Putting text in Circle as big as possible

It´s a pretty basic problem but I couldn´t find a proper solution for it. I have several circles which have text in it like you can see in the picture. The text gets loaded dynamically and has a size from one word up to five words or more. The goal is to put the text as big as possible into the circle. New lines can appear but every individual word should stay together. The example image is kind of ok but I would prefer the text to be bigger because there is still some free space between the text and the circle. The circle is 80x80. All solution I tried cropped the text strangly or the text is too small.

How I create the label:

UILabel *buttonlabel = [[UILabel alloc] initWithFrame:CGRectMake(12,7,57,64)];

    [buttonlabel setText: @"Text"];
    buttonlabel.font = [UIFont fontWithName:@"HelveticaNeue-Light" size:18.0f];
    buttonlabel.textColor = [UIColor whiteColor];
    buttonlabel.textAlignment = NSTextAlignmentCenter;
    buttonlabel.lineBreakMode = NSLineBreakByWordWrapping;
    buttonlabel.numberOfLines = 3;
   [button addSubview:buttonlabel];
   [buttonlabel release];