Parenting Time Percentage Calculator
Calculate parenting time percentage from your overnight schedule.
Returns custody split for sole, primary, and shared arrangements to support legal planning.
Child custody time split calculations convert custody arrangements — expressed as percentages, fractions, or day counts — into concrete schedules. Courts and parents use these calculations to determine overnights per year, child support obligations, and compliance with custody orders.
Percentage split formula: Parent A % = (Parent A Overnights ÷ Total Overnights per Year) × 100
Overnights from percentage: Overnights = (Custody % ÷ 100) × 365
Standard custody schedule equivalents:
- 50/50 split: 182.5 overnights each
- 60/40 split: 219 / 146 overnights
- 70/30 split: 255 / 110 overnights
- 80/20 split: 292 / 73 overnights (every other weekend)
- 90/10 split: 328 / 37 overnights
Child support adjustment — income shares model: Most US states use the Income Shares model, where custody percentage affects the non-custodial parent’s support obligation: Support Adjustment = Base Support × Overnight Adjustment Factor
The more overnights the non-custodial parent has, the lower the support obligation (because direct costs shift to that parent during their parenting time).
Common schedule patterns:
- Week on/week off: exactly 50/50 (52 weeks each)
- 2-2-3 rotation: 50/50 with frequent transitions
- Every other weekend: ~14% time (52 overnights/year) for non-custodial parent
- Every other weekend + one weeknight: ~20% (73 overnights/year)
Worked example: Parents agree on a “2-2-5-5” schedule: child spends 2 days with Parent A, 2 days with Parent B, then 5 days with Parent A, 5 days with Parent B (repeating 14-day cycle).
- Parent A days in cycle: 2 + 5 = 7 out of 14
- Parent A annual overnights: (7 ÷ 14) × 365 = 182.5 overnights (50%)
- Parent B annual overnights: 182.5 overnights (50%)
This is a true 50/50 schedule despite not being a simple week-on/week-off arrangement.