Custody Time Calculator

Calculate parenting time percentages for custody schedules.

By Konstantin Iakovlev · Updated September 2026 · Source: California Family Code §4055 — child support formula using parenting time

Parent A

14.25% (52.00 nights)

Parent B

85.75% (313.00 nights)

Custody Breakdown

Parent A Overnights52 nights
Parent B Overnights313 nights
Parent A Percentage14.25%

Use the Custody Time Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only and does not constitute legal advice. Results are estimates based on the information you provide and the rules described on this page. Consult an attorney licensed in your state for advice specific to your situation.

How It Works

Parenting time is usually measured in overnights, and the share each parent holds often drives both child support figures and the language of a custody agreement. For separated or divorced parents trying to make sense of a schedule, putting a clear percentage on that split turns a tangle of calendar dates into something concrete you can discuss or bring to a court.

Behind the percentage is a simple count. Pick a common schedule and the calculator assigns Parent A a fixed number of overnights a year: 52 for every other weekend, 78 for an extended weekend, and 182 for a 5-2-2-5, 2-2-3 or week-on/week-off rotation. Or choose Custom and enter Parent A's overnights yourself. Parent A's share is those overnights divided by 365, and Parent B gets the remaining nights.

Where the numbers go wrong is almost always the exceptions. Holidays, school breaks, and one-off events can swing the final split well away from what the weekly rotation alone suggests, so fold every one of them into your count rather than mapping out only the regular weeks. Review your entries once more before you trust the totals.

Example: 50/50 Custody Schedule (Alternating Weeks)

  1. 1 Input: Week On/Off, which the calculator counts as 182 overnights a year for Parent A; Parent B has the other 183.
  2. 2 Calculation: Parent A = (182 / 365) × 100 = 49.86%. Parent B = (183 / 365) × 100 = 50.14%.
  3. 3 Result: Parent A has 49.86% of the overnights and Parent B 50.14%.
  4. 4 Context: the one-night gap comes from the odd number of days in a year. The calculator always divides by 365, so in a leap year its percentages are off by a fraction of a point. Many child support formulas start from this overnight share, which is why it is worth agreeing on the count before the numbers go into a worksheet.

Source: California Family Code §4055 — child support formula using parenting time · Last updated: September 2026

Frequently Asked Questions

What does 50/50 custody look like?
Common 50/50 schedules include alternating weeks, 2-2-3 rotation (two days with each parent then three with one, alternating), or 3-4-4-3 schedules. The best arrangement depends on the children's ages, school logistics, and parents' work schedules.
How is parenting time percentage calculated?
Count the number of overnights each parent has per year and divide by 365. For example, 182 overnights equals approximately 49.9% parenting time. This percentage often determines child support calculations in most states.
Does custody percentage affect child support?
Yes. In most states, the more time a parent spends with the child, the lower their child support obligation because they are directly providing for the child during that time. Whether a state uses a threshold at all, and where it sits, varies. California, for example, has none: its formula uses the higher earner's share of parenting time directly (Family Code §4055).

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