How Michigan calculates child support
Michigan does not leave child support to a judge's instinct. Every order starts from the Michigan Child Support Formula (MCSF), a manual published by the State Court Administrative Office and reviewed at least every four years. The current version took effect on January 1, 2025, with its dollar figures set by the 2025 MCSF Supplement. Courts must follow it unless applying it would be unjust or inappropriate, and when they depart from it they have to explain why on the record.
The formula works in three stages, and this calculator follows the same order:
- Net income for each parent. Not take-home pay, but income as the manual defines it, less the specific deductions it allows.
- A base support obligation for each parent. The General Care Equation turns the family's combined net income into what it costs to raise the children, then splits that cost by each parent's share of the income.
- The parental time offset. The two obligations are balanced against the number of overnights the children spend in each home. The result is one payment, from one parent to the other.
After that, health insurance premiums, ordinary medical expenses, and child care are divided by the same income shares and added on. The calculator above estimates the base support figure, which is the largest part of most orders.
The General Care Equation, in plain numbers
The heart of the Michigan formula is a single equation from section 3.02(B) of the 2025 manual:
- C is the family's combined net monthly income.
- D, A and B come from the General Care Support Table for your number of children: find the highest income level (D) that does not exceed your family income, then take its base support amount (A) and marginal percentage (B).
- E is each parent's percentage share of the family income, rounded to the nearest hundredth of a percent.
Here is the 2025 table for two children. Notice that the marginal percentage falls as income rises: families spend a smaller share of each additional dollar on their children, and the formula mirrors that.
| Income level (D) | Base support (A) | Marginal % (B) |
|---|---|---|
| $2,013.94 | $767.31 | 37.92% |
| $3,272.65 | $1,244.59 | 24.31% |
| $4,531.37 | $1,550.63 | 20.43% |
| $7,198.27 | $2,095.42 | 20.20% |
| $9,432.22 | $2,546.70 | 17.87% |
| $17,871.57 | $4,055.06 | 16.16% |
A worked example, start to finish
Suppose you earn $4,500 a month in net income and the other parent earns $2,500. You share two children, who spend 73 overnights a year with you, about every other weekend plus some holiday and summer time.
- Family income. $4,500 + $2,500 = $7,000 a month. Both incomes are above the $1,255 low income threshold, so both count.
- Table row. The highest two-child income level that does not exceed $7,000 is $4,531.37, with base support of $1,550.63 and a marginal rate of 20.43%.
- Cost of the children. $1,550.63 + 20.43% × ($7,000 − $4,531.37) = $2,054.97 a month.
- Each parent's share. You earn 64.29% of the family income, so your base obligation is $1,321. The other parent's 35.71% share is $734.
- Parental time offset. With 73 overnights with you and 292 with the other parent, the offset equation nets the two obligations to a monthly payment from you of $1,259.
That is the figure this calculator's engine produces for the same inputs. A real order would then add each parent's share of health insurance, ordinary medical expenses, and any child care.
Why overnights move the number
Michigan's parental time offset, in section 3.03 of the manual, assumes that a parent who has the children overnight pays many of their day-to-day costs directly. It raises each parent's overnights to the power of 2.5 before weighing the two base obligations against each other:
Here Ao and Bo are each parent's annual overnights and As and Bs are their base obligations. The exponent is what gives the offset its shape. A handful of extra overnights barely changes the payment when one parent has the children most of the time, but the effect grows steeply as the schedule approaches an even split. Using the same two incomes as the example above:
| Your overnights per year | Monthly base support |
|---|---|
| 0 | $1,321 |
| 52 | $1,298 |
| 73 | $1,259 |
| 104 | $1,134 |
| 128 | $958 |
| 146 | $774 |
| 160 | $602 |
| 182 (about half) | $301 |
Two points follow from the equation. There is no overnight threshold to cross before the offset applies: the manual applies it whenever the approximate number of overnights can be determined. And an even schedule does not automatically mean no support. With equal time and equal incomes, the payment is $0, but with equal time and incomes of $6,000 and $4,000, the higher earner still pays about $265 a month.
The overnights used are the ones the children actually spend in each home, based on past practice or, without that, the current parenting time order. If the real schedule drifts at least 21 overnights from the one used to set support, either parent can ask the court to adjust it. Our child custody and parenting time page covers how those schedules are set.
"Net income" is not your take-home pay
The single biggest reason online estimates miss is the income figure. Section 2.01 of the manual says plainly that a parent's net income for support purposes will not be the same as take-home pay or taxable income. It starts broad, including wages, overtime, commissions and bonuses, self-employment and business earnings, rental income, unemployment and disability benefits, Social Security, military housing and ration allowances, and regular investment income, and then subtracts only the deductions the manual allows, such as:
- Actual federal, state, and local income taxes and FICA.
- Mandatory union dues and required retirement contributions.
- Spousal support paid to someone other than the other parent in this case.
- The parent's own cost of court-ordered or mandatory health coverage, and court-ordered life insurance for the children.
Voluntary 401(k) contributions, car payments, and most household bills are not deducted. And when a parent is voluntarily unemployed or underemployed, section 2.01(G) allows the court to impute a potential income based on that parent's work history, skills, and job opportunities, provided the parent has the actual ability and a reasonable likelihood of earning it. If you expect income to be disputed, that fight will affect the final number more than any other input.
Protections for low-income parents
The formula protects a parent's basic subsistence. The 2025 Low Income Threshold is $1,255 a month, taken from the 2024 federal poverty guideline. A parent whose net income is at or below that level owes 10 percent of it as base support, and that parent's income is left out of the family income used for the other parent's calculation.
Just above the threshold, a Low Income Transition Equation phases the full formula in gradually. It charges 10 percent of the threshold plus a percentage of the income above it, from 50 percent for one child to 70 percent for five or more, and applies whenever that figure is lower than the General Care Equation. For example, a parent with $1,500 in net income and one child, whose co-parent earns $4,000, would owe $320 under the General Care Equation but $248 under the transition equation, so the lower figure is that parent's base obligation. The calculator applies both rules automatically.
What the calculator leaves out
The base support estimate above is the core of a Michigan order, but a complete order includes more:
- Health care coverage. Premiums for covering the children are divided by income share. Coverage is presumed reasonable if it costs no more than 6 percent of the providing parent's gross income.
- Ordinary medical expenses. The 2025 Supplement presumes families spend $200 per child per year on co-pays, deductibles, and other uninsured costs. The payer reimburses a share in advance as part of the monthly order, and larger uninsured costs are split by income share.
- Child care. Work-related or education-related child care costs, after subsidies and tax credits, are divided by income share.
- Children from other relationships. A parent supporting other minor children has income reserved for them. After subtracting the portion of health premiums covering those children, the parent's income is multiplied by an adjustment factor: 83 percent for one additional child, down to 60 percent for five or more.
- Very high incomes. When a family's income greatly exceeds the top of the support tables, the court has discretion to fashion a different result under section 3.02(E).
When a court departs from the formula
Section 1.04 of the manual lets a court deviate when applying the formula would be unjust or inappropriate, but not simply because a parent disagrees with the formula's policies. Situations the manual lists include a child with special needs or extraordinary educational expenses, a parent who is a minor, extraordinary jointly accumulated debt, property awarded in place of support, extraordinary medical expenses, and irregular bonus income. Parents can also agree to a deviation, but the court must still find it appropriate and state on the record what the formula would have produced and why it is departing from it. A deviation argument needs evidence, which is where an attorney's preparation matters most.
When a Michigan support order can change
Support is not permanent. Either parent can ask for a review when circumstances change, and a Friend of the Court review must lead to a petition to modify when the recalculated amount differs from the current order by more than the minimum threshold: 10 percent of the current payment or $50 a month, whichever is greater. Common triggers include a job loss or raise, a change in the parenting time schedule, a new child, or a change in health coverage. Our post-judgment modification page explains that process in more detail.
Child support in Macomb County
In Macomb County, support cases run through the 16th Circuit Court and the Macomb County Friend of the Court on North Main Street in Mount Clemens, which investigates income, makes recommendations, and enforces orders. The Law Offices of Julie A. Hlywa is in downtown Mount Clemens and represents parents throughout the county, including Sterling Heights, Warren, Clinton Township, Shelby Township, Roseville, and St. Clair Shores.
Michigan child support: common questions
Does Michigan calculate child support on gross or net income?
Net income, but as the Michigan Child Support Formula defines it. Start from all income sources, then subtract only allowed deductions such as income taxes, FICA, mandatory union dues or retirement contributions, and certain insurance costs. The result is often different from your paycheck's take-home amount.
If we have 50/50 parenting time, does anyone pay child support?
Only if the incomes differ. With an even overnight split and equal incomes, the parental time offset produces zero. With an even split and unequal incomes, the higher earner still pays, though far less than with a standard every-other-weekend schedule.
Is there a minimum number of overnights before parenting time counts?
No. Under the 2025 formula, the parental time offset applies whenever the approximate number of overnights can be determined. At low overnight counts the reduction is small, and it grows quickly as the schedule approaches an even split.
What if the other parent is not working or is underemployed?
The court can impute a potential income to a parent who is voluntarily unemployed or underemployed, based on factors such as work history, education, skills, health, and available jobs. The court must find that the parent has the actual ability and a reasonable likelihood of earning that income.
Does having children from another relationship reduce child support?
It can. The formula reserves part of a parent's income for other minor children they are legally responsible for, using an adjustment multiplier that ranges from 83 percent of income for one additional child to 60 percent for five or more.
How long does child support last in Michigan?
Generally until the child turns 18. Under MCL 552.605b, a court can extend it while the child regularly attends high school full time with a reasonable expectation of graduating and lives full time with the recipient of support or at an institution, but never past age 19 and a half.
How accurate is this calculator?
The engine implements the 2025 General Care Equation, both low income equations, and the parental time offset, and its base support figures were checked against the official obligation tables published in the 2025 MCSF Supplement. What it cannot know is your net income as a court would find it, or the health care, child care, and deviation issues in your case. That is why the exact figure comes from a conversation with the attorney.
Sources: 2025 Michigan Child Support Formula Manual, sections 1.04, 2.01, 2.07 to 2.09, 3.01 to 3.06, and 4.05; 2025 Michigan Child Support Formula Supplement, sections 2.01 to 2.03 (State Court Administrative Office, Friend of the Court Bureau); MCL 552.605 and 552.605b; 45 CFR 302.56(e).
