I wrote a post similar to this a while back, outlining the process for calculating our **first version** of Expected Goals. This is going to be harder. Get out your TI-89 calculators, please. (Or you can just used my **Expected Goals Cheatsheet**).

Expected Goals is founded on the idea that each shot had a certain probability of going in based on some important details about that shot. If we add up all the probabilities of a team’s shots, that gives us its Expected Goals. Our goal is that this metric conveys the quality of opportunities a team earns for itself. For shooters and goal keepers, the details about the shot change a little bit, so pay attention.

The formulas are all based on a logistic regression, which allows us to sort out the influence of each shot’s many details all at once. The formula changes slightly each week because we base the regression on all the data we have, including each week’s new data, but it won’t change by much.

## Expected Goals for a Team

**Start**with -0.19**Subtract**0.95 if the shot was headed (0.0 if it was kicked or othered).**Subtract**0.74 if the shot was taken from a corner kick (by Opta definition)**Subtract**one of the following amounts for the**shot’s location**:

**Zone 1**– 0.0

**Zone 2**– 0.93

**Zone 3**– 2.37

**Zone 4**– 2.68

**Zone 5**– 3.55

**Zone 6**– 3.06

Now you have what are called **log odds **of that shot going in. To find the **odds** of that shot going in, put the log odds in an exponent over the number “e”.

**odds**and divide by

**1 + odds**.

### Example: Shot from zone 3, header, taken off a corner kick:

-0.19 – 0.95 – 0.74 – 2.37 = -4.25

e^(-4.25) = .0143

.0143 / (1 + .0143) = 0.014 or a 1.4% chance of going in.

A team that took one of these shots would earn 0.014 expected goals.

## Expected Goals for Shooter

**Start**with -0.28**Subtract**0.83 if the shot was headed (0.0 if it was kicked or othered).**Subtract**0.65 if the shot was taken from a corner kick (by Opta definition).**Add**2.54 if the shot was as a penalty kick.**Add**0.71 if the shot was taken on a fastbreak (by Opta definition).**Add**0.16 if the shot was taken from a set piece (by Opta definition).**Subtract**one of the following amounts for the shot’s location:

- 0.0
- 1.06
- 2.32
- 2.61
- 3.48
- 2.99

Now you have what are called **log odds **of that shot going in. To find the **odds** of that shot going in, put the log odds in an exponent over the number “e”.

**odds**and divide by

**1 + odds**.

### Example: A penalty kick

## Expected Goals for Goalkeeper

**These are calculated only from shots on target.*

**Start**with 1.61**Subtract**0.72 if the shot was headed (0.0 if it was kicked or othered).**Add**1.58 if the shot was as a penalty kick.**Add**0.42 if the shot was taken from a set piece (by Opta definition).**Subtract**one of the following amounts for the shot’s location:

- One) 0.0
- Two) 1.10
- Three) 2.57
- Four) 2.58
- Five) 3.33
- Six) 3.21

**Subtract**1.37 if the shot was taken toward the middle third of the goal (horizontally).**Subtract**0.29 if the shot was taken at the lower half of the goal (vertically).**Add**0.35 if the was taken outside the width of the six-yard box and was directed toward the far post.

Now you have what are called **log odds **of that shot going in. To find the **odds** of that shot going in, put the log odds in an exponent over the number “e”.

**odds**and divide by

**1 + odds**.

### Example: Shot from zone 2, kicked toward lower corner, from the run of play.

e^(0.22) = 1.246

1.246/ (1 + 1.246) = 0.555 or a 55.5% chance of going in.

A keeper that took on one of these shots would gain an additional 0.555 Expected Goals against. If he saved it, then he would be outperforming his Expected Goals by 0.555.

## Frequently Asked Questions

**1. Why a regression model? Why not just subset each shot in a pivot table by its type across all variables?**

**2. Why don’t you include info about penalty kicks in the team model?**

**3. The formula looks quite a bit different for shooters versus for keepers. How is that possible since one is just taking a shot on the other?**

**4. Why don’t you include placement for shooters, then?**