Parenting Time Percentage Calculator

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.