Legal Question in Family Law in California

It depends on the incomes of both parents and the timeshare over the children, among other factors. If you want a basic idea of how much you may be required to pay, you can start with the Department of Child Support Services Guideline Calculator.

https://www.cse.ca.gov/ChildSupport/cse/guidelineCalculator

Ms. Bridgford gives a good answer. I would just add that a ballpark figure is 45% of your income after payroll deductions, times the percentage of time they spend with the other parent, minus 45% of the other parent's after-deductions income, times the percentage of time they spend with you. The full calculation is a lot more complicated than that, but that is a rough idea.