How to calculate child support?

Formula child support is a share of the parents' “net monthly disposable income” (Fam.C. § 4055(a) & (b)), computed by totaling “annual gross income” (per Fam.C. § 4058), less allowable deductions to arrive at “annual net” (per Fam.C. § 4059) and then dividing by 12 to yield “monthly net” (per Fam.C. § 4060).

A quick way to check what child support will be is too use the DCSS calculator here: https://www.cse.ca.gov/ChildSupport/cse/guidelineCalculator