How Do I Calculate Child Support for Multiple Children in Washington?

Support for two or three children is not simply the one-child figure multiplied out. Washington uses a single economic table that already accounts for how many children an order covers.

Start With the Economic Table

Child support in Washington begins with a statewide chart called the economic table. You find the row that matches the parents' combined monthly net income, then read across to the column for the number of children the order covers. That number is the basic support obligation for the whole family, and it is the starting point before any other costs are added.

The table is built into state law at RCW 26.19.020. It has separate columns for one, two, three, four, and five children. Reading down the correct column matters, because the table does not assume that each additional child costs the same as the first. The per-child amount generally decreases as the number of children rises, which reflects the reality that households share many costs. That is why calculating support for three children is not the one-child number tripled. It is a distinct figure the table already sets.

What Changed on January 1, 2026

If you are calculating support in 2026, use the current version of the table. Effective January 1, 2026, RCW 26.19.020 was updated so that the economic table is presumptive for combined monthly net incomes up to and including $50,000 per month. Under the prior version, the table topped out at a presumptive figure for combined monthly net income of twelve thousand dollars. The updated table extends the chart well beyond that ceiling before the court's discretion to exceed the presumptive amount comes into play. For most families the practical mechanics are unchanged, but for higher-income households the 2026 update means the table itself now supplies a presumptive number across a much wider range of incomes.

Figuring Out Combined Monthly Net Income

Because the table is driven by combined monthly net income, getting that number right is the heart of the calculation. Each parent starts with gross income from essentially all sources, then subtracts the deductions the law allows, such as taxes, mandatory retirement contributions, and certain other items, to reach net income. The two parents' net incomes are added together to find the combined figure, and that total points you to the correct row on the table.

Getting income right is where many do-it-yourself calculations go wrong. Overtime, bonuses, self-employment income, and second jobs can all factor in, and the deductions are specific rather than open-ended. Small errors in income ripple through the entire result, so it is worth being careful and honest about the inputs.

Splitting the Obligation Between the Parents

Once the table gives you the basic support obligation for all the children, that amount is divided between the parents in proportion to their incomes. State law directs that the basic support obligation derived from the economic table is allocated between the parents based on each parent's share of the combined monthly net income. This rule appears in RCW 26.19.080.

In practice, if one parent earns sixty percent of the combined net income, that parent is generally responsible for sixty percent of the basic obligation, and the other parent for forty percent. The parent the children live with most of the time typically receives the transfer payment, since that parent is presumed to be meeting their share directly through daily care.

Do the Children's Ages Change the Number

A common question is whether older children automatically produce a higher support figure. Under the current Washington economic table in RCW 26.19.020, the columns are organized by the number of children and the combined income level, not by an automatic age bracket that raises the amount. The direct driver of the basic obligation is how many children the order covers and what the parents earn together, not a built-in age multiplier.

That said, a child's age and specific needs can still influence the overall order in other ways. The law allows the court to consider factors like larger families and special needs when setting the final amount, including whether to adjust the result in a particular case. Those considerations live in the standards at RCW 26.19.065, which address the limits and adjustments a court weighs rather than a fixed age surcharge. If you have seen references to an old age-based split in the schedule, be careful, because the older separate age provision in the schedule was repealed years ago and is no longer the governing rule.

Adding the Costs That Sit Outside the Table

The table figure is only the basic obligation. On top of it, the parents share certain other costs in the same income-based proportion, including health care, day care, and special child-rearing expenses. Those add-ons are governed by RCW 26.19.080 and are calculated separately from the basic number. So a full support picture for two or three children is the table amount, split by income, plus each parent's proportional share of these additional expenses.

A Snohomish County Reality Check

Parents in Snohomish County file their worksheets in the Superior Court in Everett, and the same statewide table and rules apply here as everywhere in Washington. The most common trouble spots are not the table itself but the income figures and the add-on expenses, which is exactly where a careful review pays off.

Get the Numbers Right the First Time

Calculating support for multiple children involves more moving parts than a single number, and errors in income or in the add-on expenses can follow a family for years. The Law Office of Chad Foster helps parents throughout Snohomish County build accurate child support worksheets and understand what the result should be. Reach out to schedule a conversation about your family's numbers.