Child Support Modification Calculator
Calculate revised child support based on changed income circumstances.
About this calculator
This calculator illustrates one specific, real child support guideline: Wisconsin's Percentage of Income Standard, in place since 1987 and codified today at Wis. Admin. Code § DCF 150, which sets support as a flat percentage of the paying parent's own gross income -- 17% for one child, 25% for two, 29% for three, 31% for four, and 34% for five or more -- with no adjustment for the receiving parent's income. New Payer Income is the only input that moves New Monthly Support, since the obligation is simply New Payer Income multiplied by the percentage for Number of Children, divided by 12.
This is deliberately a single, real state's approach shown as one example, not a universal formula: most US states instead use an 'income shares' model that combines both parents' incomes to set a total child-rearing cost, then splits it proportionally -- a state using that model would produce a materially different number here. Change Amount and Change Percentage compare the recalculated New Monthly Support against your entered Current Monthly Support, and Meets Modification Threshold flags whether that change clears a commonly cited 15% materiality bar -- many states require a substantial change in circumstances before a court will hear a modification petition, but the exact percentage (or whether a state uses a percentage at all, versus a flat dollar threshold) varies by jurisdiction. This tool does not model imputed income, additional children from other relationships, shared-custody adjustments, healthcare or childcare cost add-ons, or any state's actual current statutory table -- treat every figure here as an illustrative estimate for one hypothetical guideline, not legal advice or a substitute for your state's official worksheet.
Legal Disclaimer
This calculator provides general estimates only and does not constitute legal advice. Laws, regulations, and court procedures vary significantly by jurisdiction. Consult a licensed attorney in your area for advice specific to your situation.
Inputs
Results
New Monthly Support
$1,250.00
Change Amount
$50.00
Figures current as of 1987. Source: Wis. Admin. Code § DCF 150, Child Support Standard — percentage-of-payer-gross-income guideline: 17% (one child), 25% (two), 29% (three), 31% (four), 34% (five or more).
How to Use This Calculator
- Enter Current Monthly Support and Original Payer Income (the paying parent's income when support was set).
- Input New Payer Income reflecting the paying parent's current circumstances.
- Set Number of Children covered by the order.
- Review New Monthly Support and Change Amount using a flat percentage-of-income guideline (Wisconsin's standard, illustratively).
- Check Meets Modification Threshold against a commonly cited 15% change benchmark — actual thresholds vary by state.
- Consult a family law attorney — courts require a formal motion to modify existing orders, and most states use a different guideline model than the one shown here.
How the result changes with New Payer Income
| New Payer Income | New Monthly Support | Change Amount |
|---|---|---|
| $30,000.00 | $625.00 | -$575.00 |
| $45,000.00 | $937.50 | -$262.50 |
| $90,000.00 | $1,875.00 | $675.00 |
| $150,000.00 | $3,125.00 | $1,925.00 |
What each input means
- Current Monthly Support
- Current monthly child support payment.
- Original Payer Income
- Paying parent's gross annual income when support was set.
- New Payer Income
- Paying parent's current gross annual income.
- Number of Children
- Number of children covered by the order (5 or more uses the same rate as 5).
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersCurrent Monthly Support = 1200, Original Payer Income = 80000, New Payer Income = 60000, Number of Children = 2 = 4 input(s) provided
- Calculate New Monthly SupportNew Monthly Support1250 = $1,250
- Calculate Change AmountChange Amount50 = $50
- Calculate Change PercentageChange Percentage4.2 = 4.2
- Calculate Meets Modification ThresholdMeets Modification ThresholdNo — below a common 15% threshold = No — below a common 15% threshold
Figures and sources
- Wisconsin Percentage of Income Standard (DCF 150) (1987) — Wis. Admin. Code § DCF 150, Child Support Standard — percentage-of-payer-gross-income guideline: 17% (one child), 25% (two), 29% (three), 31% (four), 34% (five or more).
Engine last updated . Checked against 3 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why doesn't this calculator ask for the recipient parent's income?
It models Wisconsin's real Percentage of Income Standard, which by design sets support as a flat percentage of only the paying parent's gross income -- the receiving parent's income doesn't enter the formula at all under that specific guideline. States using an 'income shares' model instead (most US states) DO factor in both parents' incomes, which is why this tool's result won't match every state's actual worksheet.
What single input drives New Monthly Support?
New Payer Income is the only input that changes New Monthly Support, since the obligation is calculated as New Payer Income multiplied by a fixed percentage for Number of Children, divided by 12. Number of Children shifts which percentage bracket applies but doesn't otherwise change the formula's structure.
Is a 15% change always required to modify child support?
No. 15% is a commonly cited materiality threshold used as one illustrative benchmark, but actual rules vary significantly by state -- some use a different percentage, some use a flat dollar-amount threshold instead of a percentage, and some leave it to judicial discretion. Check your state's specific modification statute or consult a family law attorney for the actual standard that applies to your case.
Does this reflect my state's actual child support formula?
Only if your state uses Wisconsin's specific Percentage of Income Standard, which is not the majority approach. Most states use an income-shares model that also factors in the receiving parent's income and often applies a non-linear schedule rather than a flat percentage, so this calculator's result should be treated as one illustrative example, not a stand-in for your state's official guideline worksheet.
What happens if Number of Children is set above 5?
The input caps at 5, matching Wisconsin's real published table, which groups '5 or more children' into a single 34% bracket rather than defining separate, higher rates for six or more children. Entering more than 5 children isn't possible with this calculator's current input range.
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