Child Support Calculator
Free child support estimate using a simplified income-shares guideline. Enter both parents' incomes, custody nights, and child count.
What this child support estimate is
Child support in most US states follows an income-shares model: the parents’ incomes are added together, a basic obligation is assigned for the number of children, and each parent is charged their share of that obligation by income. This calculator approximates that model so you can sanity-check a number before a formal calculation. It is a planning estimate, not legal advice, and real awards can differ by 30% or more in either direction.
How the estimate is built
- Combined income is parent A’s gross monthly income plus parent B’s.
- A basic obligation is applied to the combined income using a set of percentages that rises with the number of children.
- The higher earner is treated as the paying parent. Their share is their income divided by the combined income.
- Their share of the basic obligation is the starting support figure.
- A parenting-time credit reduces that figure once the paying parent has the children for a substantial number of nights a year.
A worked example
Parent A earns $5,000 a month, parent B earns $3,000, there are two children, and the children spend 104 nights a year with the higher earner:
| Step | Calculation | Result |
|---|---|---|
| Combined monthly income | 5,000 + 3,000 | $8,000 |
| Basic obligation (2 children) | 8,000 × 28% | $2,240 |
| Higher earner’s share | 5,000 ÷ 8,000 | 63% |
| Support before time credit | 2,240 × 0.63 | $1,400 |
| Parenting-time credit (104 nights) | reduction of ~14% | −$200 |
| Estimated monthly support | $1,201 | |
| Estimated annual support | 1,201 × 12 | $14,407 |
The simplified obligation schedule
These are the percentages the calculator applies to combined monthly income. They approximate the middle of the range across states.
| Children | Applied up to $10,000/month | Marginal rate above $10,000 |
|---|---|---|
| 1 | 20% | 10% |
| 2 | 28% | 13% |
| 3 | 36% | 16% |
| 4 | 40% | 18% |
| 5 | 45% | 20% |
| 6 or more | 50% | 22% |
How the parenting-time credit works
Once the paying parent has the children for roughly 73 nights a year or more, the estimate reduces in proportion to that time — about a 10% reduction at 20% of nights, rising to a 25% reduction at a true 50/50 split. This is a approximation of the shared-custody adjustments states apply, and it is one of the places a real order most often diverges from an estimate.
What a real order adds that this does not
- Health insurance and medical costs, split between parents.
- Childcare and work-related care for younger children.
- Extraordinary expenses such as special needs, travel for visitation, or private school.
- Tax adjustments, including which parent claims the dependency exemption.
- State-specific tables, self-employment deductions, and imputed income for a non-working parent.
Common mistakes
- Treating the number as the final order. It is a rough approximation; a court or agency figure governs.
- Using net instead of gross income. Guideline tables are usually fed gross income, a point many people get wrong.
- Ignoring overtime and bonuses. Variable pay is typically averaged in, which changes the number.
- Assuming one state’s table fits all. The model here is a generalisation; your state may weight income differently or cap obligations.
Frequently asked questions
Is this a legal calculation I can rely on?
No. It is a planning estimate built on a simplified income-shares model. For a figure you can act on, use your state’s official child support calculator or speak to a family lawyer, and verify every input against your actual documents.
How does 50/50 custody change the number?
A true equal-timeshare does not normally reduce support to zero. It reduces the obligation, and this estimate applies roughly a 25% cut at 50/50. State formulas also bring both parents’ direct expenses into the calculation, so the final figure can move either way.
Does my new partner’s income count?
Usually not. Guideline calculations generally look at the legal parents’ incomes. A new partner’s earnings can matter indirectly if they change household expenses or if a parent voluntarily reduces their own income, but they are not simply added to the obligation.
What if a parent is self-employed or paid irregularly?
Courts typically average several years of income or impute a figure based on earning capacity. Enter a realistic monthly average for a rough estimate, and expect the formal process to dig into tax returns and business accounts. Converting an annual figure to monthly is a good first step — the salary converter does it quickly.
The share split that drives this estimate is just percentage arithmetic, which a percentage calculator can show directly. And because support is a share of income, any change to either parent’s pay changes the result — rerun the estimate whenever income shifts materially.