Methodology
Every calculator on this site is a direct implementation of a statute or an official guideline. This page explains where the numbers come from, what we assume when we estimate taxes, how we test the formulas, and what the tools do not do.
Last updated
Where each formula comes from
We start from the primary source: the section of the state code that sets the guideline, plus the schedule or chart it references. For child support that is Texas Family Code chapter 154, California Family Code sections 4050 to 4076, section 61.30 of the Florida Statutes, New York Domestic Relations Law section 240(1-b), 750 ILCS 5/505 with the Illinois HFS schedule, Pennsylvania Rules of Civil Procedure 1910.16-1 to 1910.16-7, chapter 26.19 RCW in Washington, chapter DCF 150 of the Wisconsin Administrative Code, chapter 425 of the Nevada Administrative Code, and section 20-108.2 of the Code of Virginia. For alimony it is Texas Family Code chapter 8, California Family Code sections 3600 and 4320 to 4339 together with county temporary support guidelines, section 61.08 of the Florida Statutes, New York Domestic Relations Law section 236(B), 750 ILCS 5/504, Pa.R.Civ.P. 1910.16-4, and Virginia Code section 16.1-278.17:1.
Each calculator page links to the exact sections it relies on, and the result panel lists every intermediate figure so you can check the arithmetic against the statute yourself.
How we estimate net income
Most guidelines run on net income, but families usually know their gross pay. When you enter gross income, we estimate taxes the same way state agencies build their own conversion charts: a single filer taking the standard deduction, with Social Security and Medicare withheld. The 2026 federal assumptions are:
| Item | 2026 figure |
|---|---|
| Standard deduction, single | $16,100 |
| Income tax brackets, single | 10% to $12,400; 12% to $50,400; 22% to $105,700; 24% to $201,775; 32% to $256,225; 35% to $640,600; 37% above |
| Social Security tax | 6.2% of wages up to $184,500 |
| Medicare tax | 1.45%, plus 0.9% above $200,000 |
| Self-employment | 15.3% on 92.35% of net earnings, with half deducted before income tax |
California estimates also withhold state income tax at the latest published Franchise Tax Board brackets and State Disability Insurance. Illinois applies its 4.95% flat tax after the personal exemption and Pennsylvania its 3.07% flat tax, in both cases without local taxes. New York deducts FICA and, when you mark a parent as a city resident, New York City income tax, because that is what the CSSA allows. Texas, Florida, Washington and Nevada have no state income tax on wages, and Virginia, Wisconsin and Nevada guidelines run on gross income, so no tax estimate is needed there. If you already have a net figure from a worksheet, enter it directly and no tax estimate is applied.
Testing
Every formula is covered by automated tests that compare its output with worked examples derived from the statute: the Texas cap and multiple-family table, the California K factor across income bands, the Florida schedule rows and the 1.5 gross-up, the New York cap and self-support reserve, and each alimony ceiling. The tests run before any change is published. We also encourage you to reproduce the result in your state's official calculator or worksheet; each page links to it.
Review dates and updates
Each calculator page shows the date its figures were last reviewed. We re-check federal tax numbers every January when the IRS and Social Security Administration publish them, the New York caps every March of even-numbered years, the Texas cap on its six-year cycle, and every state whenever its legislature amends the guideline. State-specific tax tables are refreshed when the agency publishes them.
What the calculators do not do
- They do not apply deviation factors. Judges can and do depart from the guideline with findings.
- They do not impute income to a parent who is unemployed or underemployed, which courts may do.
- They estimate taxes for a single filer; head-of-household status, itemized deductions and credits change net income.
- They do not apply California's low-income adjustment or hardship deductions, or county-specific local rules beyond those noted.
- They are not the official calculator of any state agency and cannot be filed with a court.
Corrections
If you believe a figure is wrong, send the statute section and the input values to the address on the contact page. We review reports within a week and record the fix in the page's review date. Our editorial policy describes how content is sourced and reviewed.