# how to Calculate Vigorish on Bookies Odds.

**URL:** <https://boards.straightdope.com/t/how-to-calculate-vigorish-on-bookies-odds/617626>\
**Category:** Factual Questions\
**Created:** [April 2, 2012, 8:18pm UTC](https://boards.straightdope.com/t/how-to-calculate-vigorish-on-bookies-odds/617626 "2012-04-02T20:18:01Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![notfrommensa](https://avatars.discourse-cdn.com/v4/letter/n/f14d63/32.png) [@notfrommensa](https://boards.straightdope.com/u/notfrommensa)\
**Post date:** [April 2, 2012, 8:18pm UTC](https://boards.straightdope.com/t/how-to-calculate-vigorish-on-bookies-odds/617626/1 "2012-04-02T20:18:01Z")

</div>

(this is how-to question, that is why I posted in GQ, but I can see merit for it going to Game Room)

I have been looking at the odds for the Masters Golf Tournament, and I wondering if I am calculating the “Vig” correctly.

Ladbrokes, an online and brick/mortar bookie in the UK, [Masters Odds](http://sports.ladbrokes.com/en-gb/Golf-c110000008) .

Current odds for the five favorites

Tiger is 9/2  
McIlroy is 6/1  
Mickelson is 12/1  
Donald is 16/1  
Westwood 20/1

and it goes to 5000/1 for Ben Crenshaw.

I calculate the Vig as the sum of the reciprocal of the odds for each player in the field minus 1.

```auto

Vig =(∑ **1 / (odds)**) - 1

```

In this case, the sigma part of the formula adds up to be 1.36, which leads me to conclude the VIG is 0.36 or 36%. which seems to be really high. (of course I realize that they are in business to make money)

Is the formula that simple, or am I missing something obvious?

---

<div class="post-metadata">

**Author:** ![Freddy\_the\_Pig](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@Freddy\_the\_Pig](https://boards.straightdope.com/u/Freddy_the_Pig)\
**Post date:** [April 2, 2012, 9:09pm UTC](https://boards.straightdope.com/t/how-to-calculate-vigorish-on-bookies-odds/617626/2 "2012-04-02T21:09:27Z")

</div>

A couple of adjustments–first, sum the reciprocals of the odds + 1. In other words Tiger is 4.5 to 1 so sum 1/5.5, not 1/4.5. Your new sigma is 1.275.

Then the vig = (sigma - 1) / sigma, or .275/1.275 = 21.6%.

---

<div class="post-metadata">

**Author:** ![notfrommensa](https://avatars.discourse-cdn.com/v4/letter/n/f14d63/32.png) [@notfrommensa](https://boards.straightdope.com/u/notfrommensa)\
**Post date:** [April 2, 2012, 9:54pm UTC](https://boards.straightdope.com/t/how-to-calculate-vigorish-on-bookies-odds/617626/3 "2012-04-02T21:54:17Z")

</div>

I thought about your first adjustment but never would have thought about dividing it by the sigma.

Thanks