Child Support Guidelines Calculator
Tuesday morning in family court somewhere in West Tennessee. A pro se parent is at the table. She pulls out a printed worksheet she ran the night before. Every line cites the rule. She hands it to the judge. The judge nods.
The problem
A presumptive child-support number drives every divorce, paternity, and modification case in this country — millions per year. The state's official PDF will not compute. The .gov worksheet has no math behind it. The lawyer across the room uses a paid commercial calculator that does not show its work. The pro se parent has no defensible alternative, so she agrees to the wrong number.
Most legal-tech aimed at pro se users patronizes them. Most commercial calculators are closed-source, citation-free, and priced to keep aid organizations out. There is no reason a citation-backed, open-source, free-PDF, no-login calculator should not exist for all fifty states. Before this build, none did.
The harness
Two states live. Tennessee — Tenn. Comp. R. & Regs. ch. 1240-02-04, income-shares reference engine, AOC-style filing-ready PDF. Mississippi — Miss. Code Ann. § 43-19-101/-103, statutory-percentage reference, CS-101/102 structure, plus the Deviation Reconciliation Engine that tracks each statutory factor (a–l), captures side-by-side obligor/obligee positions, runs chancellor decision sweeps (adopt obligor / adopt obligee / split / reject), and produces a printable Deviation Memo with Behind-the-Scenes HTML and Sensitivity HTML alongside it.
Every computed line carries the controlling subsection — 1240-02-04-.04(6)(b) on the page, in the PDF, in the cite-to-rule overlay. Pure TypeScript. Zero I/O. Runs in the browser. Ships at the edge on Cloudflare Workers. CI-enforced Vitest fixtures lock the math in place — every PR ships a fixture and a citation. MIT licensed. Repo at github.com/tcbmem-png/csg_tcblaw. No login. No paywall. No analytics that profile the litigant.
The result
The parent prints the worksheet the night before court. The number is defensible. The judge reads it. The legal aid worker embeds the link in her self-help resource page. The family-law attorney with a hearing tomorrow produces the right number with the right citation faster than the official form. Two of fifty states. Forty-eight to go.
The next ship is the Quarterly State Champion Briefing — once a quarter, every active certifying attorney gets a real briefing. What changed in the rules. What landed in the engine. What needs review before next quarter. One ask. The long arc moves CSG off tcblaw.org to a neutral nonprofit umbrella, recruits state champions one jurisdiction at a time, and earns the federal-level recognition that locks in long-term legitimacy.