Custody Calculator
Child support worksheets, mediation sessions, and court forms all ask the same question in the same format: what percentage of the year does the child spend with each parent? Guessing that number, or repeating a schedule’s nickname like “every other weekend” as if it were a percentage, is where support figures start to drift.
This calculator turns your actual schedule into both parents’ percentages, from annual overnights or from weekly hours, names the type of arrangement the split represents, and includes the common schedule presets so you do not have to count 52 weekends by hand. It is a planning aid, not legal advice: it documents a schedule, it does not decide one.
Planning aid only. Custody percentages affect child support differently by state and country; confirm with a family-law professional before filing anything. This page is general information, not legal advice for your situation.
Quick Answer
Key takeaways
- Count overnights for a full year, holidays and vacations included, then divide by the year’s total. A named schedule is a starting estimate, never the filed number.
- Use the hours method only when care genuinely has no overnights, such as infant care or daytime-only time. Never mix an overnight count for one parent with an hours count for the other.
- The percentage feeds child support worksheets and tax rules: according to IRS Publication 504, the custodial parent for tax purposes is generally the one the child lived with for the greater number of nights.
- The arrangement label here describes the time split only. Courts decide plans on the child’s best interests, not on which side of a percentage line a schedule falls.
How to use the custody calculator
Start with the method that matches your family. Choose Annual overnights if your child sleeps at each parent’s home on a rotating schedule, which covers most school-age arrangements. Either type both parents’ overnight counts, leave auto-fill on and type one count (the other is completed to 365), or pick a preset to see what a named schedule is really worth before adjusting it for your holidays and vacations. Choose Weekly hours if the child’s time is built from daytime care without sleepovers, and enter each parent’s hours of care in a typical week, out of 168.
Add the parents’ names only if you want them printed on a result you copy for a mediator, a co-parenting discussion, or your own records. Then calculate and read three things: the two percentages, the share bars, and the arrangement type. If the split surprises you, the usual cause is uncounted holiday and vacation time, so recount with a calendar open before you treat the number as final. Parents working through the wider separation paperwork may also need the cost side of the process, covered by the California divorce calculator for that state’s filing and fee structure.
The formula, and what the arrangement labels actually mean
Those labels are this calculator’s plain-language summary of the split, and they follow the thresholds worksheets commonly use: near-equal time reads as joint, a clear majority over 60 percent reads as one primary home, and the band between reads as shared but uneven. They are not legal categories in your state or province, and the same 55/45 split can be called joint physical custody in one jurisdiction and shared parenting in another. What travels across jurisdictions is the percentage itself, which is why getting the count right matters more than the label attached to it.
One counting warning that decides real cases: be consistent about what an overnight is. The California Courts self-help guidance on preparing a custody and parenting time agreement frames a parenting plan around where children live and when they see each parent, day by day, including holidays and vacations. Count from that full calendar, the same way for both parents, rather than from the two-week rotation alone.
Worked examples: overnights and hours
The calculator is pre-filled with the overnights example, and every figure below is what it returns.
| Method | Inputs | Parent 1 | Parent 2 | Arrangement type |
|---|---|---|---|---|
| Overnights | 200 and 165 nights of 365 | 54.8% | 45.2% | Shared/Joint (50/50) |
| Weekly hours | 60 and 108 hours of 168 | 35.7% | 64.3% | Primary Physical (Parent 2) |
The hours example shows why method choice matters. A parent providing 60 hours of care a week, perhaps every weekday daytime while the child sleeps at the other home, holds 35.7 percent of the week’s hours but zero overnights. On an overnights worksheet that parent would record 0 percent, which is precisely why states that deal with infant and daytime-heavy schedules allow hours-based counting, and why the two methods must never be blended in one filing.
Common schedules converted to percentages
These are the calculator’s own presets, stated for Parent 1 in a 365-day year, before holiday and vacation adjustments. Use them as a first estimate, then replace them with your counted totals.
| Schedule | Overnights | Share of the year | Typical label at that share |
|---|---|---|---|
| Every other weekend (Fri-Sun) | 52 | 14.2% | Primary Physical (other parent) |
| Every other weekend, extended (Fri-Mon) | 78 | 21.4% | Primary Physical (other parent) |
| Every other weekend plus one weeknight | 104 | 28.5% | Primary Physical (other parent) |
| 4-3 split (60/40) | 156 | 42.7% | Shared/Joint (50/50) band |
| Week on / week off, or 2-2-3 | 183 | 50.1% | Shared/Joint (50/50) |
The gap between the first row and most parents’ intuition is the lesson of this table. “Every other weekend” sounds like a quarter of a child’s life; counted honestly, it is about a seventh of the year, and it only reaches the high 20s once a weekly overnight is added. Summer blocks move these numbers materially: four extra weeks in summer add roughly 28 overnights, about 7.7 points, to the weekend parent’s share.
What competing custody calculators miss
Miss 1: one counting method only. Most parenting-time tools reviewed for this page accept overnights and nothing else, which silently scores daytime-only care at zero. This calculator’s hours mode exists for exactly the families those tools fail: infants, split days, and shift-based care.
Miss 2: no presets, so the counting burden lands on stressed parents. Hand-counting a year of weekends during a separation is error-prone. The presets convert the five common schedules instantly, and this page’s table shows the same conversions in print so the figures can be checked without touching the tool.
Miss 3: a percentage with no context about what it changes. Bare tools rarely explain that the number feeds support worksheets, shared-parenting thresholds such as the 40 percent line in Canada’s Federal Child Support Guidelines step-by-step guide, or tax rules keyed to nights. This page connects the number to those uses while stating plainly, in the calculator itself, that it is a planning aid and not a legal determination.
One honest limit: this calculator counts time only. It does not calculate child support, apply any state’s worksheet, or weigh the best-interests factors a court must consider, which the Child Welfare Information Gateway’s state summaries, such as its Florida best-interests summary, show can run to a dozen or more factors. Your percentage is one input to that process, never the outcome.
Frequently Asked Questions
In many US states the percentage is a direct input to the child support worksheet: as one parent’s share of overnights rises, that parent is treated as covering more of the child’s day-to-day costs, and support is adjusted, sometimes only after a threshold such as 20 or 40 percent is crossed. Canada’s Federal Child Support Guidelines similarly change the approach once each parent has the child at least 40 percent of the time. The percentage alone never sets the amount, because income and expenses also feed the formula, so treat your result as an input to your jurisdiction’s official worksheet, not as a support figure.
Generally, a night the child sleeps at that parent’s home, or a 24-hour period of care where overnights do not apply. Definitions vary by court and by worksheet, and some orders count a day with a late-evening return differently from a sleepover. Whatever definition your order or local guidance uses, apply it the same way to both parents, and count from the actual calendar rather than from the schedule’s nickname.
Use overnights for school-age children on standard rotating schedules; most US state guidelines are written in overnights. Use hours when care is mostly daytime without sleepovers, for example with infants, split school days, or a parent whose time is built around work shifts. Do not mix the two in one calculation: a percentage built from overnights and a percentage built from hours describe the same year differently and are not interchangeable on a worksheet.
Add them to the annual counts before you calculate. A two-week summer vacation block is about 14 overnights, roughly 4 percentage points of the year, and alternating holidays can add several more. Parents who calculate from the school-term schedule alone routinely understate the other parent’s time by 3 to 6 points, which is exactly the range where support adjustments and shared-parenting thresholds often sit.
A leap year has 366 overnights instead of 365. In this calculator, turn the auto-fill option off and enter both parents’ actual overnights so they total 366; the percentages then divide by 366 automatically. The auto-fill shortcut always completes the year to 365. The difference is small, under 0.2 percentage points for most schedules, but using 366 keeps a leap-year count exact.
Because the hours method divides each parent’s hours by the full 168 hours in a week, not by the hours the two of you entered. If you enter 60 and 108 hours, they cover the whole week and the shares add to 100 percent. If you enter hours that total less than 168, perhaps because school hours were left out, the shares will add to less than 100 percent, and the gap is the unassigned time. Decide together who is responsible for school and sleep hours before comparing results.
No to both. The label in this calculator is a description of the time split, not a legal outcome. Courts decide parenting plans on the child’s best interests, weighing stability, schooling, each parent’s availability, distance between homes, and safety, and they can approve or reject a 50/50 plan on those grounds. Child support also does not automatically become zero at equal time, because incomes usually differ and most guidelines still order a payment from the higher earner.
No. It is a planning aid that turns a schedule into percentages, using the counting methods courts and worksheets commonly use. It does not interpret your court order, predict what a judge will do, or replace your jurisdiction’s official child support worksheet. Custody and support rules differ sharply by state, province, and country, so confirm any number you plan to file or rely on with a family-law professional or your court’s self-help service.
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References
- California Courts Self-Help Guide, “Ask for or change a custody and parenting time order” – the official step-by-step for requesting or changing custody and parenting time orders in California. California Courts: Ask for a Custody Order. Accessed October 2026.
- California Courts Self-Help Guide, “Prepare a custody and visitation (parenting time) agreement” – what a parenting plan must cover: legal custody, physical custody, and the day-by-day time schedule including holidays and vacations. California Courts: Prepare a Parenting Time Agreement. Accessed October 2026.
- California Courts, “What to expect from family court mediation” – how mediation builds parenting plans around children’s best interests and continuing contact with both parents. California Courts: Family Court Mediation. Accessed October 2026.
- Child Welfare Information Gateway, “Determining the Best Interests of the Child: Florida” – the statutory best-interests factors Florida courts weigh, including stability, schooling, and continuity of care. Child Welfare Information Gateway: Florida. Accessed October 2026.
- Child Welfare Information Gateway, “Determining the Best Interests of the Child: South Carolina” – South Carolina’s custody factors, including each parent’s capacity to meet the child’s needs and encouragement of the other parent’s relationship. Child Welfare Information Gateway: South Carolina. Accessed October 2026.
- Child Welfare Information Gateway, “Determining the Best Interests of the Child: Oregon” – Oregon’s factors under Rev. Stat. 107.137, including emotional ties and willingness to encourage a continuing relationship with the other parent. Child Welfare Information Gateway: Oregon. Accessed October 2026.
- Child Welfare Information Gateway, “Determining the Best Interests of the Child: Wisconsin” – Wisconsin’s best-interests considerations, including the child’s wishes and the stability of the proposed arrangement. Child Welfare Information Gateway: Wisconsin. Accessed October 2026.
- Internal Revenue Service, “Publication 504: Divorced or Separated Individuals” – the custodial-parent definition based on the greater number of nights, Form 8332 releases, and the tiebreaker rules for claiming a child. IRS: Publication 504. Accessed October 2026.
- Internal Revenue Service, “Dependents” FAQ – why a child is a dependent of only one taxpayer per year, and how the special rule for divorced or separated parents applies. IRS: Dependents FAQ. Accessed October 2026.
- Department of Justice Canada, “The Federal Child Support Guidelines: Step-by-Step” – how split and shared parenting time, including the 40 percent shared-time threshold, changes the support calculation. Justice Canada: Child Support Guidelines. Accessed October 2026.
- Department of Justice Canada, “Child Support in Canada” research summary – the three US support models (percentage of income, income shares, and the Melson formula) and how shared physical custody adjusts obligations. Justice Canada: Child Support Models. Accessed October 2026.