Child support is one of the most confused areas in family law. People search the internet for a formula, get a generic number, and walk into court with an estimate that has nothing to do with the model the court actually applies. The LawSensai Child Support Calculator runs your state's actual model on your actual inputs.
This post walks through the five models in use across the United States, which states use which, and how to read the calculator output.
What the Child Support Calculator does
The calculator takes the inputs the state's official model requires and runs the same math the court will run. The output is a guideline amount under the state model with the inputs you provided. The output is a calculation, not an order. Courts can deviate from guideline amounts in limited circumstances, but the guideline is where the conversation starts in every jurisdiction.
The calculator covers all 50 states and the District of Columbia. Each state's implementation matches the current official model.
The five models in use
There are five distinct child support models used across the United States.
Income Shares. The model most states use. It combines both parents' incomes, applies a schedule that estimates what an intact family at that combined income would spend on the children, and allocates the obligation proportionally to each parent's share of combined income. The model treats child support as a shared obligation and adjusts for the parenting time split.
Percentage of Income. A simpler model used in a small number of states. It applies a percentage to the obligor parent's income based on the number of children. The model does not directly account for the other parent's income.
Melson. A more complex model developed in Delaware. It applies a primary support obligation, reserves a self-support amount for each parent, and adds a standard of living adjustment when the obligor's income permits. Delaware, Hawaii, and Montana use the Melson model.
Obligor-Only. A variant of the Percentage of Income approach. North Dakota uses this model.
Tax-Adjusted. California's model. It accounts for the parties' tax positions and is based on a complex statutory formula commonly known as the K factor formula.
The calculator routes to the correct model based on the state of the matter. You do not pick the model. The state's law picks it.
Which state uses which model
The model assignment for each state matches the official guidelines on the relevant state agency website. The calculator is anchored to the current published guidelines. When a state updates its schedule or its formula, the calculator picks up the change.
Most states use the Income Shares model. Percentage of Income remains in use in a small group of states. Melson runs in Delaware, Hawaii, and Montana. Obligor-Only runs in North Dakota. California runs the Tax-Adjusted formula.
The calculator surfaces the model name with the result so you can see which model was applied and look it up against the state's official guidance if you want to verify.
What inputs the calculator asks for
The inputs depend on the model. Across models, the standard inputs include:
Gross monthly income for each parent. The calculator surfaces the state-specific definition of income, which can include wages, self-employment income, investment income, and in some states overtime and bonuses.
Number of children supported by this order.
Health insurance premiums paid for the children.
Childcare costs incurred to allow either parent to work.
Other child support orders the obligor parent is paying.
Parenting time split or overnight count, which most models use to adjust the obligation.
State-specific deductions and adjustments, which vary by model.
The calculator marks the state-specific fields so you know when an input is a quirk of your state's model and not a standard input.
How to read the output
The output shows the guideline amount, the model that was applied, the inputs that drove the calculation, and the adjustments that were made. You see which parent is the obligor under the calculation and the periodic amount.
The calculator also runs sensitivity. If you adjust an input within a reasonable range, you can see how the guideline number moves. Sensitivity matters because income inputs are often approximate at the start of a family law matter and the parties want to know how robust the calculation is.
Using the calculator as a mediation anchor
The Family Law mediation tools use the calculator as an anchor. When a party proposes a support number, the mediation surface shows the proposal next to the calculated guideline. This is the calculator anchor pattern that prevents proposals from drifting from the math. The proposal can still differ from the guideline. The party making the proposal owns the reason for the difference.
Spanish language support
The calculator runs in Spanish. The input labels, the model names, and the output explanation are localized.
Common misreads we see new users make
Misread one: thinking the calculator output is the order. It is not. The court enters the order. The guideline is the starting point. Courts can deviate within their rules and the calculator does not predict deviations.
Misread two: comparing the output to a number from a different state's calculator. The models differ. A guideline number in California is not comparable to a guideline number in Texas because the models compute differently. Compare your state's number to your state's guideline.
Misread three: entering net income instead of gross. Most state models start with gross income and apply deductions inside the model. Entering net at the top double-counts the deductions and produces a number lower than the real guideline.
Practical next steps
Step one: start a calculation at lawsens.ai/calculator/child-support. Pick the state of the matter.
Step two: enter the inputs the state model asks for. The calculator marks which fields are state-specific.
Step three: save the result to your matter at lawsens.ai/matters/[id] so the mediation surface and the Settlement Composer can use it as the anchor for any support discussion.
How the Child Support Calculator connects to the rest of LawSensai
The calculator is the math engine that anchors every support-related conversation inside LawSensai. The mediation surface uses it as the calculator anchor. The Settlement Composer pulls the calculated number into the support section of the draft agreement. The Document Vault stores the income documentation that the calculation was based on. Aggregate calculator usage and safety findings are published at lawsens.ai/trust/family.
This post is informational and is not legal advice. Final child support orders are entered by a court. Use the calculator to understand the guideline. Use an attorney to address deviations.
Read more
- lawsens.ai/product/child-support-calculator
- lawsens.ai/trust/family
- lawsens.ai/help/income-definition
- lawsens.ai/help/state-models
- lawsens.ai/product/family-mediation
- U.S. Department of Health and Human Services Office of Child Support Services overview at acf.hhs.gov
Last verified: 2026-04-09.