Child Custody Time-Share Calculator
Calculate parenting time-share percentage based on overnights per year — the standard input most states use to determine custodial parent status and child support adjustments.
| School year overnights (180 nights) | — |
| Summer overnights | — |
| Holiday overnights | — |
| Total overnights / year | — |
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.
Last updated May 2026. Sources: California Dissomaster Guide, Texas Family Code Ch. 154.