on top of any winnings. That $150 bet at -150 pays back $250 total ($100 profit plus the $150 you risked).
Breaking down common scenarios:
- Negative odds indicate favorite status and the amount risked for every $100 won.
- Positive odds indicate underdog position and profit on $100 stake
- Standard spreads usually have -110 on both sides.
- Heavy favorites can reach -500 or beyond.
- Long shots might show +2000 or higher
The scale is proportional, meaning betting $15 at -150 yields a profit of $10. Betting $10 at +200 yields $20 profit. Math remains the same regardless of size.
Break-even calculations are important: standard -110 lines require return bets of 52.38% over time to just break even. That additional 2.38% beyond the coin-flip represents the house edge, otherwise known as vigorish or juice. Understanding this margin is what separates casual bettors from informed ones.
Decimal odds: European clarity
Decimal formats show the total potential returns including the original stake, which makes them the easiest for quick calculations: multiply your stake by the decimal. Done.
Bet £50 at 3.20 and get back a total of £160. Your profit? Subtract the original £50 to get £110. Decimals above 2.0 signal underdogs while numbers below 2.0 indicate favorites. The 2.0 threshold represents even money-double your stake if you win.
Most modern betting interfaces allow format switching. A bettor might see 2.50 displayed as decimal, 3/2 as fractional or +150 in American format-all representing identical value. The math connects through simple conversion formulas, but the decimal system eliminates extra steps.
Fractional odds: British heritage
Fractional odds reflect the potential profit in relationship to stake using ratios like 5/1 or 2/7. The left number expresses what you win. The right reflects what you wager.
At 7/2, every £2 staked returns £7 profit plus your £2 back. So, a £20 bet produces a profit of £70 (£20 divided by 2, multiplied by 7), plus the £20 returning, equals a payout of £90. Horse racing still uses this format predominantly, maintaining tradition over convenience.
Odds-on selections flip the fraction. At 1/4 odds, you’re betting £4 to win just £1 profit-a heavily favored outcome. These short prices reflect high probability events where bookmakers expect the favorite to win most encounters.
Converting between formats
The three systems are interconnected through mathematical relationships. To convert American odds into decimal, there are two approaches: for positive odds, divide by 100 and then add 1; for negative odds, divide 100 by the absolute value, then add 1.
American +200 becomes 3.00 decimal, or 200÷100 + 1. American -150 converts to 1.67, or 100÷150 + 1. Fractional odds convert by adding 1 to the decimal equivalent of the fraction. Thus 5/2 equals 2.5, which becomes 3.5 in decimal format.
These are very important conversions when comparing markets across different betting sites. A sharp bettor compares a number of sources, converting everything to their preferred format, then identifying the best available price.
Implied probability and finding value
Implied probability is a calculation of the percentage chance that odds suggest an outcome will happen. This number shows if bookmakers have appropriately priced markets.
To convert this into an implied probability, we take 100/(120+100) = 45.45% for American odds of +120. For American odds of -120, we perform the calculation of 120/(120+100) to get 54.55%. We convert decimal odds by dividing -1 by the decimal and then multiplying by 100.
But here’s where it gets interesting. If your research suggests that a team has 60 percent actual win probability, but odds imply only 50 percent, value exists. That 10-point gap represents long-term potential profit. In finding these discrepancies, you have to compare personal probability assessments against market prices.
