Quick Answer: Child support in the United States is calculated using one of three formulas. The Income Shares Model is used by 41 states including California, the Percentage of Income Model is used by 6 states including Texas, and the Melson Formula is used by Delaware, Hawaii, and Montana. The calculation considers each parent’s gross income, the percentage of time each parent spends with the child, mandatory deductions, and the cost of healthcare and childcare. In California, the calculation is governed by California Family Code section 4055 and is performed using state-approved software such as Dissomaster.
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The Three Main Child Support Calculation Methods
Every US state has a mandatory child support guideline, required by federal law under 42 U.S.C. section 666. Each state’s guideline produces a presumptive support amount that the court must order unless a deviation is justified. Although all 50 states are required to have a guideline, they use one of three different mathematical approaches:
| Calculation Method | Number of States | Key Feature |
| Income Shares Model | 41 states (including California) | Considers both parents’ incomes combined |
| Percentage of Income Model | 6 states | Uses only the non-custodial parent’s income |
| Melson Formula | 3 states (Delaware, Hawaii, Montana) | Adds a Standard of Living Adjustment after basic needs |
The result is that the same family situation can produce very different child support orders depending on the state. A non-custodial parent earning $5,000 per month with two children may owe roughly $1,000 in one state and $1,400 in another, with no other facts changed.
The Income Shares Model Explained
The Income Shares Model is the most common approach. It is based on a simple principle: a child should receive the same proportion of parental income that the child would have received if the parents lived together.
Here is how the calculation works in concept:
- Add the gross monthly income of both parents to find combined parental income.
- Apply the state’s economic table or formula to determine the total monthly child support obligation based on combined income and number of children.
- Allocate the obligation between the parents in proportion to each parent’s share of the combined income.
- Adjust for additional support items such as health insurance premiums, childcare costs, and special needs expenses.
- Adjust for parenting time. The more time the non-custodial parent has with the child, the lower their direct support obligation usually becomes.
The Income Shares Model is considered the most equitable of the three approaches because it accounts for both parents’ incomes and reflects the actual cost of raising a child at that income level. It is used in 41 states including California, Florida, New York, and Illinois.
A Simplified Example Calculation
Consider a hypothetical two-parent family with the following details:
| Factor | Amount |
| Parent A monthly gross income | $6,000 |
| Parent B monthly gross income | $3,000 |
| Combined monthly income | $9,000 |
| Custodial parent timeshare | 70 percent |
| Number of children | 2 |
| Estimated guideline support (Parent A pays) | $1,250 per month |
In this example, Parent A earns 67 percent of combined income, so Parent A pays roughly 67 percent of the basic support obligation. Adjustments for healthcare costs, childcare, and the custodial timeshare reduce or increase this figure. The actual calculation in California would use Dissomaster software, which applies the state’s exact algebraic formula known as the K factor.
The Percentage of Income Model Explained
Six states use the Percentage of Income Model, which is simpler than Income Shares. In this model, only the non-custodial parent’s income matters. The court applies a flat percentage to that income, with the percentage increasing as the number of children increases.
The states currently using this model are Alaska, Mississippi, Nevada, North Dakota, Texas, and Wisconsin.
As an example, Texas uses the following percentages of net resources of the non-custodial parent under Texas Family Code section 154.125:
- One child: 20 percent of net resources
- Two children: 25 percent
- Three children: 30 percent
- Four children: 35 percent
- Five or more children: at least 40 percent
Critics argue this model is less fair because it ignores the custodial parent’s income entirely. A custodial parent earning a high income receives the same child support as a custodial parent earning nothing, when the non-custodial parent has the same income. Supporters argue the simplicity makes the system easier to enforce.
The Melson Formula Explained
The Melson Formula is the most complex of the three methods. It is used in Delaware, Hawaii, and Montana. The formula builds on the Income Shares approach and adds an additional step called the Standard of Living Adjustment, or SOLA.
In the Melson approach, the calculation proceeds as follows:
- Each parent’s income is reduced by a self-support reserve, ensuring the parent has enough income to meet basic personal needs.
- The basic primary support obligation of the child is calculated using economic tables.
- If income remains above the self-support reserve after basic support, a percentage of the remaining income is added as a Standard of Living Adjustment so the child shares in the parents’ standard of living.
The Melson Formula was designed by Family Court Judge Elwood Melson of Delaware in the 1970s. It is considered the most equitable but also the most complex to calculate without software.
Which Method Each State Uses
Here is a complete reference of which method each US state uses in 2026:
| State | Calculation Method Used |
| Alabama | Income Shares |
| Alaska | Percentage of Income |
| Arizona | Income Shares |
| Arkansas | Income Shares |
| California | Income Shares (Family Code section 4055) |
| Colorado | Income Shares |
| Connecticut | Income Shares |
| Delaware | Melson Formula |
| Florida | Income Shares |
| Georgia | Income Shares |
| Hawaii | Melson Formula |
| Idaho | Income Shares |
| Illinois | Income Shares |
| Indiana | Income Shares |
| Iowa | Income Shares |
| Kansas | Income Shares |
| Kentucky | Income Shares |
| Louisiana | Income Shares |
| Maine | Income Shares |
| Maryland | Income Shares |
| Massachusetts | Income Shares |
| Michigan | Income Shares |
| Minnesota | Income Shares |
| Mississippi | Percentage of Income |
| Missouri | Income Shares |
| Montana | Melson Formula |
| Nebraska | Income Shares |
| Nevada | Percentage of Income |
| New Hampshire | Income Shares |
| New Jersey | Income Shares |
| New Mexico | Income Shares |
| New York | Income Shares (post 2010) |
| North Carolina | Income Shares |
| North Dakota | Percentage of Income |
| Ohio | Income Shares |
| Oklahoma | Income Shares |
| Oregon | Income Shares |
| Pennsylvania | Income Shares |
| Rhode Island | Income Shares |
| South Carolina | Income Shares |
| South Dakota | Income Shares |
| Tennessee | Income Shares |
| Texas | Percentage of Income |
| Utah | Income Shares |
| Vermont | Income Shares |
| Virginia | Income Shares |
| Washington | Income Shares |
| West Virginia | Income Shares |
| Wisconsin | Percentage of Income |
| Wyoming | Income Shares |
Note that even within the same calculation method, states use different specific formulas, economic tables, and adjustment rules. The result is that no two states produce identical child support amounts for the same facts.
How California Calculates Child Support
California uses the Income Shares Model. The calculation is governed by California Family Code section 4055, which sets out the statewide uniform guideline formula. California requires courts to order the presumptively correct support amount unless specific findings justify a deviation under California Family Code section 4057. For more on the broader process, see our guide to filing for divorce in California.
The California K Factor Formula
California’s formula is expressed algebraically as:
CS = K [HN – (H%) (TN)]
Where:
- CS is the child support amount
- K is the K factor, a multiplier that varies based on combined parental income
- HN is the high earner’s net monthly disposable income
- H% is the high earner’s approximate percentage of time with the child
- TN is the total net monthly disposable income of both parents
This formula is too complex to calculate by hand in practical cases. California courts and attorneys use approved software programs to run the calculation. The two most common programs are Dissomaster and XSpouse.
The Role of Dissomaster Software
Dissomaster is a software program developed by The Rutter Group and approved for use in California family courts. It applies the K factor formula and accounts for adjustments such as health insurance, childcare costs, mandatory deductions, and tax filing status. Most California family law attorneys keep a Dissomaster license and run calculations for clients during settlement discussions.
The output from Dissomaster is presented to the court as the presumptive support amount under California Family Code section 4055.
Where to Get Help With Child Support in San Bernardino County
Parents in San Bernardino County have multiple options for child support assistance:
- The San Bernardino County Department of Child Support Services (DCSS) opens and enforces child support cases at no cost to parents. DCSS operates offices in Loma Linda, Ontario, and Victorville and can be reached at (866) 901-3212.
- The San Bernardino Superior Court Family Law Division handles court-ordered child support cases and can be reached at (909) 521-3101.
- The Child Support Division of the San Bernardino Superior Court is located at 655 West Second Street, Second Floor, San Bernardino, California 92415-0248.
Parents who want to fight a child support order or who believe the amount is incorrect should consider hiring a board-certified family law attorney to review the calculation and present arguments for deviation under Family Code section 4057.
What Counts as Income for Child Support
Most states define income broadly. California Family Code section 4058 includes the following as income for child support purposes:
- Salary and wages from all jobs
- Tips, bonuses, and commissions
- Self-employment income (gross receipts minus reasonable business expenses)
- Interest, dividends, and capital gains
- Rental income from real property
- Trust income and distributions
- Disability insurance benefits and workers’ compensation
- Unemployment insurance benefits
- Social Security benefits, except Supplemental Security Income
- Pensions and retirement plan distributions
- Spousal support received from a prior relationship
- Annuities and lottery winnings
- Royalties from intellectual property
Means-tested benefits such as CalWORKs and SNAP food assistance are typically excluded from income. So is Supplemental Security Income (SSI).
How Self Employment Income Is Calculated
For self-employed parents, the court calculates income as gross receipts minus reasonable and necessary business expenses. This is often a flashpoint in contested cases because some parents inflate business expenses to reduce their reported income. Forensic accountants are commonly retained to reconstruct true business income.
Adjustments and Deductions
Once gross income is determined, several mandatory deductions are subtracted to arrive at net disposable income, the figure used in the formula. California Family Code section 4059 lists the mandatory deductions:
- Federal and state income tax actually paid or expected to be paid
- Social Security and Medicare withholdings (FICA)
- Mandatory union dues and retirement contributions
- Health insurance premiums for the parent and any required dependents
- Child support and spousal support previously ordered for other relationships
- Job-related expenses (with limits)
After the guideline support is calculated, the court may add additional support items under California Family Code section 4062. These include:
- Childcare expenses related to employment or job training
- Reasonable uninsured healthcare costs for the children
- Educational expenses or special needs
- Travel expenses for visitation when parents live far apart
Imputation of Income
If a parent is voluntarily unemployed or underemployed, the court can impute income, meaning the court assigns an income amount based on what the parent could be earning. This prevents a high-earning parent from quitting work to avoid child support.
Courts consider several factors before imputing income:
- The parent’s work history and skills
- Available jobs in the area at the parent’s skill level
- The parent’s education and training
- Why the parent is not currently working at full capacity
- Whether the parent has a legitimate reason for reduced earnings, such as care of a disabled child
Imputation is typically supported by a vocational evaluation, which can cost $3,000 to $8,000. Both parents may use vocational experts in contested cases.
How Child Support Is Modified
Child support orders are not permanent. Either parent can request a modification if there has been a material change in circumstances. Common reasons for modification include:
- A significant change in either parent’s income (typically 10 percent or more)
- A change in custody or parenting time
- The child’s needs have changed significantly
- One parent has had additional children with a new partner
- A parent has become disabled or incarcerated
The process to modify support varies by state but typically involves filing a Request for Order or motion in the same court that issued the original order. In California, this is a Request for Order using Judicial Council form FL-300.
Working with an experienced family law attorney can significantly improve the outcome of a modification request, especially when the change involves complex income calculations or contested timeshares.
Enforcement of Child Support Orders
Federal law under 42 U.S.C. section 666 requires every state to maintain a Title IV-D child support agency that enforces child support orders. In California, this function is performed by the California Department of Child Support Services, with county-level offices including the San Bernardino County Department of Child Support Services.
Enforcement tools available when a parent fails to pay child support include:
- Wage garnishment, where support is deducted directly from the paying parent’s paycheck
- Bank account levies
- Interception of federal and state tax refunds
- Suspension of driver’s licenses and professional licenses
- Passport denial or revocation for arrears over $2,500
- Reporting unpaid support to credit bureaus
- Liens against real property
- Contempt of court proceedings, which can result in jail time
These tools work in most cases. However, some parents disappear, work off the books, or move out of state. The Office of Child Support Enforcement, a federal agency, coordinates interstate enforcement when this happens.
Frequently Asked Questions
Q: How much is child support for one child in 2026?
A: Child support for one child averages about 17 to 22 percent of the non-custodial parent’s gross income, though the exact amount depends on state, both parents’ incomes, custody timeshare, and adjustments for health insurance and childcare. For a non-custodial parent earning $5,000 per month, expect roughly $850 to $1,100 monthly for one child as a guideline starting point.
Q: Does child support cover everything a child needs?
A: No. Standard child support covers basic needs such as food, clothing, shelter, and routine expenses. Additional support items such as childcare, health insurance premiums, uninsured medical expenses, private school tuition, extracurricular activities, and travel for visitation are usually addressed separately under California Family Code section 4062 and similar provisions in other states.
Q: How is child support calculated if a parent is self employed?
A: For self-employed parents, the court calculates income as gross business receipts minus reasonable and necessary business expenses. The court will scrutinize deductions and may require tax returns, profit and loss statements, and bank records. Forensic accountants are commonly used in contested cases to reconstruct true income, especially when business expenses appear inflated.
Q: What is the Dissomaster?
A: Dissomaster is a software program approved for use in California family courts to calculate guideline child support. It applies the K factor formula under California Family Code section 4055 and accounts for adjustments such as healthcare premiums, childcare, tax filing status, and mandatory deductions. Both attorneys and judges use Dissomaster to determine the presumptive support amount.
Q: Can I lower my child support if I have less custody time than I want?
A: Child support is calculated based on actual timeshare, not wished-for timeshare. If you want a lower support amount, you must first obtain a higher legal timeshare through a custody modification, then file a support modification reflecting the new schedule. You cannot reduce support based on hoped-for parenting time that has not been ordered or actually exercised.
Q: Does the custodial parent’s income matter for child support?
A: In Income Shares states (including California), yes. The custodial parent’s income is part of the calculation and affects how the total support obligation is divided. In Percentage of Income states (including Texas, Nevada, and Mississippi), the custodial parent’s income generally does not affect the calculation.
Q: What happens to child support if I lose my job?
A: Child support obligations do not automatically stop if you lose your job. You must file a Request for Order (or your state’s equivalent) to modify the support amount based on your reduced income. Until the court issues a new order, the original amount continues to accrue and any unpaid amount becomes arrears. Filing for modification as soon as possible after a job loss is critical.
Q: How long does child support last?
A: In most states, child support continues until the child turns 18 or graduates from high school, whichever happens later. Some states extend support if the child has special needs or is attending college. California ends standard support at age 18 if the child has graduated from high school, or 19 if the child is still a full-time high school student living at home. Some courts may order additional support for disabled adult children.
Bottom Line
Child support calculation seems mathematical but is rarely simple in practice. The formula your state uses (Income Shares, Percentage of Income, or Melson), what counts as income, how timeshare is measured, and what deductions apply all influence the final number. In California, the calculation is governed by Family Code section 4055 and performed using Dissomaster software.
If your child support order does not feel right or your circumstances have changed since the order was issued, a free consultation with a board-certified family law specialist can clarify your options. Many child support calculations contain errors, and modifications are available when circumstances have materially changed.
About the Author
Donald Glen Haslam, Esq. is a Board-Certified Family Law Specialist by the California State Bar Board of Legal Specialization and a senior partner at Haslam & Thorne, LLP in Ontario, California. He has practiced family law exclusively for over 40 years, representing families throughout San Bernardino County and the Inland Empire. Reviewed by Brian George Thorne, Esq., Board-Certified Family Law Specialist.
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Disclaimer: This article is for general informational purposes only and does not constitute legal advice. Child support law is governed by state-specific statutes and varies significantly by jurisdiction. Every family law situation is unique. For advice specific to your circumstances, consult with a licensed family law attorney in your state. Reading this article does not create an attorney-client relationship with Haslam & Thorne, LLP.