California child support calculator 2026

California Child Support Calculator: How Timeshare Changes Your Number

California child support uses a formula that weighs two primary factors: each parent's net disposable income and the percentage of time each parent spends with the child. Because timeshare percentage sits directly in the formula, increasing your custody time — even by 7 or 8 percentage points — can reduce support meaningfully in a typical middle-income case.

Reviewed for:

  • Accuracy of California Family Code §§ 4050–4076 references
  • Statewide Uniform Guideline formula components
  • Timeshare percentage sensitivity analysis

Reviewed by Amit Sharma · How CustodyBuilder Works · Last updated August 2026 · Educational information only. Not legal advice.

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California §4055 Guideline Calculator

Enter income & timeshare

Use net monthly disposable income after taxes and mandatory deductions. Version CA-CS-2026.1.

Timeshare (H) is the high earner's fraction of total overnights.
Add-ons & spousal support (§4062) +

Estimated Monthly Support

$1,350.26

Parent B pays Parent A — planning estimate only.

High earner: Parent B | H = 27.4% | K = 0.2865

Show calculation receipt ▾
  1. Net disposable income A $4000.00
  2. Net disposable income B $8000.00
  3. Total net (TN) $12000.00
  4. High earner B
  5. High earner timeshare (H) 27.4%
  6. K bracket $10k < TN ≤ $15k
  7. Base K 0.224917
  8. H multiplier (1+H) 1.273973
  9. Final K 0.286538
  10. One-child guideline (CS1) $1350.26
  11. Child multiplier (1 children) 1.000
  12. Base support (CS) $1350.26
  13. Add-ons (§4062) $0.00
  14. Final support $1350.26/month [B → A]
  15. Calculator version CA-CS-2026.1

Estimate based on California Family Code §4055 guideline formula (CA-CS-2026.1). Add-ons are calculated separately under §4062. Your actual order may differ. Consult a licensed California family law attorney.

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How California Calculates Child Support

Law: California Family Code § 4055 sets the formula. Courts and attorneys use licensed software (Dissomaster or XSpouse) that inputs the variables, but the underlying formula is public.

The core formula simplified:

CS = K × (HN − (H% × TN))

  • CS = child support
  • K = combined income factor (decreases as combined income rises)
  • HN = high earner's net disposable monthly income
  • H% = high earner's approximate timeshare percentage
  • TN = total net disposable income of both parents

Key insight: H% — the high earner's timeshare — sits in the middle of the formula. When the high earner has more custody time, H% increases, and the support amount drops. This is why parenting time and support are inseparable conversations in California.

Calculator assumption: This calculator applies the published formula components under Family Code § 4055 to your entered income and timeshare figures. It treats all income as fixed monthly net income. Variable income, imputed income, and high-income deviations are not automatically modeled.

The Timeshare Effect: Concrete Numbers

Timeshare percentage is the variable parents most often underestimate entering negotiations. Agreeing to 35% custody instead of 28% could substantially change monthly support over years — because timeshare percentage is directly incorporated into the § 4055 formula.

Example CA-001

Parenting time sensitivity at a single income level

Parent A (high earner) nets $6,500/month, Parent B nets $2,800/month, one child.

Timeshare (Parent A)Estimated Support Owed by Parent A
20%~$1,480/month
28%~$1,240/month
35%~$950/month
40%~$780/month
50%~$480/month

Based on formula components under Family Code § 4055. The reduction is not linear; it is steeper at lower timeshare levels. Your result will differ.

Calculate your timeshare % → Overnight custody calculator Parenting time calculator

What changes your estimate the most?

Based on the published formula components for a family with $10,000/month combined net disposable income and one child:

Change to the inputsEstimated effect on monthly support
High earner timeshare increases from 28% to 35%Support decreases ~$200–$350/month
High earner timeshare increases from 35% to 42%Support decreases ~$150–$250/month
High earner net income increases by $1,000/monthSupport increases ~$100–$160/month
Lower earner net income increases by $1,000/monthSupport decreases ~$60–$100/month
$400/month childcare add-on (§ 4062) addedSupport increases ~$200/month (split 50/50 by default)

Worked Examples

Example CA-002

Miguel earns $120k salary. Sandra earns $120k from her business. Why the inputs differ.

Both report $8,000/month gross income. Miguel is a salaried engineer; Sandra runs a consulting business.

Miguel's net disposable: ~$5,216/month

After federal/state taxes, FICA, SDI, health insurance

Sandra's net disposable: ~$3,700/month

After business expenses, self-employment tax (15.3%), income taxes, health insurance

Even though both start at "$8,000/month," Sandra's net disposable income for support purposes is roughly 29% lower. This is why the formula inputs matter more than the headline income figure.

Example CA-003

Marcus increases his parenting time from 28% to 35%. How much does it change support?

Marcus earns $7,200/month net disposable. Elena earns $3,100/month. One child.

  • At 28% timeshare (~102 overnights/year): estimated support approximately $1,050/month owed by Marcus
  • At 35% timeshare (~128 overnights/year): estimated support approximately $790/month owed by Marcus

Moving from 28% to 35% parenting time is a reduction of roughly $260/month, or $3,120/year. Over a 10-year support obligation, that schedule decision is worth roughly $31,000. Your result will differ.

What "Net Disposable Income" Means in California

Net disposable income in California is gross income after a long list of deductions — taxes, FICA, health insurance, union dues, and certain mandatory expenses. It is not take-home pay.

Deducted from gross

  • Federal and state income taxes (at actual rate)
  • FICA (Social Security and Medicare)
  • State disability insurance (SDI)
  • Mandatory union dues
  • Health insurance premiums (for yourself and the children)
  • Hardship deductions for supporting other minor children

Not deducted

  • Voluntary retirement contributions beyond the minimum
  • Discretionary spending
  • New spouse's income (though remarriage changes tax calculations)
Law: New spouse income is excluded from the California child support calculation under Family Code § 4057.5. However, remarriage changes your tax filing status, which changes your net disposable income calculation, which changes your support number. Family law software accounts for this automatically; many parents don't understand why their support number shifted after remarrying.

Add-Ons Beyond Guideline Support

Guideline support covers basic needs. Childcare, healthcare, and certain other expenses are add-ons — always split 50/50 unless income disparity justifies adjustment.

Law: California Family Code § 4062 requires courts to order these additional expenses on top of guideline support.
Add-OnDefault SplitNotes
Childcare (work/education related)50/50*Only childcare that allows the parent to work or attend school
Uninsured healthcare costs50/50*Copays, deductibles, treatments not covered
Education and special needs50/50*Special schooling, tutoring for documented needs
Travel for visitationNegotiatedCourts can allocate based on who caused the distance

What parents miss: A $1,200/month support order alongside $800/month in daycare costs means the real support arrangement is $1,600/month after the 50/50 daycare split — 33% higher than the support order alone suggests.

High-Income Cases: When Courts Deviate Upward

Law: Under California Family Code § 4057, courts can deviate from guideline support in both directions. In high-income cases, when a court exercises discretion to deviate, the deviation may increase or decrease the guideline amount depending on the circumstances.

In high-asset cases, courts scrutinize lifestyle evidence: private school enrollment, vacation patterns, activity costs. The guideline provides a floor, not a ceiling, when combined parental income is high and the formula result looks obviously inadequate compared to the family's established expenses.

Self-Employment Income in California

California imputes income based on earning capacity, not just what you report — self-employed parents who underreport income face significant risk.

California courts have broad authority to impute income to a parent based on their earning capacity. For self-employed parents: courts examine business tax returns (Schedule C/K-1) for 2–3 years, business bank records, whether business expenses are genuine or inflated, and whether the parent is voluntarily working below capacity.

Common trap: A self-employed parent who moves income into the business to reduce personal income, then takes personal benefits (car, phone, meals) through the business, will see those "add-backs" in the income calculation. Courts are familiar with this pattern.

Common Mistakes

Not accounting for add-ons when evaluating an offer

A support number without the add-on split looks much lower than the true obligation. Always calculate childcare and healthcare add-ons before accepting or rejecting a settlement offer.

Underreporting self-employment income

Courts are experienced with this. Forensic accountants may be appointed in contested cases involving complex or disputed business income. Penalties include retroactive support, attorney's fees, and potential contempt.

Not knowing that even $1 of income difference matters

California's formula is continuous, not a step function. Every dollar of net income and every fraction of a percent of timeshare changes the result. Don't round numbers when running scenarios.

Assuming the guideline is a ceiling

In high-income cases, it's a floor. Judges have authority to go higher when the guideline doesn't maintain the child's accustomed standard of living.

Forgetting that a new spouse affects the calculation

Not directly — the spouse's income doesn't count under Family Code § 4057.5 — but remarriage changes tax filing status and therefore net disposable income. Run the numbers again after any major household change.

Treating custody time as only a parenting question

In California, timeshare percentage is a primary variable in the support formula. Agreeing to a custody schedule without understanding its support implications is one of the most expensive mistakes in California family law.

See How Your Custody Schedule Affects Support

In California, custody schedule and support amount are not separate conversations — they are the same conversation. Changing your schedule by 5–10 percentage points shifts the support number meaningfully.

Custody Percentage Calculator

See exactly what percentage of time your schedule gives each parent — the key formula input.

Custody Schedule Generator

Build your schedule and download as PDF, free.

Overnight Custody Calculator

Count overnights per year by schedule type.

California Custody Schedule

Common California schedule patterns and how they map to timeshare percentages.

California Parenting Plan Template

Template formatted for California family courts.

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FAQ

California Child Support — Frequently Asked Questions

Common questions about California's Statewide Uniform Guideline, timeshare percentage, and add-on expenses.

Can parents agree to a support amount different from the guideline in California?

Yes, with limitations. Courts can approve a non-guideline agreement if both parents are represented by counsel, the agreement is knowing and voluntary, and it is in the child's interest. Courts will not approve an agreement that leaves the child inadequately supported.

Does California have a support calculator I can use myself?

The Judicial Council's child support calculator (available at the California Courts website) runs the same formula as Dissomaster. It is publicly available but requires accurate income inputs and doesn't account for all variables the software handles.

What happens if my income changes significantly after the order?

Either parent can petition for modification when there is a change in circumstances — a meaningful change in either parent's income or in the custody schedule. California courts don't require a specific percentage threshold, though modest changes may not justify the cost and complexity of a modification proceeding.

Does overtime count as income in California?

Generally yes. California courts include regular overtime in income. If overtime is genuinely irregular (a one-time emergency project), you may be able to argue it shouldn't be included, but recurring overtime is treated as income.

How does California handle parents who quit their jobs to reduce support?

Courts impute income based on earning capacity. If a parent voluntarily leaves employment, courts use their prior income or their capacity to earn as the basis for the calculation — not $0.

Does the California formula change for multiple children?

Yes — the K factor in the formula adjusts for number of children. Support does not simply multiply by the number of children; the formula produces a blended result that increases with additional children but not proportionally.

What is the difference between guideline and add-on support in California?

Guideline support (from the formula) covers basic expenses: food, clothing, shelter, routine healthcare. Add-on support under § 4062 covers specific costs beyond basics — childcare, uninsured medical expenses, and special needs costs. Both are part of the total support obligation.

Can the court order support before the case is finalized?

Yes. Courts may issue temporary support orders while a case is pending. Timelines vary by county and court backlog. Temporary orders use the same formula and are enforceable immediately.

Sources

  1. [1] California Legislative Information — Family Code § 4055, Statewide Uniform Guideline formula — last verified August 6, 2026
  2. [2] California Legislative Information — Family Code § 4062, Additional child support — last verified August 6, 2026
  3. [3] California Legislative Information — Family Code § 4057, Deviation from guideline — last verified August 6, 2026
  4. [4] California Legislative Information — Family Code § 4057.5, New spouse income — last verified August 6, 2026

This content is for informational and educational purposes only. It does not constitute legal advice and does not create an attorney-client relationship. California child support calculations require licensed software, complete financial disclosure, and judicial discretion. Consult a licensed family law attorney in California before making decisions about child support or custody.