PRB stands for Percentage of Rivals Beaten. It answers a simple question about any run: of the horses this one raced against, what percentage did it finish in front of?
The formula
PRB = (field size − finishing position) ÷ (field size − 1) × 100
Worked examples:
- Win a 10-runner race: (10 − 1) ÷ 9 × 100 = 100% — you beat everyone.
- 3rd of 12: (12 − 3) ÷ 11 × 100 = 81.8% — beat 9 of 11 rivals.
- 5th of 6: (6 − 5) ÷ 5 × 100 = 20%.
- Last, or failed to finish: 0%.
Why PRB beats win strike-rate
- It's fair across field sizes. Finishing 4th of 20 (84.2% PRB) is a much better run than 4th of 5 (25%) — raw finishing position treats them the same; PRB doesn't.
- It uses every run, not just wins. Win strike-rate throws away everything below 1st place. A horse running consistent 2nds and 3rds in big fields shows a high average PRB long before it wins — often exactly when it's still a big price.
- It's continuous. Averaging PRB across a trainer's last month, a sire's runners on soft ground, or a jockey's record at a track gives a stable, comparable number where win percentages jump around on small samples.
How RaceMetrics uses PRB
PRB is a foundation of the RaceMetrics rating methodology: our Elo-based ratings update on the gap between a horse's expected PRB (from its rating versus the field's) and its actual PRB. It also powers the Race Workout tool, which averages the subsequent-run PRBs of a race's runners to judge how well the form is working out, and appears as a mode in Form Expert for judging records under today's conditions.
PRB quick reference
| Average PRB | Reading |
|---|---|
| 60%+ | Consistently beating most rivals — genuine ability for the level |
| 50–60% | Better than average; competitive at the level |
| 40–50% | Around average |
| Below 40% | Struggling at the level — needs a drop in class or a change |
FAQ
What does PRB mean in horse racing?
PRB means Percentage of Rivals Beaten — the share of a race's other runners that a horse finished ahead of, calculated as (field size − finishing position) ÷ (field size − 1) × 100.
Is a high PRB good?
Yes. 100% means the horse won; anything consistently above 50% means it beats most of its rivals. Non-finishers score 0%.
Where can I see PRB stats for UK horses?
RaceMetrics shows PRB in its Form Expert view (as a selectable mode alongside win and place), in the Race Workout tool, and throughout its Elo-based rating methodology. There's a free tier to try it.
