Estimate guideline child support using California's statewide formula — updated for the SB 343 changes effective September 1, 2024 — with a transparent step-by-step breakdown.
This educational estimate is not legal advice and is not the court figure. California courts use the official Department of Child Support Services Guideline Calculator and a judge can deviate for good cause. Determining net disposable income correctly requires tax and legal analysis.
California does not use a simple income-shares table like many states. It uses a statewide algebraic guideline in Family Code § 4055. The presumptively correct amount comes out of a single formula applied to both parents' net disposable income and their share of parenting time. Because the inputs interact, small changes in income or timeshare can move the result more than people expect — and that is exactly why this page shows every step instead of just a final number.
The base support for one child is:
CS = K [ HN − (H%)(TN) ]
SB 343 is the first significant overhaul of the guideline since 1992. Most online calculators still reflect the old rules — this page uses the new ones.
| Total Net Disposable Income / month (TN) | K Factor |
|---|---|
| $0 – $2,900 | 0.165 + TN ÷ 82,857 |
| $2,901 – $5,000 | 0.131 + TN ÷ 42,149 |
| $5,001 – $10,000 | 0.25 |
| $10,001 – $15,000 | 0.10 + 1,499 ÷ TN |
| Over $15,000 | 0.12 + 1,200 ÷ TN |
The bands are designed to connect smoothly, so K stays near 0.20–0.25 across most household incomes.
| Children | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
|---|---|---|---|---|---|---|---|---|---|---|
| Multiplier | 1.0 | 1.6 | 2.0 | 2.3 | 2.5 | 2.625 | 2.75 | 2.813 | 2.844 | 2.86 |
The formula is exact, but it only works with correct net disposable income. Under Family Code §§ 4058–4059, that is gross income from nearly all sources minus income taxes, FICA, mandatory California SDI, health insurance premiums, mandatory union dues, mandatory retirement contributions, job-related expenses, and any existing child or spousal support actually being paid. It is not your paycheck's take-home line. Getting this figure right is where the official calculator and an attorney earn their keep.
If the parent who owes support has net disposable income below full-time state minimum wage — about $2,929 per month in 2026 ($16.90/hour × 40 hours × 52 weeks ÷ 12) — a rebuttable low-income adjustment reduces the guideline amount, scaled by how far below the line the obligor falls. SB 343 made this consistent statewide.
On top of base support, the court adds mandatory add-ons (work-related childcare and the children's reasonable uninsured health costs) and may add discretionary ones (education, special needs). Since September 1, 2024, these are divided in proportion to each parent's net income, so the higher earner generally carries the larger share.
States like Alabama and Arizona use an "income shares" table — look up combined income, read off a number. California instead solves a formula where parenting time is a direct variable. That makes California support unusually sensitive to the custody schedule and is why California parents almost always negotiate timeshare and support together.