Aspect ratio keeping guitexture scaling

I have made a simple script to scale my gui-textures in relation to my screen height and the texture aspect ratio but when I run it it scales my texture in a quadratic shape not in a rectangle. I tried to calculate the values myself and everything was right but somehow the program calculates wrong numbers.

I have read out the start values:

guiTexture.texture.width = 900

guiTexture.texture.height = 600

Screen.height = 879

sizeFactor = 3

the program calculates:

ratio = 1 <-- That is what confuses me :(

tHeight = 293

tWidth = 293

xInset = -146

yInset = -146

I hope you understand my problem and sorry for my bad english :).

Here is my code:

 #pragma strict
 
 var sizeFactor : int;
 
 private var ratio : float;
 private var tHeight : int;
 private var tWidth : int;
 private var xInset : int;
 private var yInset : int;
 
 function Start () {
 
     ratio = guiTexture.texture.width / guiTexture.texture.height;
     tHeight = Screen.height / sizeFactor;
     tWidth = tHeight * ratio;
     xInset = (tWidth / 2) * -1;
     yInset = (tHeight / 2) * -1;
     guiTexture.pixelInset = Rect(xInset,yInset,tWidth,tHeight);
     
     
     transform.position = new Vector3(0.5,0.5,0);
 }
 
 function Update () {
     
     tHeight = Screen.height / sizeFactor;
     tWidth = tHeight * ratio;
     xInset = (tWidth / 2) * -1;
     yInset = (tHeight / 2) * -1;
     guiTexture.pixelInset = Rect(xInset,yInset,tWidth,tHeight);
     
     transform.position = new Vector3(0.5,0.5,0);
 }