Child Support Calculator Inputs Explained

State child support calculators are free, accurate, and available to every parent. The problem is that they're built for court clerks and attorneys, not for parents using them for the first time. Each input field carries assumptions about what number to enter — and getting any of them wrong cascades through the entire calculation.

Gross Monthly Income (Not What You Think)

The first field asks for gross monthly income. This is your pre-tax, pre-deduction income from all sources — wages, commissions, bonuses, rental income, dividends, and some government benefits. It is not your direct deposit amount.

The confusion deepens based on how you're paid:

• Weekly: Multiply by 52, divide by 12 (multiply by 4.33, not 4)
• Bi-weekly: Multiply by 26, divide by 12
• Semi-monthly: Multiply by 2
• Monthly: Enter as-is

A parent paid $1,200 weekly who enters $4,800 per month (×4) instead of $5,200 (×4.33) underreports by $400 per month — enough to shift the final support amount by $50 to $100 monthly.

Allowable Deductions

Most calculators ask you to list deductions, but they don't explain which ones count. Courts generally allow:

• Federal and state income taxes actually paid
• FICA (Social Security and Medicare)
• Mandatory retirement contributions required by your employer
• Mandatory union dues
• Health insurance premiums (only the children's share in many states)

They typically disallow voluntary deductions: elective 401(k) contributions above employer match, HSA contributions, flexible spending accounts, charitable payroll deductions, and voluntary disability insurance. Entering these as deductions reduces your income on paper — and judges add them back.

Number of Children and Prior Orders

Calculators ask for the number of children in this case and whether you support children from prior relationships. If you have an existing child support order for children from a previous relationship, most states let you deduct that amount from your gross income before running the new calculation. Some states (like Georgia) use a "theoretical support order" set at 75% of the guideline amount rather than the actual amount paid.

Parenting Time Percentage

This field asks for the number of overnights each parent has per year. The word "overnights" is literal — the child must sleep at your residence. Daytime-only visits, vacation days where the child returns to the other parent's home at night, and after-school pickups don't count.

Specific thresholds matter enormously. In Florida, crossing 73 overnights (20% of the year) triggers the "gross-up method" — a completely different formula that can reduce the payor's obligation by hundreds of dollars per month. In Illinois, the threshold is 146 overnights. In California, it's built into a continuous sliding scale.

Health Insurance and Childcare

The final inputs ask for the cost of health insurance and work-related childcare. For health insurance, you typically enter only the children's portion — not the full family premium. If your family plan costs $800 per month and covers you plus two children (three people total), the children's share is $533 ($800 ÷ 3 × 2).

Childcare must be work-related — required so both parents can maintain employment. Summer camp costs, tutoring, and extracurricular activities usually don't go in this field (they're handled separately as add-on expenses).

Preparing Your Inputs Before You Calculate

The most common calculator errors aren't math problems — they're input problems. The Child Support Estimation Worksheet Guide walks you through gathering and verifying every input field before you open your state's calculator, so the numbers you enter actually reflect what the court expects to see.