Income shares child support calculator

How the income shares model works

1. Add both parents' gross monthly income to get combined income.
2. Look up the state's Schedule of Basic Child Support Obligations for that combined income and number of children.
3. Calculate each parent's share of combined income (Parent A income ÷ combined).
4. Multiply the basic obligation by each parent's share.
5. Apply a parenting time credit to the parent paying support if their overnights exceed the state threshold.
6. Add health insurance, childcare, and extraordinary medical add-ons proportionally.

States that use income shares

Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Florida, Georgia, Idaho, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Nebraska, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Utah, Vermont, Virginia, Washington, West Virginia, Wyoming.

Understanding the Income Shares Model

The Income Shares model is the most widely used child support formula in the United States. Forty-one states and the District of Columbia use it to calculate monthly child support obligations. The model is built on one core principle: a child should receive the same proportion of parental income they would have received if both parents were still living together. When a household splits into two, the financial support for the children should not.

The model gets its name from the fact that both parents contribute their share. Unlike older formulas that looked only at what the paying parent earned, Income Shares treats child-rearing as a shared financial responsibility. Both parents' incomes go into the formula. Both parents pay their proportional share of the total obligation.

The Mathematical Foundation

The Income Shares formula follows a four-step process.

First, both parents' gross monthly incomes are combined into a single figure called the combined gross monthly income. This is the financial starting point for every calculation. Second, the combined income is matched against the state's Schedule of Basic Child Support Obligations — a table built by economists that estimates what parents at various income levels spend each month on their children's food, housing, clothing, transportation, and education. The schedule produces the total monthly obligation. Third, each parent's individual income is divided by the combined total to calculate their income share percentage. If Parent A earns $6,000 and Parent B earns $3,000, the combined income is $9,000. Parent A's income share is 66.7 percent. Parent B's income share is 33.3 percent. Fourth, the basic obligation is multiplied by each parent's income share to determine their individual monthly contribution.

The parent with less parenting time transfers their share to the parent with more parenting time. Healthcare premiums for the children and work-related childcare costs are then added on top of the base obligation and split proportionally by the same income percentages.

What This Calculator Measures

This calculator runs the Income Shares formula using the inputs you provide. It produces a monthly estimate based on combined income, number of children, parenting time, and add-on expenses. The result reflects the guideline amount your state would likely order given those inputs.

The calculator does not capture every factor a court considers. Judges can deviate from the guideline when circumstances warrant it. Imputed income, unusual expenses, a child's special needs, and extraordinary parenting arrangements can all affect the final order. The calculator gives you the formula result — courts apply judgment on top of that.

Step-by-Step Guide to Getting an Accurate Estimate

Getting a useful result requires accurate inputs. Here is how to approach each field.

Combined gross income. Gross income means income before taxes, before health insurance deductions, and before retirement contributions. Include wages, salary, overtime, bonuses, self-employment profit, rental income, and any other regular income source. Do not enter your take-home pay. For variable income — commission-based work, seasonal employment, or self-employment — average the last 12 months and divide by 12.

Number of children. Enter only the children covered by this order. Children from other relationships are handled separately through the imputed income and prior obligation adjustment process.

Parenting time percentage. Count the actual number of overnights per year the paying parent has with the children. Divide that number by 365. Every-other-weekend schedules run roughly 14 to 20 percent. Equal parenting time is 50 percent. Enter your actual overnight count rather than estimating — small differences near state thresholds can change whether a parenting time credit applies.

Healthcare costs. Enter only the portion of the health insurance premium that covers the children. Ask your HR department for the cost difference between the employee-only plan and the employee-plus-children plan if you are unsure of the exact children's share.

Childcare costs. Enter work-related childcare expenses only. Costs that allow either parent to maintain employment — daycare, after-school programs, and summer care — qualify. Costs for other purposes do not.

How to Read Your Results

The results section shows every line of the calculation. The combined monthly income sets the starting point. The basic support obligation comes from the state schedule at that combined income level. Each parent's income share percentage shows how the obligation splits between them. The parenting time credit line shows any reduction applied for the paying parent's overnights. Add-on costs are shown as a proportional allocation. The final obligation is the net monthly transfer from the paying parent to the receiving parent.

If the result looks significantly higher or lower than expected, the gross income entry is almost always the reason. Entering take-home pay instead of gross income produces a result 20 to 30 percent below the actual guideline amount in most states.

When the Guideline Amount Changes

Courts can order an amount above or below the guideline when written findings support it. Common reasons include a child's extraordinary medical or educational needs, a parent's extraordinary debt obligations, a high income that makes the schedule amount exceed the children's reasonable needs, or a parenting arrangement that the standard formula does not capture accurately.

Both parents can also agree to a different amount as part of a negotiated settlement. Courts will typically approve an agreed-upon amount as long as it meets a minimum threshold for the children's basic needs.

Knowing When to Talk to an Attorney

This calculator gives you a reliable estimate based on the guideline formula. An attorney gives you something the calculator cannot: judgment about your specific case. If income is disputed, if one parent's finances are complex, if a deviation is likely, or if you are preparing for a modification hearing, a licensed family law attorney in your state can review your numbers and advise on your options. Most offer a free initial consultation.

Get a free child support consultation with a licensed family law attorney in your state.