Odds Converter
Odds Converter
Choose whether you're converting a probability into odds, or odds into a probability, then enter the corresponding values. This calculates the probability percentage, the simplified odds ratio, and the decimal odds format used by bookmakers.
Probability and odds describe the same likelihood in two different languages, and sports betting, horse racing, and casual wagering tend to use odds while statistics and everyday reasoning tend to use probability — this calculator translates cleanly between them. Odds "for" an event are expressed as favorable-to-unfavorable outcomes (simplified to lowest terms), while decimal odds — the format most common with European bookmakers — equal 1 divided by the probability, representing the total payout multiplier per unit staked.
- Probability to odds: odds for = favorable : unfavorable, simplified to lowest whole-number terms using the greatest common divisor.
- Decimal odds: equal to 1 ÷ probability — this is the total payout multiplier per unit staked, the format most commonly used by European bookmakers.
- Odds to probability: probability = odds-for ÷ (odds-for + odds-against), converting a ratio back into a percentage chance.
What's the difference between "odds for" and decimal odds?
"Odds for" (like 1:3) expresses favorable-to-unfavorable outcomes as a ratio, while decimal odds (like 4.0) express the total return per unit staked, including your original stake — they describe the same underlying probability differently.
Why are the odds ratio numbers sometimes not simplified as I expect?
The ratio is always reduced to its simplest whole-number form using the greatest common divisor of both sides, so a ratio like 50:50 always shows as 1:1.
Choose whether you're converting a probability into odds, or odds into a probability, then enter the corresponding values. This calculates the probability percentage, the simplified odds ratio, and the decimal odds format used by bookmakers.
Probability and odds describe the same likelihood in two different languages, and sports betting, horse racing, and casual wagering tend to use odds while statistics and everyday reasoning tend to use probability — this calculator translates cleanly between them. Odds "for" an event are expressed as favorable-to-unfavorable outcomes (simplified to lowest terms), while decimal odds — the format most common with European bookmakers — equal 1 divided by the probability, representing the total payout multiplier per unit staked.
- Probability to odds: odds for = favorable : unfavorable, simplified to lowest whole-number terms using the greatest common divisor.
- Decimal odds: equal to 1 ÷ probability — this is the total payout multiplier per unit staked, the format most commonly used by European bookmakers.
- Odds to probability: probability = odds-for ÷ (odds-for + odds-against), converting a ratio back into a percentage chance.
What's the difference between "odds for" and decimal odds?
"Odds for" (like 1:3) expresses favorable-to-unfavorable outcomes as a ratio, while decimal odds (like 4.0) express the total return per unit staked, including your original stake — they describe the same underlying probability differently.
Why are the odds ratio numbers sometimes not simplified as I expect?
The ratio is always reduced to its simplest whole-number form using the greatest common divisor of both sides, so a ratio like 50:50 always shows as 1:1.