How to Calculate Children's Timeshare with Each Parent in California

If you're figuring out child support in California, one of the first numbers you need is your timeshare percentage — the share of time each parent spends with your children across the year. It sounds simple, but the math trips up a lot of parents, and an inaccurate number can mean hundreds or even thousands of dollars in support payments set at the wrong level. This guide walks you through how to calculate timeshare, what the most common schedules look like in percentage terms, and how California's updated 2024 child support formula treats parenting time.

What is timeshare and why does it matter?

Timeshare is the term California courts use for the percentage of time each parent has primary physical responsibility for the children. Courts sometimes call this the "custody percentage," and in the child support formula it's referred to as the "H% factor" (for the high-earning parent's share). Whatever the label, it measures the same thing: what fraction of the year does each parent actually have the kids?

The reason timeshare matters so much is that California uses it as a central variable in its guideline child support formula. The parent who has the children for more time tends to shoulder more of the day-to-day costs of raising them, so the formula reduces their obligation accordingly. A parent with very little time is usually ordered to pay more. Even a small shift in the schedule — say, adding one overnight per week — can meaningfully move the support number, sometimes by hundreds of dollars per month.

For this reason, it's important to be precise when you report parenting time to the court. Courts consider regular weekday and weekend time, as well as holidays, vacations, and school breaks. If your schedule varies throughout the year, courts calculate an average annual timeshare rather than relying on what happens in a typical week.

How to calculate your timeshare percentage

The most accurate method is an hours-based calculation. There are 8,760 hours in a standard year. Count the total hours the lower-time parent has the children across all of the regular schedule, holidays, vacations, and school breaks, then divide that total by 8,760 and multiply by 100 to get a percentage.

Some counties measure timeshare by overnights rather than hours. In those jurisdictions, the count is simpler: total the noncustodial parent's overnight stays per year and divide by 365. The two methods usually produce slightly different numbers for the same schedule, which is why it's worth knowing which approach your county uses before you file. Orange County, for example, specifies that parenting time is typically measured by the number of overnights each parent has in a year; other counties default to an hours calculation. When in doubt, an hours-based count is more precise and is the method the California state guideline calculator supports.

If you don't want to do the math by hand, the California Department of Child Support Services offers the official state guideline calculator, which includes an "Advanced Timeshare" feature. You enter your specific schedule details and it calculates the percentage automatically.

One important note: don't count holiday time twice. If a parent gets the kids every other weekend plus Christmas break, the Christmas time replaces the regular alternating weekend, it doesn't add to it. Duplicating days is one of the most common errors in DIY timeshare calculations.

California timeshare chart: common schedules and percentages

The chart below shows the timeshare percentage for the lower-time parent under several of the most common California parenting schedules. "Alternate" means every other week. These figures reflect time with the children excluding holidays and special days unless otherwise noted; adding holiday time will increase the percentage.

If your schedule isn't listed, you can still find your percentage using the formula described in the previous section. The key is to be thorough: count every block of time across a full 12-month period, including school breaks, summer vacation, and rotating holidays.

How the 2024 child support law update affects timeshare

California made its first major revision to the statewide child support guidelines since 1992 when Senate Bill 343 (SB 343) took effect on September 1, 2024. The changes don't alter how timeshare is calculated, but they do change how timeshare interacts with the formula in several important ways:

• Updated K-factor brackets. The K-factor is the portion of combined parental income allocated to child support. SB 343 recalibrated the income bands and K-factor multipliers for the first time in more than 30 years. Depending on your combined income level, support amounts may be higher, lower, or roughly the same as under the prior rules.
• Add-ons are now split proportionally. Previously, childcare and uninsured medical costs were typically split 50/50. Under SB 343, those add-on expenses are now divided in proportion to each parent's net income by default. If one parent earns significantly more, they'll pay a larger share.
• Broader income definition. SB 343 expanded what counts as income, adding capital gains, severance pay, non-need-based veterans' benefits, and military housing and food allowances. More income sources in the calculation can affect the final support amount even when timeshare stays the same.
• Low-income protections strengthened. If the paying parent's income falls below the threshold set by full-time minimum wage work, a rebuttable presumption kicks in for a lower support amount. The threshold is now recalculated annually based on the current California minimum wage.
• DissoMaster is no longer certified. The longtime standard calculation software stopped renewing its certification and stopped updating its tax tables. As of January 2025, DissoMaster produces incorrect results. Courts now use certified alternatives such as Xspouse or Family Law Software.

The bottom line: if you have an existing child support order that predates September 2024, it was calculated under the old formula. If your circumstances have changed or you simply want to know whether recalculation would benefit your family, it's worth running the numbers again using a current, certified calculator.

What to do once you have your percentage

Once you've calculated your timeshare, the next step is plugging it into the child support formula along with both parents' net monthly incomes. The official California guideline calculator at childsupport.ca.gov will do that math for you and give you a support estimate. Keep in mind that the result is an estimate — the judge or commissioner makes the final determination, and local rules (including how certain counties round timeshare percentages) can affect the outcome.

If you and your co-parent are negotiating a parenting plan, understanding the timeshare percentages for different schedules can help you both see the financial implications of various arrangements before anyone files paperwork. That kind of transparent conversation tends to make agreements stick. You might find it helpful to review what courts look for when evaluating parenting arrangements for minor children before you start drafting your plan.

Once you have an agreed parenting schedule and a support number, Hello Divorce can help you turn those agreements into a complete, court-ready parenting plan and settlement agreement. You don't need to hire a full-service attorney to get this right. See our plans to find the level of support that fits your situation.

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