The amount depends on the child’s needs and the parents’ ability to pay.
As already explained, the parent with whom the child lives provides maintenance in kind. The other parent pays monetary maintenance (alimony).
Basically, the higher the income, the higher the alimony. Also, the older the child, the higher the alimony. Jurisprudence in Austria has developed the so-called percentage value method for calculation. While 16% of the monthly net income is to be paid in alimony for children between 0 and 6 years of age, this gradually increases to 22% for children over 15 years of age. If the person liable for alimony has further maintenance obligations (further children or towards a (divorced) spouse), there are deductions.
In any case, the decision on the amount of monetary maintenance is always made on a case-by-case basis by the respective competent court.