Odds converter
Enter a price in any format and get the other three, plus the implied probability and the return on a $100 stake. Free, no account, and it runs in your browser.
The Australian standard. 4.00 returns $4.00 for every $1 staked, stake included.
- Decimal
- 4.00
- Fractional
- 3/1
- American
- +300
- Implied probability
- 25.00%
- Returns on a $100 stakestake included
- $400.00
The four formats
Decimal. The Australian standard, and the format the Betfair exchange uses. It shows the total return per dollar staked, stake included, so 4.00 returns $4.00 on a $1 bet.
Fractional. The traditional British format, written as profit to stake. 3/1 means three dollars of profit for every one staked, which is decimal 4.00. Odds shorter than even money invert the fraction: 10/11 is decimal 1.91.
American. Also called moneyline. A positive number is the profit on a $100 stake, so +300 is decimal 4.00. A negative number is the stake needed to win $100, so -200 is decimal 1.50. Even money sits at exactly +100.
Implied probability. One divided by the decimal odds, expressed as a percentage. It is the format worth thinking in, because it turns a price into a statement about how likely the market thinks something is.
The formulas, in plain language
Decimal to fractional
fraction = decimal odds - 1, written as a fraction
Decimal to American
if decimal is 2.00 or longer: (decimal - 1) x 100
if decimal is shorter than 2.00: -100 / (decimal - 1)
Decimal to implied probability
implied probability = (1 / decimal odds) x 100
Back the other way
fractional to decimal: (numerator / denominator) + 1
positive American to decimal: (american / 100) + 1
negative American to decimal: (100 / |american|) + 1
probability to decimal: 100 / probability
Common conversions
| Decimal | Fractional | American | Implied probability |
|---|---|---|---|
| 1.25 | 1/4 | -400 | 80.00% |
| 1.50 | 1/2 | -200 | 66.67% |
| 1.91 | 10/11 | -110 | 52.36% |
| 2.00 | 1/1 | +100 | 50.00% |
| 2.50 | 3/2 | +150 | 40.00% |
| 3.00 | 2/1 | +200 | 33.33% |
| 4.00 | 3/1 | +300 | 25.00% |
| 6.00 | 5/1 | +500 | 16.67% |
| 11.00 | 10/1 | +1000 | 9.09% |
| 21.00 | 20/1 | +2000 | 4.76% |
Decimal 1.91 and its American equivalent of -110 are the prices you will see quoted most often on two-way sports markets. Both sides priced at 1.91 add up to 104.7 percent, and that 4.7 percent is the operator's margin.
Why this matters when you are covering a bet
Australian bookmakers quote decimal odds and so does the exchange, but promotion terms, overseas sources and betting content are often written in fractional or American. Converting in your head is where mistakes start, and an odds mistake feeds straight into a wrong lay stake. If you are working out the lay side of an offer, the matched betting calculator takes decimal odds on both legs.
Other calculators
- Matched betting calculator: back and lay, with commission.
- Bonus bet calculator: turn a bonus bet into cash.
- Dutching calculator: split a stake across outcomes.
- All free calculators: the full list with an explanation of each one.
Frequently asked questions
What are decimal odds?
Decimal odds show the total return for every dollar staked, including the stake itself. Odds of 4.00 return $4.00 for a $1 stake: $3.00 profit plus the $1 back. They are the standard format used by Australian bookmakers and by the Betfair exchange.
How do you convert decimal odds to fractional?
Subtract one from the decimal odds and express the result as a fraction. Decimal 4.00 becomes 3.00, which is 3/1. Decimal 2.50 becomes 1.50, which is 3/2. Fractional odds describe profit relative to stake, which is why the stake portion comes out first.
How do you convert decimal odds to American odds?
Decimal 2.00 is the pivot. At or above it, the American price is the decimal odds minus one, multiplied by 100, written with a plus sign: 4.00 becomes +300. Below it, the American price is minus 100 divided by the decimal odds minus one: 1.50 becomes -200.
What is implied probability?
The chance of an outcome that a price implies, calculated as one divided by the decimal odds. Odds of 4.00 imply 25 percent. It is the most useful format for comparing two prices, and for spotting the bookmaker margin when the implied probabilities of a market add to more than 100 percent.
Why do the implied probabilities of a market add up to more than 100 percent?
That excess is the bookmaker's margin, sometimes called the overround. A fair two-way market would price both sides at 2.00, totalling exactly 100 percent. Anything above that is the operator's edge, which is why comparing prices across bookmakers matters.
Why does the fractional result sometimes say nearest standard fraction?
Because not every decimal price has a tidy fractional equivalent. Decimal 4.33 is 3.33 to one, which is closest to the standard fraction 10/3 rather than an exact match. The converter shows the nearest common fraction and labels it, rather than quoting something like 333/100.
Written by the YAUPICKS team. Last reviewed July 2026.
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