Calculation of Child Support

In California, child support is calculated with a very complex algebraic formula that takes into consideration the parents' incomes, each parent's time with the child and any tax deductions that are available to either parent. This formula is applied whenever the support of a minor child is to be determined, including dissolutions, paternity and domestic partnership cases. Click HERE to go to the official State of California Child Support Services child support calculator.


Purposes of the Guideline

There are two purposes for the guideline: (1) To provide for a minimum level of child support for a child and (2) To provide for uniformity in the calculation of child support. In order to achieve these purposes the guideline requires judges to follow its provisions, with deviations allowed only in limited and specified situations.

Underlying Principles

The guideline statute begins by setting forth the principles that are to be followed in its implementation. Among those principles are the following:

  • A parent's first and principal obligation is to support his or her minor children according to the parent's circumstances and station in life.
  • Both parents are mutually responsible for the support of their children.
  • The guideline is intended to be presumptively correct in all cases, and only under special circumstances should child support orders fall below the child support mandated by the guideline formula.
  • Child support orders must ensure that children actually receive fair, timely, and sufficient support reflecting the state's high standard of living and high costs of raising children compared to other states.

Applying the Guideline

The guideline itself is a very complex algebraic formula. The actual formula is set out in full in the Appendix at the end of this article. Because of the complexity of the formula, computer programs are required in order that quick and accurate calculations can be obtained. By far the most commonly used program is DissoMaster©, which can be found at the following website:

To determine the child support guideline for a child, the following in formation must be obtained:

  • The gross incomes of each parent.
  • The percentage of time each child spends with each parent.
  • Any available income tax deductions that the parents can claim, such as mortgage interest.
  • Mandatory payroll deductions, such as health insurance, pensions and union dues.
  • Child care costs incurred by either parent.

Once this basic information is inserted into the DissoMaster or other support calculation program, a guideline child support amount is generated.


The following are examples of how the child support guideline is applied in different factual situations. Note that in most of the examples, if the parents are married or in a domestic partnership, the higher income earner could be ordered to pay spousal support to the other parent in addition to the guideline child support. How that spousal support would be calculated is beyond the scope of this article.

Example 1

Facts: The father earns $7,000 per month and the mother earns $3,000 per month. There are two minor children and father has them 30% of the time. Each parent has $100 per month deducted from their paychecks for health insurance. Both parents have monthly mortgage interest payments of $1,200 and property taxes of $200 per month.

Support: Father pays mother $1,268 per month.

Example 2:

Facts: Same incomes, deductions and payments as in Example 1. However, the parent equally share the time with the children.

Support: Father pays mother $609 per month.

Example 3:

Facts: Father earns $7,000 per month and mother earns $5,500 per month. Same deductions and payments as in Example 1. Father has the children 40% of the time.

Support: Father pays mother $548 per month

Example 4:

Facts: Father earns $7,000 per month and mother is unemployed. Father has the children 25% of the time. Same deductions and payments as in Example 2.

Support: Father pays mother $1,914 per month

Deviations from the Guideline Amount

California Family Code §4057(a) states that the guideline amount of child support, as determined by the formula, is "presumed to be the correct amount of child support to be ordered." This means that the judge is required to order the guideline level of child support, unless there is a good reason why another amount of child support would be appropriate.

In creating the child support guideline the California legislature understood that there may be situations when the mechanical application of the guideline would not be fair or reasonable. Family Code §4057(b) contains a list of factors which, if present, can justify a judge's decision to award child support that is higher or lower than the amount generated by the guideline formula. Among those factors are the following:

  • The parent being ordered to pay child support has an extraordinarily high income and the amount determined under the formula would exceed the needs of the children.
  • A parent party is not contributing to the needs of the children at a level commensurate with that parent's custodial time.
  • Cases in which both parents have substantially equal time-sharing of the children and one parent has a much lower or higher percentage of income used for housing than the other parent.
  • Cases in which the children have special medical or other needs that could require child support that would be greater than the formula amount.

Child Support Add-Ons

In addition to the basic child support guideline amount, a parent can be ordered to contribute to specified expenses that are for the benefit of the children. Family Code §4062 lists two types of child support add-ons.

Mandatory Add-Ons: The judge is required to order a contribution to the following as additional child support: (1) Child care costs related to employment or to reasonably necessary education or training for employment skills; and (2) The reasonable uninsured health care costs for the children.

Discretionary Add-Ons: The judge can also order a parent to contribute to: (1) Costs related to the educational or other special needs of the children; and (2) Travel expenses for visitation. (This appears to refer only to travel expenses incurred by the custodial parent.)

If the judge makes orders for any child support add-ons, any such expenses are usually equally shared by the parents. However, where an equal allocation of these expenses is not reasonable, the court is authorized to allocate them between the parents in proportion to their net spendable incomes. Family Code §4061(b) provides that the following three-step procedure is to be followed to determine the parents' respective net spendable incomes for purposes of allocating the child support add-ons:

Step One: The guideline child support amount is to be calculated.

Step Two: The amount of guideline child support is deducted from the income of the paying parent but not added to the income of the receiving parent.
Step Three: If one parent is paying spousal support to the other parent, the amount of spousal support is to be deducted from the income of the paying parent and added to the income of the receiving parent.
Step Four: Calculate the father's percentage of the parents' combined incomes and apply that percentage to the add-on.

For example, in Example 1, above, if the father has been ordered to pay spousal support of $487 per month to the mother and the mother has a monthly child care expense of $800, the proportionate sharing that expense would be calculated as follows:

Step One: The father's guideline child support has been calculated to be $1,268.
Step Two: Deducting the guideline child support from the father's income results in a difference of $5,732.
Step Three: Deducting the spousal support of $487 from the father's net income and adding it to the mother's income results in net incomes of $5,245 for father and $3,487 for month, for a total combined net income of $8,732.
Step Four: Father's percentage is 66% of the total combined net income. That percentage is then multiplied by the child care expense, which results in the father's share of the monthly child care expense being calculated at $528. Conversely, the mother's share would be the difference between $800 and $528, which is $272.

Appendix 1: The Statewide Child Support Guideline
Family Code §4055

(a) The statewide uniform guideline for determining child support orders is as follows: CS = K (HN - (H%) (TN)).
(b) (1) The components of the formula are as follows:
(A) CS = child support amount.
(B) K = amount of both parents' income to be allocated for child
support as set forth in paragraph (3).
(C) HN = high earner's net monthly disposable income.
(D) H% = approximate percentage of time that the high earner has or will have primary physical responsibility for the children compared to the other parent. In cases in which parents have different time-sharing arrangements for different children, H% equals the average of the approximate percentages of time the high earner parent spends with each child.
(E) TN = total net monthly disposable income of both parties.
(2) To compute net disposable income, see Section 4059.
(3) K (amount of both parents' income allocated for child support) equals one plus H% (if H% is less than or equal to 50 percent) or two minus H% (if H% is greater than 50 percent) times the following fraction:

Total Net Disposable
Income Per Month
$0-8000.20 + TN /16,000
$6,667-10,0000.10 + 1,000/TN
Over $10,0000.12 + 800/TN

For example, if H% equals 20 percent and the total monthly net disposable income of the parents is $1,000, K = (1 + 0.20) X 0.25, or .30. If H% equals 80 percent and the total monthly net disposable income of the parents is $1,000, K = (2 - 0.80) X 0.25, or 0.30.

(4) For more than one child, multiply CS by:
2 children 1.6
3 children 2
4 children 2.3
5 children 2.5
6 children 2.625
7 children 2.75
8 children 2.813
9 children 2.844
10 children 2.86