In California, child support is calculated using a specific formula. The state provides a California Child Support Guideline Calculator, which offers a general estimate of how much child support will be in your case. It should be noted, however, that the court can order a different amount based on the unique circumstances of your case. The formula that a California judge will utilize to calculate child support takes into account both parents' income, the respective percentage of time that the parents spend with their child, and the number of children.