Horse racing Win: devig calculator
- Market
- 6-way
- Typical overround
- 10%–25%
- Sample overround
- 5.95%
- Worst-case probabilities are per-outcome minimums and do not add up to 100%.
| Outcome | Multiplicative | Additive | Powerk = 1.037 | Shinz = 0.012 | Worst case |
|---|---|---|---|---|---|
| Outcome 1 | 31.46%3.179 | 32.34%3.092 | 32.01%3.124 | 31.98%3.127 | 31.46%3.179 |
| Outcome 2 | 23.60%4.238 | 24.01%4.165 | 23.76%4.209 | 23.83%4.196 | 23.60%4.238 |
| Outcome 3 | 18.88%5.298 | 19.01%5.261 | 18.85%5.305 | 18.95%5.277 | 18.85%5.305 |
| Outcome 4 | 13.48%7.417 | 13.29%7.522 | 13.30%7.520 | 13.37%7.481 | 13.29%7.522 |
| Outcome 5 | 7.87%12.714 | 7.34%13.622 | 7.61%13.149 | 7.56%13.230 | 7.34%13.622 |
| Outcome 6 | 4.72%21.190 | 4.01%24.950 | 4.48%22.331 | 4.32%23.171 | 4.01%24.950 |
- Overround
- 5.95%
- Margin
- 5.62%
- Outcomes
- 6
Overround 5.95%
Win markets in horse racing have overrounds that grow with the number of runners. Non-runners trigger deductions under Rule 4, which change every remaining price after the fact and can undo an arbitrage.
Overround in this market
Horse racing Win has 6 outcomes (
Runner 1, Runner 2, Runner 3, Runner 4, Runner 5, Runner 6). Bookmakers usually price it with an overround between 10% and 25%. Sharper books sit at the low end; recreational books and multi-way fields at the high end.
Worked example
Sample prices of 3.00 / 4.00 / 5.00 / 7.00 / 12.00 / 20.00 carry an overround of 5.95% (margin 5.62%). Multiplicative devigging gives fair probabilities of 31.5% / 23.6% / 18.9% / 13.5% / 7.9% / 4.7% and fair odds of 3.18 / 4.24 / 5.30 / 7.42 / 12.71 / 21.19. The calculator above starts from these prices and shows every method side by side.
| Outcome | Odds | Implied | Fair probability | Fair odds |
|---|---|---|---|---|
| Runner 1 | 3.00 | 33.3% | 31.5% | 3.18 |
| Runner 2 | 4.00 | 25.0% | 23.6% | 4.24 |
| Runner 3 | 5.00 | 20.0% | 18.9% | 5.30 |
| Runner 4 | 7.00 | 14.3% | 13.5% | 7.42 |
| Runner 5 | 12.00 | 8.3% | 7.9% | 12.71 |
| Runner 6 | 20.00 | 5.0% | 4.7% | 21.19 |
Multi-way markets and method choice
The larger the field, the more the methods disagree. Multiplicative devigging spreads the margin evenly and overrates the favourites' fair chance; power and Shin move more of the margin onto the outsiders, which matches how bookmakers actually price them. Compare all five before pricing a longshot.
Frequently asked questions
What is a normal overround for Horse racing Win?
Between 10% and 25% at most bookmakers. Lower means a sharper book; multi-way fields run higher.
Which devig method should I use for Horse racing Win?
With 6 outcomes priced close together the methods agree. When one outcome is a heavy favourite or the field is large, power or Shin better model where the margin sits; worst case gives the most conservative probability.
What are the fair odds for the sample prices?
The sample prices 3.00 / 4.00 / 5.00 / 7.00 / 12.00 / 20.00 carry an overround of 5.95%. Multiplicative devigging gives fair probabilities of 31.5% / 23.6% / 18.9% / 13.5% / 7.9% / 4.7% and fair odds of 3.18 / 4.24 / 5.30 / 7.42 / 12.71 / 21.19.
Can I use the fair probability to size a bet?
Yes: enter it with an offered price in the EV & Kelly calculator, or use the devig calculator's price-check panel, which reports edge and Kelly stake for each method.