Child Custody Time-Share Calculator

Time-share percentage is the share of overnights each parent has with the children annually. It's the standard input that family courts and child-support calculators use to adjust support amounts — and the higher your time-share, the lower your support obligation in most states.

How Time-Share Is Counted

Most states count overnight stays (where the child sleeps), not waking hours. A parent with the child from 8am Saturday until 7pm Sunday has one overnight, not two. School-year overnights are computed from the parenting plan (e.g., every other weekend = 2 overnights per 14-day cycle = 52 nights/year over 36 school weeks).

Time-Share Thresholds by State

California: full support adjustment above 30% time-share via Dissomaster. Texas: ~50% threshold for split custody adjustment. Illinois: 40% threshold for shared parenting modification. Florida: 73 overnights (20%) triggers credit. Each state has its own formula; this calculator gives you the input — your local guidelines do the math.

Document Your Time

Use a co-parenting app (OurFamilyWizard, TalkingParents, Custody X Change) to log actual overnights. Courts give weight to consistently exercised time-share. If your parenting plan grants you 40% but you only actually take 25%, expect support to be calculated on the actual exercised time.

Overnights Per Year for Common Parenting Schedules

Before you negotiate, know what each standard schedule actually produces over a full year. Every other weekend (Fri–Sun) gives the non-residential parent 2 overnights per 14 days, about 52 nights or 14.3%. Every other weekend plus one midweek overnight reaches roughly 78 nights or 21.4% — which is what pushes a Florida parent past the 73-overnight credit threshold. Extended alternate weekends (Thu–Mon) reach about 104 nights or 28.6%, just under California's 30% adjustment point. 5-2-2-5, 2-2-3, and week on / week off all produce 182 or 183 nights, an even 50%. Summer and holiday blocks are added on top of the school-year cycle, and they are usually what moves a schedule across a threshold — four extra summer weeks alone is 28 overnights, or 7.7 percentage points. Enter each block separately in the calculator above rather than estimating a single annual percentage, because the thresholds below are decided by the exact overnight count, not by a rounded figure.

Why the Exact Overnight Count Matters More Than the Percentage

Several states apply their support adjustment at a hard cutoff rather than on a sliding scale, so a single overnight either side of the line can change the annual support figure by a meaningful amount. Florida's statute grants substantial time-sharing treatment at 73 overnights — at 72 the standard formula applies, at 73 the alternate one does. That is why courts and support software count nights rather than accept a percentage: 20% of 365 is 73.0, and rounding a schedule described as “about 20%” can land on the wrong side. Two further points routinely catch parents out. First, courts generally calculate on the time actually exercised, not the time granted — a plan awarding 40% that you exercise at 25% will usually be recalculated at 25%. Second, leap years contain 366 days, so a 50/50 schedule gives one parent 183 nights and the other 183, but an odd-numbered schedule shifts by a night. Verify your state's threshold and its rounding rule with the state guideline itself before relying on any calculator, this one included.

Last updated 2026-08-12. Sources: California Courts self-help — child support, Texas Family Code Ch. 154, Florida Statutes § 61.30 (73-overnight substantial time-sharing threshold).