Montana Child Support Calculator — 2026 Estimate

How Montana Calculates Child Support

Montana is one of only three states that uses the Melson formula for child support. Delaware and Hawaii are the others. Montana's child support guidelines are established under Montana Code Annotated Section 40-4-204 and the Montana Child Support Guidelines Rules. The Melson formula operates on a principle that most people find fundamentally fair: a parent must first be able to meet their own basic needs before being required to contribute to their children's support above a baseline level.

Montana uses net income as its starting point. Net income means income after subtracting taxes and mandatory payroll deductions. Montana's state income tax uses progressive rates ranging from 4.7 percent to 5.9 percent depending on income and filing status in 2026.

The Montana Melson Formula: Three Steps

Step 1: Establish Each Parent's Self-Support Reserve

Before any support is calculated, Montana identifies how much each parent needs for their own basic living expenses. This is called the Self-Support Reserve (SSR). Montana sets the SSR at a level that reflects the cost of basic necessities for a single adult in the state.

To calculate available income: start with gross monthly income. Subtract Montana state income taxes at the applicable rate. Subtract federal income taxes based on filing status and withholding. Subtract Social Security at 6.2 percent of wages up to $176,100 annually in 2026. Subtract Medicare at 1.45 percent of all wages. Subtract mandatory union dues if applicable. The result is net monthly income. Then subtract the SSR. The remaining figure is that parent's available income for child support purposes.

A parent whose net income falls at or below the SSR may be ordered to pay only a minimal or token amount. The formula does not push any parent below their own basic needs threshold to fund child support.

Step 2: Calculate the Children's Primary Support

Montana sets a per-child monthly Primary Support amount representing the cost of each child's basic needs: food, clothing, shelter, and essential care. Both parents contribute proportionally to the Primary Support based on their available income after the SSR deduction.

An example: Parent A has $1,800 in available income. Parent B has $900. Combined available income is $2,700. Parent A's share is 66.7 percent. If Montana's Primary Support amount for one child is $500 per month, Parent A contributes $333 and Parent B contributes $167. When Parent A has less parenting time, Parent A pays Parent B $333 as the base obligation before Step 3.

Step 3: Standard of Living Adjustment

After the children's basic needs are funded, Montana applies the Standard of Living Adjustment (SOLA). The SOLA allows children to share in a higher standard of living when either parent has income above what basic expenses require.

The SOLA is a percentage of the paying parent's remaining net income after the SSR and Primary Support obligations are deducted. Montana's SOLA percentage is established in the state guidelines. A paying parent with substantial income above the basic threshold will have a meaningful SOLA. A paying parent with income just above the SSR will have a minimal or zero SOLA. The SOLA is added to the Primary Support amount to produce the total monthly child support payment.

What Counts as Income in Montana

Montana courts include wages, salaries, commissions, bonuses, overtime, self-employment income, rental income, pension and retirement distributions, Social Security benefits, SSDI payments, unemployment compensation, and workers' compensation.

Courts can impute income to a parent who is voluntarily unemployed or underemployed based on work history, education, and local employment conditions. Montana excludes needs-based public assistance from the income calculation. SSDI and Social Security retirement benefits count as income.

Step-by-Step: How to Use This Calculator

Step 1. Calculate your net monthly income. Subtract Montana state income taxes, federal taxes, Social Security, and Medicare from your gross income.

Step 2. Note the Self-Support Reserve. The calculator applies the current Montana SSR automatically and subtracts it to show your available income.

Step 3. Calculate the other parent's net monthly income and available income using the same process.

Step 4. Enter the number of children to set the Primary Support amount used in Step 2.

Step 5. Enter your parenting time percentage. Count overnights per year and divide by 365.

Step 6. Add healthcare costs. Enter the monthly premium for the children's health insurance.

Step 7. Review all three steps in the breakdown. The calculator shows the SSR deduction, Primary Support allocation, and SOLA component separately. Each line explains a distinct part of the calculation.

Parenting Time Adjustments in Montana

Montana adjusts the child support obligation when the paying parent has significant parenting time. A parent spending more time with their children directly covers more of their daily needs during that time. Courts reflect this through an adjustment to the calculated obligation. At near-equal parenting time, the SOLA component may also be reduced because both parents are actively spending directly on the children.

Montana courts have discretion to adjust the formula result when the parenting arrangement differs substantially from the standard assumption built into the guidelines.

Add-On Expenses in Montana

Healthcare premiums and work-related childcare costs are allocated proportionally based on each parent's available income within the formula. Extraordinary medical costs and other necessary child-specific expenses may be added at the court's discretion and split proportionally.

Reading Your Results

Your results show gross income for both parents, net income after deductions, the SSR deduction for each parent, available income, the Primary Support allocation, the SOLA component, and the total monthly obligation.

Pay close attention to the available income figure. If one parent's net income is close to the SSR, their obligation will be small even if their gross income looks meaningful by comparison. This is the Melson formula working as designed.

After You Get Your Estimate

Montana courts follow the Melson formula as established in the Montana Child Support Guidelines Rules. Deviation is available when the result would be inequitable given specific circumstances. Courts consider both parents' full financial situations, the children's actual needs, and any factors that make the standard result unfair.

Montana also permits a review every two years on request. Either parent can ask for a recalculation after two years without needing to prove a specific material change in circumstances. If income has shifted meaningfully since the last order, this two-year review right gives both parents a regular opportunity to update an order that no longer reflects current reality.

A licensed Montana family law attorney familiar with the Melson formula can walk through your specific numbers. Most offer a free first consultation.

How Montana calculates child support

Montana uses the Melson Formula — a more detailed version of the income shares model used only by Delaware, Hawaii, and Montana. The Melson Formula prioritizes ensuring both parents can meet their own basic needs before calculating how much support the children receive.

How the Melson Formula works

First, each parent is entitled to keep a self-support reserve — enough income to cover their own basic living needs. Only income above that reserve is available for child support calculations. Next, a primary support need per child is established. Both parents contribute to that minimum proportionally. Any remaining income above the primary need is then shared with the children through a Standard of Living Adjustment (SOLA).

Important note

The Melson Formula is significantly more complex than other models. The estimate shown above is a simplified approximation. For accurate results in Montana, use Montana's official child support worksheet or consult a family law attorney.