Idaho Child Support Calculator

Idaho calculates child support from both parents’ combined gross income using the brackets in Idaho Rule of Family Law 120: a set percentage of the first $10,000 of combined annual income, a lower percentage of the next $10,000, and so on up to $440,000. The total is split between the parents by income share. When each parent has the children more than 25% of overnights, Idaho multiplies the basic amount by 1.5 and offsets the parents’ shares. The calculator below uses the schedule as amended effective July 1, 2025.

Before taxes, minus child support or maintenance you pay under other court orders (Rule 120(e)-(f)).
More than 25% (92 or more) for each parent triggers the shared custody formula.
Add-on costs (monthly, optional)
Compare your order with what the guideline produces today.

How Idaho calculates child support

Idaho uses an income shares guideline: both parents support the children in proportion to their incomes. The steps under Rule 120:

  1. Find each parent’s Guidelines Income. This is gross income before taxes from almost any source, including wages, bonuses, self-employment profit, Social Security, unemployment, disability and veterans’ benefits, plus significant employment perks such as a company car or free housing. Court-ordered child support and spousal maintenance paid for another relationship are deducted.
  2. Add the two incomes and convert to an annual figure.
  3. Apply the bracket percentages for the number of children. For two children, for example, the rule takes 26% of the first $10,000, 25% of the next $10,000, 23% of the next $10,000, and continues at falling rates.
  4. Divide the result by each parent’s share of combined income. The parent with 25% or less of the overnights pays their share to the other parent.

Rule 120 gives its own example: parents earning $25,000 and $10,000 a year with two children have $35,000 combined. The brackets produce about $709 a month, and the higher earner’s 71% share is about $506 a month. The calculator reproduces that result.

The 25% shared custody rule

Idaho recognizes that shared custody raises the total cost of raising children. If the children spend more than 25% of overnights in a year with each parent (92 or more), the rule adjusts the calculation:

  • The basic child support amount is multiplied by 1.5.
  • That figure is multiplied by each parent’s percentage of income.
  • Each result is multiplied by the percentage of overnights the children spend with the other parent.
  • The two amounts are offset, and the parent owing more pays the difference.

A parent never pays more under the shared formula than they would if the children lived entirely with the other parent. If the calculation leaves a parent who has more than half the overnights paying support, that parent can argue it is inappropriate using the factors in Rule 120(i)(7). Parenting time is counted by overnights in a calendar year: every other weekend from Friday to Sunday, for example, is 52 overnights, or about 14%.

Child care and health insurance

Basic child support does not cover work-related child care. The court may order the parents to share reasonable work-related child care costs in proportion to income, usually paid directly between them. Health insurance should be provided by the parent who can get appropriate employer coverage at lower cost, and premiums and uncovered medical costs are shared. Any single uncovered expense that would cost the other parent more than $500 for a course of treatment needs advance written approval or a court order. The calculator shows the child care and insurance split as a separate line rather than folding it into the monthly support figure.

Low and high incomes

Idaho says support should rarely be set at zero. There is a rebuttable presumption of at least $50 per child per month. When the paying parent earns under $800 a month, the court should review both parents’ incomes and living expenses so the order does not leave the paying parent below a minimum subsistence level.

At the top, the schedule runs to $440,000 of combined annual income. Support on the first $440,000 is calculated under the guidelines. Above that, the court can order more after considering the child’s resources and needs, both parents’ finances, the standard of living during the marriage and any special needs or talents.

When the court can set a different amount

The guideline amount can be adjusted when evidence shows it is inappropriate. If the court departs from it, it must state on the record what the guidelines would have produced and the circumstances that justify the difference. Income can also be imputed: a parent who is voluntarily unemployed or underemployed can be charged with what they could earn, but incarceration is not treated as voluntary unemployment.

Changing an existing Idaho order

A change in the guideline amount can itself be a substantial and material change of circumstances that supports a motion to modify. Changes in income, custody time or health insurance coverage are common reasons. Under Idaho Code § 32-709, a modification applies only to payments that come due after the motion is filed, so file promptly. Enter your current order in the calculator to see how far it sits from today’s guideline.

The full modification process for Idaho and every other state is in Navigating Child Support. Our forms app prepares the court paperwork from your answers, and the free modification audit checks whether your order is worth revisiting. Other states are in the 50-state child support calculator.

Frequently asked questions

Does Idaho use gross or net income for child support?

Gross income, before taxes, minus support and maintenance paid under other court orders.

How many overnights is shared custody in Idaho?

More than 25% of the year with each parent, which is 92 or more overnights.

What is the minimum child support in Idaho?

Rule 120 presumes at least $50 per child per month, subject to the paying parent’s ability to meet basic living needs.

When did Idaho’s child support schedule last change?

Rule 120 was amended effective July 1, 2025. The calculator uses the amended brackets.

Sources

This page and calculator provide general legal information, not legal advice. Child support rules change and the court decides the final amount. For advice about your situation, consult a licensed Idaho attorney.