How to Calculate Custody Percentage

Some state courts calculate parenting time based on the number of overnights your child spends with you each year. Others calculate it by hours. Either way, it affects the amount of child support the court orders you to pay at the time of your divorce, as well as later child support modifications.

Calculating Child Support

When parents divorce, most states calculate child support based on a formula called the income shares model. The formula sets aside a portion of both parents’ combined incomes for their children’s financial needs, such as food and shelter. Both parents are responsible for paying a percentage of that portion, based on the percentage they contribute to their combined income total. For example, if Dad earns 65 percent of the parents’ combined incomes, and if he is the non-custodial parent, he would pay child support equal to 65 percent of the portion the court allots to the children. The custodial parent contributes her percentage by paying the child’s expenses directly. But this is a base number, and it assumes that his child never spends any time with the non-custodial parent. Courts make further calculations after arriving at this figure.

Importance of Custody Percentage

When parents divorce, courts determine a parenting plan first, then calculate child support, because support is based on the projected amount of time a child will spend with each parent per year. The law acknowledges that when a non-custodial parent has his child with him, he is paying direct expenses on her behalf during those times. Therefore, the more time his child spends with him, the more it whittles away at the base child support amount. This saves him from paying twice -- once to the custodial parent through child support, and again for direct costs when his child is living with him.

Overnight Custody Calculations

Some states, such as New Jersey and Nevada, calculate custody percentages by overnights. If you live in one of these jurisdictions, you can figure your time by counting the number of nights your child spends with you each year, based on the custody terms of your decree. Half-days don't count. If your child spends Friday and Saturday nights at your home every other weekend, this comes out to 52 overnights a year, or two nights times 26 weeks. If you divide 52 by 365, the number of nights in a year, your custody percentage is 14 percent. If your child also sleeps at your house every Wednesday night, this adds an additional 52 nights to the equation and increases your time to 104 nights a year. Your custody percentage increases to 28 percent. When the court calculates your child support obligation, you would receive credit for paying your child’s costs of living 28 percent of the time.

Hourly Custody Calculations

Some states, such as California, use a more detailed approach to calculate a parent's percentage of custodial time. These states calculate your custody percentage by dividing the total number of hours your child spends with you each year by 8,760, the number of hours in a year. This works out to 29 percent if your child spends every other weekend with you and one week night every week, based on a standard pick-up and drop-off time of 5:00 PM. Even though the visitation schedule is the same, calculating time this way works out to an additional 1 percent over the course of a year.

Support Modifications

If you spend a lot of extra time with your child, in addition to the time provided for in the custody terms of your decree, you might find that it adds up, especially if your state calculates custody percentages by hours. This won’t affect your child support obligation in your divorce decree, because the court will calculate your support based on your projected time with your child. But if you find that you spend significantly more time with her than what’s included in your decree, and if you document it over a period of time, consult with an attorney about going back to court and asking a judge to recalculate your support based on these new numbers.