Both sides of the coin…
The ‘true’, ‘fair’ or ‘zero’ odds are all synonyms for those odds which exactly reflect the statistical expectation of an event. For example, the ‘true’ odds for the toss of a coin are 2.0 (evens), because the probability of the coin landing heads or tails is exactly 50/50.
Odds calculation in football matches is unfortunately not as straight forward as the coin toss. However, it is sufficient to have a relatively basic understanding of numbers in order to compute football odds. Calculations depend entirely upon the size of the data set for each match and the most accurate predictions usually derive from games where there is plenty of historical data available for analysis.
This article explains the odds computations for matches such as cup finals or games within international tournaments where the venues are invariably neutral. For a team to have reached a cup final or major international tournament, it is rare that they then have insufficient historical statistics available to analyse and judge.
The important initial point to make is that only the away statistics in such games are used as the match is effectively an away game for both teams.
Exactly which data go into the formulae?
- Results of the last 25 away matches of the respective teams (all competitions, excluding ‘friendlies’)
- Head-to-head statistics of all games at all venues from the last 10-12 years or a minimum 25 of the most recent encounters
The real-game example we shall use in this article is the DFB-Pokalfinale (German Cup final) between Borussia Dortmund and Bayern Munich played on 12th May, 2012, in Berlin.
1. Historical raw data
This involves nothing more than a simple counting exercise:
Head-to-head (Dortmund v. Bayern, 28 matches since 1998, all competitions, all venues):
- Dortmund eight wins (28.6%); eight draws (28.6%); Bayern 12 wins (42.8%)
Dortmund’s last 25 away matches (all competitions):
- Dortmund 13 wins (52%); seven draws (28%); five defeats (20%)
Bayern’s last 25 away matches (all competitions):
- Bayern 12 wins (48%); five draws (20%); eight defeats (32%)
2. Computation of odds
If the head-to-head data satisfy our quantity requirements then the probability expectations are calculated using exactly 50/50 weighting between the head-to-head results and the current form (the last away 25 matches).
Computation of the odds for Dortmund:
- 32% Bayern away defeats plus 52% Dortmund away wins = 84%
- 84% divided by 2 = 42% (→ average A)
- 42% plus 28.6% Dortmund wins (head-to-head) = 70.6%
- 70.6% divided by 2 = 35.3% (→ average B = Dortmund win probability)
Computation of the odds for Bayern:
- 20% Dortmund away defeats plus 48% Bayern away wins = 68%
- 68% divided by 2 = 34% (→ average A)
- 34% plus 42.8% Bayern wins (head-to-head) = 76.8%
- 76.8% divided by 2 = 38.4% (→ average B = Bayern win probability)
Computation of the DRAW odds:
- 100% minus 35.3% (Dortmund win probability) minus 38.4% (Bayern win probability) = 26.3%