How to Fill Out California’s Child Support Calculator, Line by Line

What do you need before you start?

The calculator times out after 30 minutes of inactivity, so it is worth having everything in front of you before you begin:

• Both parents’ most recent tax return(s)
• Recent pay stubs, W-2s, and/or 1099s
• Documentation of health insurance premiums, retirement contributions, union dues, or other support obligations
• The current custody and parenting time schedule

If you want a rough sense of the number before working through the full official tool, our simplified child support estimator applies the same underlying formula to three inputs. It is a ballpark figure only — the official calculator is the one to use for anything you plan to file.

1. Information about the children

Number of Children to Use in the Calculation. Count only the children the two parents have in common. Do not include stepchildren or children from other relationships here — those are factored in elsewhere, as hardship deductions.

Time with Parent 1. This is the percentage of time “Parent 1” actually spends with each child — not what an old court order says, but the real, current schedule. If you are not sure how to convert a schedule (like “every other weekend plus Wednesdays”) into a percentage, the calculator’s Advanced Timeshare link offers pre-built options and an adjustment field for things like extra vacation weeks. Our custody timeshare calculator can also work this percentage out from a schedule you build day by day.

This number matters more than people expect — even a small shift in timeshare percentage can move the support amount noticeably.

Tip: The calculator lets you decide who is “Parent 1” and who is “Parent 2.” It is usually easier to make Parent 1 the one with less time with the children, but as long as you are consistent throughout the whole form, either order works.

2. Tax information

This section sets up how the calculator figures each parent’s net income — because guideline support is based on net disposable income, not gross pay.

• Tax Year — Defaults to the current year; change it only if you are calculating support for a past period.
• Federal Tax Filing Status — Single, Head of Household, Married Filing Jointly, or Married Filing Separately, based on each parent’s actual marital and filing situation as of the end of the relevant year.
• Federal Tax Exemptions / Number of Children for Child Tax Credit, Child Care Credit, Earned Income Credit — These reflect who claims each child on their taxes. Only one parent can claim a given child’s exemption or credit in a given year, and it typically matches the tax return — unless there is a signed IRS Form 8332 shifting that right to the other parent.
• State Income Taxes — Defaults to California. Change this only if a parent files taxes in another state.
• Other Tax Settings (self-employment tax, FICA, Medicare, Earned Income Credit) — These checkboxes are pre-filled based on your earlier answers. Leave them as-is unless you know a specific box does not apply — for example, uncheck “Self-Employment Taxes” if the parent is a W-2 employee only.

Where to find this: most of this section comes straight off a recent tax return (Form 1040) or W-2.

3. Monthly income information

Every dollar figure entered here must be a monthly amount. If you are working from a weekly, biweekly, or annual figure, use the calculator’s built-in Calculate Wages/Salary converter — or this quick reference:

Key fields in this section:

• Wages/Salary — Gross pay from employment, found on a W-2 (Box 5) or recent pay stub.
• Self-Employment Income — Gross business income minus business expenses (Schedule C of the tax return). Courts sometimes scrutinize claimed business expenses closely, especially depreciation or personal-use vehicle costs.
• Unemployment Compensation / Paid Family Leave and Disability (Taxable) — From IRS Form 1099-G or the parent’s pay stub.
• Other Taxable Income — A catch-all for capital gains, dividends, rental income, royalties, and similar sources; expand this section to enter each type individually if it applies.
• Other Non-Taxable Income — Nontaxable Social Security, tax-exempt interest, VA disability, or workers’ compensation. Important: enter these either as one lump sum in the general field, or itemized in the “Details” subsection — never both, or the calculator will double-count the income.
• New Spouse Wages/Income — A new spouse’s income is not counted as available for this child support case, but the calculator still asks for it because it affects the parent’s household tax picture, and therefore their net income.

4. Monthly deduction information

This is where allowable expenses get subtracted to arrive at net disposable income.

• Child Support Paid (Other Relationships) and Spousal Support Paid (This Relationship) — Amounts the parent is actually paying under an existing court order.
• Health Insurance Premiums — Premiums the parent pays for themselves and any children they support. The calculator asks whether this is paid pre-tax or post-tax; a pay stub will say which.
• Mandatory Retirement (Tax-Deferred) — Retirement contributions the employer requires, not voluntary 401(k) or IRA contributions above the required amount. Those go in a separate “Voluntary Retirement” field.
• Required Union Dues — Mandatory dues as a condition of employment (found on Schedule A of a tax return, if itemized).
• Property Tax / Mortgage Interest — Enter these only if the parent itemizes deductions rather than taking the standard deduction.
• Job-Related Expenses & Spousal Support (Other Relationship) — Necessary, unreimbursed work expenses, and support obligations to a different ex-spouse or partner.
• Extraordinary Health Expenses / Uninsured Catastrophic Losses — Courts may (not must) factor these in — for example, major uninsured medical costs, or an uninsured loss like fire or flood damage, entered as the monthly amount actually being paid toward that loss.

5. Hardship children

If a parent is financially responsible for other children living in their home from a different relationship, this section lets the calculator apply a “hardship” deduction. You can let the calculator compute this automatically based on the number of such children, or enter the parent’s actual documented expenses for them — whichever the calculator’s instructions indicate is appropriate for your case. This deduction is capped by law and does not reduce support dollar-for-dollar.

6. Monthly child support add-ons

Separate from base support, the calculator tracks certain shared child-related costs:

• Child Care (work- or training-related)
• Visitation Travel Expenses
• School Expenses (special needs or educational costs)
• Uninsured Health Expenses

You will also choose how these add-ons are divided between the parents — split 50/50, prorated based on adjusted income, or another method, depending on which guideline version applies to your case.

7. Other settings

• Low-Income Adjustment — Since September 2024, a paying parent whose net income falls below full-time minimum wage may qualify for a reduced support amount. If you are unsure of a parent’s exact net income before running the calculation, the state’s guidance is to select “Yes” here.
• Temporary Spousal Support — Optional. Several counties (Santa Clara, Alameda, Marin, and others) each use their own formula. This is separate from child support and applies only if you are also calculating temporary spousal support for a pending case.

8. Running the calculation

Click Calculate, and the results appear in a few sections:

• Monthly Support Totals — the bottom-line number: what one parent pays the other.
• Monthly Child Support Per Child — the breakdown by child.
• Monthly Tax/Income Information — a summary of the income, deductions, and tax liabilities the calculator used.
• Other Monthly Deduction Totals — hardship deductions, if any were applied.

You can click View Printable Results for a full report to save or bring to court, and Start Over to clear everything and run a new scenario.

Why the number might come out differently for each parent

It is common for two people in the same case to get two different results — not because the calculator is wrong, but because they entered different assumptions: a different timeshare percentage, a different guess about who claims which tax credit, or a different read on what counts as “mandatory” versus “voluntary” retirement contributions. This is exactly the kind of detail that is easy to get wrong without a second set of eyes — and exactly where document preparation support is useful, even though it is not legal advice.

Frequently asked questions

Which children do I count in the California child support calculator?

Count only the children the two parents have in common. Stepchildren and children from other relationships are not entered in the children field; if a parent supports other children living in their home, those are handled separately as a hardship deduction.

Does the calculator use gross or net income?

California guideline support is based on net disposable income, not gross pay. You enter gross figures and allowable deductions, and the calculator computes each parent's net using the tax information you provide.

How do I convert my pay into a monthly amount?

Every dollar figure in the income section must be monthly. Divide an annual figure by 12; multiply a weekly figure by 52 then divide by 12; multiply a bi-weekly figure by 26 then divide by 12; multiply a semi-monthly figure by 2. The calculator also has a built-in Calculate Wages/Salary converter.

Is a new spouse's income counted for child support?

A new spouse's income is not treated as available for the child support case itself, but the calculator still asks for it because it affects the household tax picture, and therefore the parent's net income.

Why do my ex and I get different numbers from the same calculator?

Almost always because of different inputs rather than a calculator error: a different timeshare percentage, a different assumption about who claims a tax credit, or a different read on what counts as mandatory versus voluntary retirement contributions.

Can I use a calculator result as my child support order?

No. The calculator produces an estimate. Only a family law judge or child support commissioner can set an actual support order, and California Rule of Court 5.275 requires a certified program be used in formal proceedings.

Primary sources

• California Guideline Child Support Calculator (the official DCSS tool)
• California Family Code § 4055 (the statewide uniform guideline formula)
• California Courts Self-Help — Child Support