Child Support Calculators & Guides by Jurisdiction
Child support is the most formula-driven part of family law — and the formulas are different in every jurisdiction. Texas uses a percentage of one parent's net resources. California uses an algebraic guideline with a timeshare factor. New York uses a percentage of combined income with a cap. Illinois uses a dollar schedule table. The UK uses percentages of gross weekly income with shared-care bands. Canada uses province-by-province tables. Australia and New Zealand use income-shares formulas with different care-cost tables. This hub links to every child support page on the site, and explains which pages are calculators and which are guides — and why.
Calculators (working tools)
- Texas — percentage of obligor's net resources; $11,700/month cap from 1 September 2025; low-income rates under $1,000.
- California — CS = K[HN − (H%)(TN)] with the September 2024 K-table and multi-child multipliers.
- New York — CSSA percentages of combined income; $193,000 cap from 1 March 2026; support to age 21.
- UK — CMS — paying-parent percentages of gross weekly income; £3,000/week cap (2012 scheme); nights-band reductions; £39 default rate.
Guides (method + checked examples, no invented calculator)
- Illinois — income-shares schedule (2025 values); 146-night shared-care rule now, 110 nights from 1 January 2027.
- Canada — federal tables (2025, from 1 October 2025); Ontario example; Quebec uses its own model.
- Australia & New Zealand — income-shares formulas with different care-cost tables, never interchanged.
How the models differ
| Jurisdiction | Model | What drives the figure |
|---|---|---|
| Texas | Percentage, obligor only | Obligor's net resources; other parent's income is a deviation factor only |
| California | Algebraic guideline | Both parents' net disposable income and the high earner's timeshare |
| New York | Percentage of combined income | Combined income up to the cap, split pro rata |
| Illinois | Income shares, schedule table | Combined net income looked up in the HFS schedule |
| UK | Percentage of gross weekly income | Paying parent's gross weekly income and shared-care nights |
| Canada | Province tables | Paying parent's guideline income and province of residence |
| Australia / NZ | Income shares | Each parent's income share minus cost share, on different care tables |
Long-tail questions these pages answer
Generic “child support calculator” pages are well covered by government tools and large legal sites. These pages are built for the specific questions people actually ask once they know the basics: child support above the cap in Texas, how California's timeshare factor changes the result, why New York has no shared-custody offset, the Illinois maintenance and schedule changes coming in 2026 and 2027, and how UK shared-care nights reduce a CMS amount band by band. If your question is not answered here, the methodology page explains what research is planned next.
Frequently asked questions
These questions are shown on the page in full. They are not marked up as FAQ structured data.
Why do some jurisdictions have guides instead of calculators?
Where the law uses a schedule table, a discretionary factor, or a computed allowance rather than a simple formula, a calculator would have to invent precision. Those pages show the method and a checked example instead.
Are these figures court orders?
No. Every figure is an estimate only — not legal advice and not a court order. Courts can deviate on the facts of a case.
Related
Other pages for the same jurisdiction or the same topic: