How 50/50 Custody Changes Child Support, State by State

Parents often assume equal time means no support changes hands. In most states that is wrong. When incomes differ, most formulas still move money from the higher earner to the lower earner at 50/50, just less than they would with a standard schedule.

What actually varies is the mechanism. Some states have no parenting time formula at all. Some flip a switch at a set overnight count. Some slide continuously with every overnight. The same 182 or 183 nights can mean three very different calculations depending on where your case sits.

One number to know before reading on: courts count overnights per year, not hours or days. A year has 365 of them, and an exact half is 182.5, so true 50/50 orders usually alternate 182 and 183.

New York’s statute has no shared-custody formula. Its courts filled the gap: the Child Support Standards Act percentages apply even in shared custody (Bast v. Rossoff, 91 N.Y.2d 723 (1998)), and with truly equal time the higher-earning parent is treated as the noncustodial parent and pays the full guideline amount (Baraby v. Baraby, 250 A.D.2d 201 (3d Dep’t 1998)).

A court can deviate using the statutory factors, but the starting point at 50/50 in New York is the same 17 to 35 percent calculation as any other case. Of the 51 states this site covers in depth, it is the one where equal time changes the math the least.

Florida, North Carolina, and Illinois all use a version of the same shared-care math, but each opens the door at a different overnight count. Florida triggers at 73 overnights, 20 percent of the year. North Carolina requires each parent to hold at least 123 overnights. Illinois requires 146 overnights each.

Once past the threshold, all three run the cross-multiplication: the basic obligation is multiplied by 1.5 to reflect the cost of two full households, each parent’s share is weighted by the other parent’s percentage of overnights, and the two results are offset so the parent owing more pays the difference.

Ohio takes a lighter touch. At 90 or more court-ordered overnights the obligor automatically gets a 10 percent reduction, and at 147 or more the court must either grant a further deviation or explain why not. There is no full offset formula.

Threshold designs create cliff effects. In Illinois, moving from 145 to 146 overnights changes the entire formula, which is why overnight counts get litigated. Our schedule tools show exactly how many overnights any pattern produces.

Pennsylvania works in percentage points. When the obligor’s custody share reaches 40 percent of overnights, their income share of the obligation drops by the amount their custody share exceeds 30 percent. At exactly 50/50, ten points come off, and a special rule applies: support runs only from the higher earner, capped at the amount that equalizes the parties’ net incomes.

Georgia, effective January 1, 2026, replaced its old discretionary deviation with a formulaic parenting time adjustment driven by each parent’s court-ordered days raised to the power 2.5. Michigan has used that curve for years: its parental time offset weighs each parent’s support obligation by the other parent’s overnights to the 2.5 power, so every added overnight nudges the transfer smoothly instead of jumping at a cliff.

Texas sits at the other extreme: no formulaic overnight adjustment exists. Possession time is one discretionary deviation factor among many, and the guideline percentage applies to the noncustodial parent regardless of a near-equal schedule unless a court finds reason to vary.

Run any offset formula with identical incomes and identical overnights and it returns zero, because each parent’s claim cancels the other’s. Introduce an income gap and money flows again, even at a perfect 182.5-night split. The formulas are built to equalize what the child experiences in each home, not to reward a particular schedule.

That is worth knowing before bargaining over two overnights a month. Sometimes they change the support number a lot, sometimes not at all. The state pages linked above each show the exact mechanics with a worked example, and the calculators let you test your own numbers at different overnight counts.