SANDRACER.COM - Betting Overround

What Does "Betting Overround" Mean?

The Betting Overround(vigorish, juice, vig, overound, over-round) is the name given to the profit margin odds compilers build into a gambling market.

A mathematical formula is used by bookmakers/layers to price up a betting market in the bookies favour, ie the house edge. All odds/prices have an equivalent probability percentage. Evens is 50%, 3/1 is 25%, 9/1 is 10% and so on.

So, when bookies write a book and price up a betting event, they build in a profit margin for themselves by using fractional mathematics. You're not going to get 2 evens shots in a race, otherwise the bookie is actually gambling, just like a punter. Such a market is called a round book.

You may see a 2 horse race, with 2 evenly matched runners, priced up as such (if you are lucky).
Odds of horse 1: 5/6
Odds of horse 2: 5/6

Odds of 5/6 = a 54.55% probability. 54.55+54.55=109.1 This means the bookie should theoretically win 9.1% of the total wagers staked, if the same amount of money has been wagered by punters on each horse.

You can work out the overround, or easily price up your own football match, or even a 40 runner handicap like the Grand National, by writing down the odds percentage and adding up the total. Anything over 100% is the bookies projected profit, all things being equal.

If you find a betting market where the 2 prices add up to less than 100%, that is called arbitrage. Arbitrage means 2 or more layers differ so much on their odds, that you can bet both sides of the event and collect a guaranteed profit, whatever the result.

♠ Overround = Betting market in the layers favour.
♠ Round Book = Betting market in no ones favour.
♠ Arbitrage = Betting market in the punters favour.

UK Odds - Odds%

1/100 = 99.00%
1/50 = 98.03%
1/33 = 97.08%
1/25 = 96.15%
1/20 = 95.23%
1/10 = 90.90%
2/13 = 86.95%
2/11 = 84.74%
1/5 = 83.33%
2/9 = 81.30%
1/4 = 80.00%
2/7 = 77.80%
3/10 = 76.70%
1/3 = 75.00%
4/11 = 73.33%
2/5 = 71.43%
4/9 = 69.23%
1/2 = 66.67%
8/15 = 65.50%
4/7 = 63.64%
8/13 = 61.90%
2/3 = 60.00%
8/11 = 57.89%
4/5 = 55.56%
5/6 = 54.55%
9/10 = 52.63%
10/11 = 52.38%
1/1 = 50.00%
21/20 = 48.78%
11/10 = 47.62%
10/9 = 47.37%
6/5 = 45.45%
5/4 = 44.44%
13/10 = 43.48%
27/20 = 42.55%
11/8 = 42.11%
7/5 = 41.67%
3/2 = 40.00%
8/5 = 38.46%
13/8 = 38.10%
17/10 = 37.04%
7/4 = 36.36%
9/5 = 35.71%
15/8 = 34.78%
19/10 = 34.48%
2/1 = 33.33%
21/10 = 32.26%
11/5 = 31.25%
9/4 = 30.77%
23/10 = 30.30%
12/5 = 29.41%
5/2 = 28.57%
13/5 = 27.78%
27/10 = 27.03%
11/4 = 26.67%
14/5 = 26.32%
3/1 = 25.00%
10/3 = 23.08%
7/2 = 22.22%
4/1 = 20.00%
9/2 = 18.18%
5/1 = 16.67%
11/2 = 15.38%
6/1 = 14.29%
13/2 = 13.33%
7/1 = 12.50%
15/2 = 11.76%
8/1 = 11.11%
17/2 = 10.53%
9/1 = 10.00%
10/1 = 9.09%
11/1 = 8.33%
12/1 = 7.69%
14/1 = 6.67%
16/1 = 5.88%
18/1 = 5.26%
20/1 = 4.76%
22/1 = 4.35%
25/1 = 3.85%
28/1 = 3.45%
33/1 = 2.94%
40/1 = 2.44%
50/1 = 1.96%
66/1 = 1.49%
80/1 = 1.23%
100/1 = 0.99%

♠ Compare Fractional, Decimal, Percentage Probability
♥ Niall O'Connor's Overround Explanation
♠ Vigorish Explained - J R Miller
♠ Vigorish Wiki Information Webpage
♠ What Does Arbitrage Mean - Mike Moffatt
♠ Risk Free Betting Caculator - Darren Hall