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California sets guideline child support with a single statewide formula in Family Code §4055: CS = K[HN − (H%)(TN)], where TN is the parents' combined net disposable income, HN is the higher earner's net income, H% is the higher earner's share of parenting time, and K is a factor that scales with income and the number of children. This calculator applies that formula to the net figures you enter and shows each step, including the K factor and any multi-child multiplier.
The single biggest driver is net disposable income — income after taxes and the §4059 deductions — not gross pay. Parenting time is the second: because the formula subtracts the higher earner's timeshare, more parenting time for the higher earner lowers the guideline amount. The 2024 update (SB 343) refined how the formula treats low earners and larger families.
California's official guideline calculators are certified by the Judicial Council and compute net disposable income from gross pay and taxes. Our tool takes the net figures directly so you can reproduce the math and understand it; for a court-ready figure, confirm on a certified calculator. This is a preparation estimate, not legal advice.
Each parent's net disposable income — gross income minus taxes and the §4059 deductions such as mandatory retirement, health premiums, union dues, and support paid for other relationships. Entering gross pay overstates support; our tool can start from net directly.
The §4055 formula subtracts the higher earner's share of parenting time (H%), so the more time the higher earner has, the lower the guideline transfer. Adjust the timeshare slider to see the effect.
K is a statutory multiplier in the §4055 formula that scales with the parents' combined income and the number of children. Our calculator computes and displays it so the math isn't a black box.
SB 343 refined how the guideline treats low-income parents and larger families and took effect in 2024. Our calculator uses the current §4055 formula.
It applies the same §4055 formula and shows every step, but it isn't a Judicial Council–certified calculator and takes net income directly rather than deriving it from gross pay. Use it to understand and prepare, then confirm the exact figure on a certified tool.
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