California imposes what is called "guideline child support". It is an algebraic formula. Remember your high school algebra? The so-called "variables".
The variables inputted into the formula include:
Number of children.
Percentage of time each child is with each respective parent.
The gross income (or earning ability) of each parent.
Factors which increase net income (such as tax filing status, mortgage interest/property tax deduction) and the factors which might decrease net income (such as health insurance premium).
There are other factors (such as already paying support for a child of another relationship, among others), but those are the basics.
After inputting the relevant factors, the formula yields a product (number). That is the guideline child support.
If it's just math, why do you need an attorney? Because those "other factors" can make a big difference in how much you pay or how much you receive. There is also the issue of bonuses and commissions, self-employed income, tax-free income which all must be considered and argued in a fashion best designed to address the needs of our client.
In addition to guideline child support, there are "mandatory" add-ons: Daycare incurred to allow a parent to work or attend school to obtain employment and special health needs of a child.
Child support continues until a child emancipates. Generally, that means turn age 18, but it can continue to up to age 19 if the child is still attending high school.
To obtain the result best for you, given the circumstances of your case, contact Matthew M. Kremer at www.FamLawCal.com.