# Total Skill Index

The **Total Skill Index** (or **TSI**) is an official measure of a player's abilities.

Set Pieces and experience do not affect the TSI, but form and stamina are relevant for calculation.

## Meaning

As a general rule, the higher the TSI, the better the player. This is always true for a keeper, however, there are problems with this theory. A player who is average in several skills (*e.g.* inadequate in defending, passing, and scoring, but with excellent stamina) will often have a higher TSI than a more specialized player (*e.g.* excellent defending, but everything else poor or lower). TSI also increases with training and it can also increase and decrease with form. Sometimes, TSI will drop even though form does not. This is an easy way of spotting that a background form change has occurred, and the form sub-level has decreased.

## Formulas

The formula used for the calculation is unknown, but several somewhat successful attempts have been made in approximating the true function.

*The following contents are based on the opinion of Hattrick users — which means that their veracity and accuracy have not been confirmed by any official statement, and consequently they do not necessarily reflect the game reality. Please take this into consideration!*

It is rumoured that HT-Bjorn proclaimed he'll change the TSI calculation formula as soon as someone figures it out.

### Goalkeeper case

Interestingly, goalkeepers typically have higher TSI at the same skill level than outfield players. A common theory is that both form and stamina have a multiplying effect on the TSI, whereas the other skills (for keepers, goaltending only) contribute as a sum of exponential functions.

TSI for goalkeepers is a different matter, since a keeper only specializes in one skill. Goalkeeping sub level can be measured quite accurately based on their TSI and form. For Goalkeepers an approximated formula for TSI calculation is:

`TSIgoalkeeper = [ ( 0.025f + 0.1 ) * [ 10 ( s - 1 ) ] ^(3.4) ] / 100`

with f = Form

and s = Skill (1 = disastrous, 2 = wretched, etc.)

### Outfield players case

For outfield players, the formula for TSI calculation should be as the following one:

`TSI = sqrt(f) * sqrt(st) * ( X * [ PM^3 + DE^3 + SC^3] + Y * WN^3 + Z * PS^3 ) ^2`

f = Form (1 = disastrous, 2 = wretched, etc.)

st = Stamina skill

PM, DE, SC, WN, PS are the skills (Playmaking, Defending,Scoring, Wing, Passing skill)

X, Y, Z are fixed constants (unknown)

## External links

- A very useful TSI Calculator for Hattrick Players can be found in Hattrick TSI Calculator by Chechesa
- Use keeper tool ti calculate skill level.