21/20 Fractional Odds Explained
- Decimal
- 2.05
- American
- +105
- Fractional
- 21/20
- Implied probability
- 48.78%
- Polymarket
- 49¢
- $100 wins
- 105.00
- American
- +105
- Fractional
- 21/20
- Implied probability
- 48.78%
- Polymarket
- 49¢
- Profit
- 105.00
- Total return
- 205.00
2.050 decimal, +105 American, 48.78% implied probability
Fractional odds of 21/20 pay 105.00 profit on a 100 stake: the top number is the profit, the bottom number the stake. In decimal notation the price is 2.05, in American notation +105, and the implied probability is 48.78%.
What 21/20 pays
Profit is stake multiplied by the fraction; add the stake back for the total return. A 100 stake wins 105.00 and returns 205.00.
| Stake | Profit | Total return |
|---|---|---|
| 10 | 10.50 | 20.50 |
| 25 | 26.25 | 51.25 |
| 50 | 52.50 | 102.50 |
| 100 | 105.00 | 205.00 |
| 500 | 525.00 | 1,025.00 |
| 1,000 | 1,050.00 | 2,050.00 |
Break-even and long-run results
The implied probability of 21/20 is bottom divided by top-plus-bottom, which is 48.78%. Win more often than that and you profit over time.
| Win rate | Return on stake |
|---|---|
| 49% | 0.4% |
| 50% | 2.5% |
| 55% | 12.7% |
| 60% | 23.0% |
| 65% | 33.2% |
21/20 is close to evens with an implied probability of 48.78%. Around evens the fractional ladder is fine-grained (10/11, 20/21, evens, 21/20, 11/10), which is where two-way markets like spreads and totals are usually priced.
Converting 21/20 by hand
Divide the top of the fraction by the bottom and add one for the decimal price, 2.05. For the implied probability, divide the bottom by the sum of top and bottom: 48.78%. American odds follow from the decimal price: odds-against, so (2.05 − 1) × 100 gives +105. The same chance on a prediction market is a 49¢ share.
The vig at 21/20
With both sides of a two-way market at 21/20, implied probabilities would sum to -2.44% above 100%: a -2.50% margin on stakes. The fair price would be 2.00 decimal each side. Try other markets in the devig calculator.
21/20 on a betting exchange
On an exchange 21/20 is worth 2.029 decimal after 2% commission and 1.997 after 5%. Compare with the bookmaker before choosing where to bet.
| Commission | Effective decimal | Effective American | Break-even |
|---|---|---|---|
| 2% | 2.029 | +103 | 49.29% |
| 5% | 1.997 | -100 | 50.06% |
Neighbouring rungs on the ladder
Fractional prices move in fixed rungs rather than smooth steps, so a bookmaker who wants to shorten 21/20 slightly has to jump to the next rung down, and the size of that jump depends on where you are on the ladder. The nearby prices listed below are the rungs on either side of 21/20; each link opens the same set of facts for that price, which is the quickest way to see how much a one-rung move changes the implied probability and the payout.
Same price in other formats
Nearby prices
Nearby prices
Frequently asked questions
What does 21/20 mean in betting?
Fractional odds of 21/20 pay the top number in profit for every bottom number staked. A 100 stake wins 105.00 and returns 205.00. The implied probability is 48.78%.
What is 21/20 in decimal odds?
21/20 is 2.05 in decimal odds: divide the top by the bottom and add 1.
What is 21/20 in American odds?
21/20 converts to +105 in American odds.
Is 21/20 a good price?
A price is good only relative to the true chance. 21/20 implies 48.78%; if you believe the outcome is more likely than that, the price has value. Compare it with a devigged market to check.
Why do bookmakers use a ladder of fractions?
Tradition and readability: prices such as 6/4, 100/30 and 11/10 are quoted instead of their reduced forms because they are what racecourse bookmakers have always used. Decimal odds show the same prices with finer steps.