How this calculator works
Tennessee child support is calculated by following a specific sequence of steps set out in Rule 1240-02-04. The calculator implements those steps exactly. This page walks through them in plain English.
The big picture
Tennessee uses the Income Shares Model. The idea: children should receive the same proportion of parental income that they would have received if the parents lived together. The calculator works in three phases:
- Establish the baseline — combine the parents' income, find the Basic Child Support Obligation (BCSO).
- Allocate between parents — split the BCSO by each parent's percentage of combined income.
- Adjust for circumstances — parenting time, add-ons, deviations.
The Box 5 trap
If you're using a W-2, you must use Box 5 (Medicare wages), not Box 1. Box 1 is net of voluntary 401(k) / 403(b) contributions — the Guidelines don't permit deducting those. For high earners, the difference can change the final obligation by hundreds of dollars per month.
The three income zones
- SSR zone (very low income obligor): A Self-Support Reserve check applies — the lower of pro-rata BCSO or obligor-only BCSO is used.
- Schedule zone (combined AGI ~$1,200 to $28,250): Direct lookup from the BCSO Schedule, rounded UP to the next $50.
- Above-cap zone (over $28,250): Top-of-schedule plus a percentage of the excess (6.81% / 7.22% / 7.77% / 8.05% / 8.66% by number of children). The 4-child rate is 8.05%, not the 8.25% some third-party sources state.
50/50 parenting
For equal parenting (182.5 days each), the rule designates one parent as the ARP solely for purposes of the adjustment, and the variable multiplier becomes exactly 2.0. The algebra reduces to:
Net support = BCSO × |PI_A − PI_B| Direction: higher-earning parent → lower-earning parent
Per Rule .04(7)(f), when the PRP-by-designation actually earns more than the ARP-by-designation, support flows from PRP to ARP.
Add-ons vs. deviations
Add-ons (health insurance premium for the children, recurring uninsured medical, work-related childcare) are mandatory and allocated pro-rata to income share.
Private school is a discretionary deviation — not a mandatory add-on. The court must make written findings that the deviation is in the child's best interest and consistent with the parents' finances. If granted, it is allocated pro-rata.
Special expenses (camp, lessons, travel, school clubs) have a unique 7% threshold: only amounts exceeding 7% of monthly BCSO are considered as a deviation, unless the parties agree to waive the threshold.
High-income cases — the four protections
Tennessee's guidelines contain four distinct mechanisms that shape outcomes when one or both parents are high earners. These often get conflated; they serve different functions and operate at different points in the calculation.
Layer 1 — The schedule cap ($28,250/mo combined AGI)
The official BCSO schedule ends at $28,250 combined monthly AGI. This is not a cap on support — it's the cap on the lookup table. Above it, Rule .09(2)(d) applies an above-cap formula: top-of-schedule BCSO plus a per-child percentage of the excess AGI (6.81% / 7.22% / 7.77% / 8.05% / 8.66% for 1–5 children). There is no upper bound on BCSO under this formula.
Layer 2 — The statutory presumptive cap (burden shift)
Tenn. Code Ann. § 36-5-101(e)(1)(B) sets a per-child threshold: $2,100 (1) · $3,200 (2) · $4,100 (3) · $4,600 (4) · $5,000 (5+). When the calculated PCSO exceeds the threshold, the parent receiving support has the burden to prove by preponderance of the evidence that the excess is reasonably necessary for the children's needs. This is a rebuttable presumption, not a hard cap. Modest excesses are routinely approved with brief findings; substantial excesses face real scrutiny.
Layer 3 — The "actual needs" standard (case law)
How "reasonably necessary" gets evaluated under Layer 2 comes from case law: Hugger v. Hugger (Tenn. Ct. App. 1999), Smith v. Smith(Tenn. Ct. App. 2007), and Nash v. Mulle, 846 S.W.2d 803 (Tenn. 1993). Courts look to the children's documented needs, their pre-divorce standard of living, and other contributions the obligor is already making — not just the obligor's ability to pay.
Layer 4 — The 50/50 cross-credit mechanic (structural)
In 50/50 cases, presumptive support depends on the difference in parental income shares, not the absolute level. Two high earners with similar incomes pay near-zero presumptive support, regardless of how high combined AGI is — the model assumes each can independently provide a comparable lifestyle. See Rule .04(7)(b)(2)(i).
Worked example
Parent A $65,000/mo, Parent B $20,000/mo, 3 children, 50/50 custody, A pays $300/mo health.
- Combined AGI $85,000 → above the schedule cap, so Layer 1 engages.
- BCSO = $2,954 + ($56,750 × 7.77%) = $7,363
- PI: A 76.5%, B 23.5%. 50/50 net = $7,363 × 53% = $3,902 (A→B)
- Add A's share of premium → PCSO ≈ $4,128
- Statutory cap (3 kids) = $4,100 → excess $28 — trivial, easily justified.
- Change to standard parenting and the same incomes produce PCSO ≈ $5,862 — excess $1,762, a real settlement lever.
- Change to two equal $42,500/mo earners on 50/50 and presumptive support drops to ~$0 — Layer 4 doing the work.
Five worked examples
These stories illustrate how the Income Shares model and the high-income protections operate across the meaningful permutations of income disparity and custody. Every PCSO below has been verified against this site's calculation engine on the 2022 DHS schedule (effective Oct 1, 2021). Where a number differs from a back-of-envelope estimate you may have seen elsewhere, the "How our engine handles it" coda explains why. Child support only — alimony (T.C.A. §36-5-121) is a separate analysis and is not addressed here.
| Story | Combined AGI | Split | Custody | PCSO | Above stat. cap? | Key protection |
|---|---|---|---|---|---|---|
| 1 | $20,000/mo | 100/0 | Standard | $2,197 | No | None needed |
| 2a | $85,000/mo | 76.5/23.5 | Standard | $5,560 | +$1,460 | Statutory cap + case law |
| 2b | $85,000/mo | 76.5/23.5 | 50/50 | $3,827 | No | Cross-credit |
| 3 | $72,000/mo | 69.4/30.6 | 50/50 | $2,166 | No | Cross-credit |
| 4 | $68,000/mo | 51.5/48.5 | 50/50 | $745 | No | Cross-credit |
| 5 | $125,000/mo | 80/20 | Standard | $8,257 | +$4,157 | Statutory cap + case law (heavily) |
Story 1 — The single-earner case
Facts: Parent A $20,000/mo, Parent B $0 (stay-at-home), 2 children, standard parenting (A is ARP at 80 days), A pays $400/mo children's health premium.
Calculation: Combined AGI $20,000 is below the $28,250 schedule cap. BCSO from the 2022 schedule (2 children, $20,000 AGI rounded up) = $2,197. PI is 100/0, so A's pro-rata share = $2,197. Health premium reimbursement flows through Rule .04(8) at B's 0% share — i.e., nothing flows. PCSO = $2,197/mo, plus A continues paying the $400 premium directly.
Protections: Schedule cap not engaged (below cap). Statutory cap not engaged ($2,197 < $3,200 for 2 children). 50/50 cross-credit not applicable.
Strategic note: If the facts were reversed — non-earning parent becomes the ARP — Rule .04(7)(f) permits PRP→ARP support, but only if the pro-rata math produces a positive number. With $0 income for the ARP, it doesn't. A non-earning ARP may end up with no entitlement; counsel for a lower-earning spouse should weigh this when negotiating the parenting plan.
How our engine handles it
Our BCSO table is the 2022 DHS schedule (effective Oct 1, 2021), the version currently in force. Some older write-ups cite $2,374 here — that's the 2017 schedule. The engine rounds combined AGI up to the next $50 schedule line per Rule .09(2)(c), then looks up the column for the number of children. With PI 100/0, every downstream pro-rata calculation collapses to "A pays it all," which is exactly what the schedule line says.
Citations: Rule 1240-02-04-.09 (BCSO Schedule); Rule .04(7); Rule .04(8); Rule .07(2)(d).
Story 2 — High earner / moderate earner (standard vs. 50/50)
Facts: Parent A $65,000/mo, Parent B $20,000/mo, 3 children. A pays $300/mo health premium. A pays $5,000/mo private school directly under a parenting-plan provision (handled outside the order per Rule .04(8), like Story 4). Two custody scenarios.
BCSO (above-cap): $2,954 + ($56,750 × 7.77%) = $7,363. PI: A 76.5% / B 23.5%.
2a — Standard parenting (A is ARP): A's pro-rata BCSO = $5,631. Net health add-on: B owes A B's 23.5% share = $71/mo (reduces A's outflow). PCSO = $5,560. Statutory cap (3 kids) = $4,100, so excess $1,460/mo ($17,520/yr) — substantial. Recipient bears the Hugger / Smith / Nash burden to show actual need. A's counter: "$4,100 + $5,000 direct private school = $9,100/mo already going to the kids."
2b — 50/50 parenting: Cross-credit = $7,363 × |76.5%−23.5%| = $3,898. Less B's pro-rata health reimbursement to A ($71). PCSO = $3,827. Below the $4,100 cap. The custody choice alone moves the order by ~$1,733/mo.
How our engine handles it
Two pieces of mechanics drive these numbers, and both trip people up:
- Above-cap BCSO. Once combined AGI clears $28,250, the engine switches from a table lookup to the Rule .09(2)(d) formula:
top_of_schedule + excess_AGI × per-child rate. The 3-child rate is 7.77%. Bumping AGI by another $1,000 raises BCSO by $77.70 — linear, with no upper bound. - Add-on reimbursement direction. When the obligor pays the premium directly, the worksheet does not add it on top of their obligation. The non-paying parent owes their pro-rata share back to the payer. The engine implements this as a signed adjustment from A's perspective: paid by A → negative (reduces A's outflow); paid by B → positive (increases A's outflow). Some narratives accidentally double-count by both adding the premium and netting the reimbursement; we don't.
- Private school choice. If you toggle private school into the order in the calculator (Rule .07(2)(d) deviation), the engine pro-rates it the same way — B would owe A about $1,176/mo of B's share, dropping 2a's PCSO to ~$4,384. We've left it outside the order here because the facts say A pays directly.
Citations: Rule .09(2)(d); §36-5-101(e)(1)(B); Rule .04(7)(b)(2)(i); Rule .04(8); Rule .07(2)(d).
Story 3 — Two high earners with significant disparity
Facts: Parent A $50,000/mo (surgeon), Parent B $22,000/mo (hospital-employed physician), 2 children, 50/50 parenting, A pays $500/mo children's health premium.
BCSO (above-cap): $2,803 + ($43,750 × 7.22%) = $5,962. PI: A 69.4% / B 30.6%. Cross-credit = $5,962 × 38.8% = $2,318. Less B's pro-rata health reimbursement to A: $500 × 30.6% = $153. PCSO = $2,166/mo (A→B).
Protections: Schedule cap engaged; statutory cap not engaged ($2,166 < $3,200). Cross-credit is doing the work — without 50/50, A's pro-rata BCSO would be ~$4,138 and a similar order would land near $4,000.
Counter-intuitive takeaway: The order here is smaller in absolute terms than Story 2, despite a comparable combined income. The model doesn't redistribute wealth between two adequately-resourced households; it equalizes the children's experience between them.
How our engine handles it
For "equal" parenting the engine designates Parent B as the ARP at 182.5 days per Rule .04(7)(b)(2)(i), runs the standard variable-multiplier formula, and the algebra collapses to BCSO × |PI_A − PI_B|. We expose this in the result panel as the 50/50 cross-credit. Then add-ons are applied as signed pro-rata flows: when A pays the premium, B owes A B's share, so the net is −$153 from A's outflow. The engine never adds the premium itself to A's obligation — that's already coming out of A's pocket.
Citations: Rule .09(2)(d); Rule .04(7)(b)(2)(i); Rule .04(8); §36-5-101(e)(1)(B).
Story 4 — Two high earners with near-parity
Facts: Parent A $35,000/mo, Parent B $33,000/mo (both partners at different law firms), 2 children, 50/50. A pays $400/mo health; B pays $1,500/mo work-related childcare; $4,000/mo private school split 50/50 directly by agreement (outside the order per Rule .04(8)).
BCSO (above-cap): $2,803 + ($39,750 × 7.22%) = $5,673. PI: 51.5 / 48.5. Cross-credit = $5,673 × 3.0% = only $167.
Add-ons drive the total: Pro-rata childcare A owes B = $1,500 × 51.5% = $772. Net health: B owes A $400 × 48.5% = $194 (reduces A's outflow). Net add-on = +$578 to A. PCSO = $745/mo (A→B).
Limit case: At exactly equal incomes ($34,000/$34,000) with 50/50 and no add-ons, the cross-credit produces $0. That's not a bug — it's the model recognizing that two identical households need no equalization.
How our engine handles it
This story exercises every direction of the add-on logic at once: a premium paid by the higher earner (net flow back to A) and childcare paid by the lower earner (net flow from A). The engine carries each add-on as a signed amount from A's perspective and sums them, which is why a $578/mo add-on swing can dwarf a $167/mo presumptive cross-credit. When you set "private school paid by split_pro_rata" the engine zeroes that flow entirely — recognizing that the parents are handling it directly per Rule .04(8). And the zero-presumptive limit case is the cleanest illustration in the whole engine of why 50/50 with parity produces a structural floor.
Citations: Rule .09(2)(d); Rule .04(7)(b)(2)(i); Rule .04(8); Rule .04(7)(f).
Story 5 — The ultra-high-income case
Facts: Parent A $100,000/mo (investment banker), Parent B $25,000/mo (corporate counsel), 3 children, standard parenting (A is ARP). A pays $600/mo health, $9,000/mo private school, $3,000/mo activities/tutoring — all directly under the parenting plan (outside the order per Rule .04(8)).
Mechanical calculation: Combined AGI $125,000. BCSO = $2,954 + ($96,750 × 7.77%) = $10,471. A's pro-rata (80%) = $8,377. Less B's pro-rata health reimbursement to A: $600 × 20% = $120. Mechanical PCSO = $8,257/mo ($99,084/yr).
Statutory cap: $4,100 for 3 children. Excess $4,157/mo ($49,884/yr) — very substantial. Recipient bears the Hugger / Smith / Nash burden to document actual needs beyond what A's $12,600/mo in direct contributions already covers.
Likely outcomes (highly fact-dependent):
- Court approves $8,257 with detailed findings — rare without extraordinary documented needs.
- Court caps at $4,100 plus documented deviations (e.g., college savings) — common.
- Court approves something in between based on a balancing of evidence — most common in contested cases.
Discretionary trusts: §36-5-101(e)(1)(B) authorizes the court to direct above-threshold amounts into a 529, college savings account, or trust for the children's benefit — protecting the function of the support without redirecting it to the recipient parent's cash flow. Worth proposing proactively.
How our engine handles it
The engine doesn't "cap" anything on its own — Tennessee's statutory presumption is rebuttable, so producing a hard cap would be wrong. Instead, when the calculated PCSO exceeds the §36-5-101(e)(1)(B) threshold, the engine sets pcsoExceedsStatutoryMax = true and emits a neutral cap note in the result panel and the PDF, including: the calculated PCSO, the cap, the dollar/annual excess, a severity label tied to the size of the excess (here: "very substantial — detailed evidentiary record of the children's actual needs is typically required"), and the Hugger / Smith / Nash citations. It then surfaces a side-by-side panel so counsel can see calculated vs. cap vs. excess at a glance. The order amount the user sees is still the mechanical $8,257; the judge does the rebuttable-presumption work, and the engine equips both sides to make that argument.
Citations: Rule .09(2)(d); T.C.A. §36-5-101(e)(1)(B); Hugger v. Hugger (Tenn. Ct. App. 1999); Smith v. Smith (Tenn. Ct. App. 2007); Nash v. Mulle, 846 S.W.2d 803 (Tenn. 1993).
What these stories illustrate together
- The mechanical formula has no upper bound, but the law does. The above-cap formula would produce roughly $35,000/mo for a couple at $500K/mo combined AGI. The statutory cap and Hugger line exist to prevent absurd outcomes.
- Custody arrangement matters as much as income. Stories 2a and 2b have identical incomes and produce $5,560 vs. $3,827 — a $1,733/mo swing driven purely by the parenting schedule.
- Income parity creates structural protection. Stories 3 and 4 produce moderate or minimal support at very high combined incomes. The model doesn't redistribute wealth between similarly-situated providers.
- The statutory cap protects the higher earner; case law shapes how it operates. Trivial excesses are routinely approved; substantial excesses require real evidence.
Scope note: These stories address child support only. In cases involving alimony under T.C.A. §36-5-121, the analyses must be integrated — a high-income obligor's total support obligation can exceed the sum of either calculation in isolation, and the "extreme economic hardship" deviation under Rule .07 may come into play. Consult a licensed Tennessee attorney.
Lifecycle
This calculator produces a single-point-in-time snapshot. The obligation will change when a child ages out, private school tuition changes, health insurance changes, or either parent's income changes materially (a 15% variance triggers a modification right under T.C.A. § 36-5-101(g)). A well-drafted MDA should anticipate these triggers.