Monthly Child Support Calculator. This calculator provides an estimate for a single source of income.Can a Texas resident get California rate child support if the children have lived in texas for over 5 years? Learn all about child support in California, including how support amounts are calculated, how to change existing child support, and more. These forms allow parents, families, and employers to provide the Child Support Division with additional information so we can better serve you. Texas calculates child support based on the gross income of the paying parent. States generally use one of three models to determine the base child support amount due. Explanations of each model and the states that use them follow. Either parent, or a legal guardian, can enroll in services whether or not a child support court order exists. Child support in California can be confusing.