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 turn an arrangement into concrete numbers, whether it was agreed as a percentage, a fraction, or a pattern of days. Courts and parents use the result to set overnights per year, child support obligations, and compliance with a custody order.
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
- 90/10 split: 328 / 37 overnights
Why the overnight count drives child support
Most US states use the Income Shares model, where the parenting time split feeds directly into the non-custodial parent’s support obligation. The more overnights that parent has, the lower the obligation, because direct costs shift to them during their own parenting time.
This calculator does not compute a support figure, and no honest calculator can from an overnight count alone. Every state has its own formula, its own income tables and its own threshold, and several change the arithmetic abruptly at a specific number of overnights rather than sliding smoothly. Common thresholds sit around 92 overnights (25%), 110 (30%) and the equal-parenting line at 182.5 (50%), but the one that matters is the one in your own state’s guidelines.
What the overnight count does tell you is which side of those lines you are on, which is usually the whole argument. Get the number right first, then look up what your state does with it.
Common schedule patterns:
| Pattern | Overnights/year | Share |
|---|---|---|
| Week on / week off | 182.5 | 50% |
| 5-2-2-5 and 3-4-4-3 rotations | 182.5 | 50% |
| Every other weekend + one weeknight | 104 | 28.5% |
| Every other weekend, Fri–Sun | 52 | 14.2% |
Count the overnights before you argue about the label. “Every other weekend” sounds like a meaningful share of the year and is 14% of it. Adding a single midweek overnight every week doubles that to 28.5%, and in states that adjust child support at a 25% or 30% overnight threshold, one weeknight is the whole argument.
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.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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