Child Support (Percentage) Calculator

ByJonathan Ross, Esq., JD ✓ Verified 📚 149 Calculators Authored

Legal Analyst & Statutory Modeling Consultant · Juris Doctor (JD), Member of the New York and District of Columbia Bars

📅 Published: Sep 28, 2026

The formula

standard: support = obligor income × rate (17/25/29/31/34% for 1–5+ children); shared placement (93+ overnights): each parent's obligation = income × rate × child's time with the other parent, then the two are offset

The percentage model in one paragraph

Percentage-of-income support ignores the receiving parent's earnings entirely (except under shared placement): the paying parent simply remits a fixed slice of their income — Wisconsin's rates are 17% for one child, 25% for two, 29% for three, 31% for four and 34% for five or more, applied to gross income. The philosophy is that support should mirror what an intact family would spend, and the marginal-cost data behind the rates shows spending per child falls as children are added — hence 25% for two rather than 34%. The model is fast, transparent and predictable; its criticism is that it disregards the custodial parent's resources, so two children in households with very different second incomes receive identical transfers. Federal rules accept any guideline methodology, which is why a handful of states still use it.

Shared placement flips the logic

When each parent hosts the child at least 25% of nights (93+ overnights a year), Wisconsin-style formulas stop being one-way. Each parent's percentage obligation is computed on their own income, then multiplied by the fraction of time the child spends with the other parent — the share of the duty that time with the other parent discharges. The two adjusted obligations are offset, and the larger pays the difference. The consequences are sharp: at 182 nights each (exactly equal time), the multipliers are both 0.499, so support collapses to roughly half the income differential's percentage — a $6,000/month payer versus a $3,000/month receiver transfers about $740 rather than $1,500. Crossing the 92-to-93 overnight line can therefore change the payment more than a $500/month raise.

Gross vs net, and what income counts

Percentage states differ on the base. Wisconsin uses gross income with narrow exclusions; some states start from net after taxes, mandatory deductions and prior support. "Income" typically sweeps in wages, self-employment profit, bonuses, commissions, overtime (averaged), unemployment and disability benefits, interest, dividends, rental profit and sometimes imputed income from underused earning capacity — a parent who quits a $90,000 job to earn $30,000 may still be assessed on $90,000. Capital gains, child support received for other children and means-tested benefits are commonly excluded. Before comparing models, make sure both are running on the same income definition; a 25%-of-gross order and a 25%-of-net order differ by 20–25%.

Frequently asked questions

What percentage of income is child support?

Under Wisconsin-style standard rates: 17% for one child, 25% for two, 29% for three, 31% for four, 34% for five or more, applied to gross monthly income. New York's CSSA uses nearly identical percentages (17/25/29/31/35) but applies them to combined parental income up to a cap (~$184,000 in recent years) and splits by income share.

Does the other parent's income matter in a percentage state?

Not in standard placement — that is the model's defining feature and its main criticism. It re-enters only under shared placement, where the receiving parent's obligation is computed and offset, and when courts deviate from guidelines for fairness.

What happens at exactly 92 vs 93 overnights?

A cliff. At 92 overnights the paying parent owes the full standard percentage; at 93 the obligation is multiplied by roughly 0.747 (the child's time with the other parent) and the offset begins — a drop of more than 25% in the support order overnight. This is why shared-placement thresholds are heavily negotiated.

Is child support tax-deductible?

No. The paying parent cannot deduct it, and the receiving parent does not report it as income — unlike alimony on pre-2019 divorce instruments, which changed with the Tax Cuts and Jobs Act for agreements after December 31, 2018.

Source & methodology

Wisconsin Statutes ch. DCF 150 (standard percentage rates 17/25/29/31/34% and the shared-placement offset formula, DCF 150.04); New York CSSA (Dom. Rel. Law § 240); federal guideline mandate at 45 C.F.R. § 302.56.

Child Support (Percentage): what this tool answers

Time is the one input nobody can renegotiate, which makes getting the arithmetic right worth the minute it takes. Searchers land on a Child Support (Percentage) page for three reasons — to plan, to compare options, and to check that somebody else’s arithmetic is honest. This tool serves all three, and everything after the calculator explains the model instead of hiding it.

Jurisdiction is the hidden coefficient. Two identical situations can price very differently across borders; the tool computes the mechanics, while the local rule-set is a question for counsel — and asking it early is what Child Support (Percentage) is actually for.

There is a habit that separates people who get useful answers from Family Law numbers: they decide what question the figure answers before they compute it. Child Support (Percentage) answers “Estimated monthly child support?” — and nothing else, which is precisely why the result is trustworthy.

What makes a calculation page trustworthy is that its copy is derived from its own arithmetic: here estimated monthly child support = $1,200.00 $/month, recomputed every time a field changes, and the sensitivity section ranks the inputs that move the result — Paying parent's monthly income first, at ≈10.0 % of the headline for a ten-percent error either way in that input. Work down the page and by the end you could re-derive the result in a spreadsheet from memory.

The Child Support (Percentage) formula, explained

Here is the complete model this tool runs — standard: support = obligor income × rate (17/25/29/31/34% for 1–5+ children); shared placement (93+ overnights): each parent's obligation = income × rate × child's time with the other parent, then the two are offset — with each input explained below. If a competitor’s page gives you a different answer from the same inputs, this is the text that settles which of you is right.

Paying parent's monthly income (example value $4,800.00) is a money amount; keep it in the currency the rest of your inputs use, or the comparison steps lose meaning. Use the figure exactly as the source document states it, not a rounded memory of it — an omitted line is the classic silent error.

Receiving parent's monthly income (needed only for shared placement) (example value $3,000.00) is a money amount; keep it in the currency the rest of your inputs use, or the comparison steps lose meaning. Use the figure exactly as the source document states it, not a rounded memory of it — an omitted line is the classic silent error.

Income basis (example value Gross income) is a branching choice rather than a figure you measure; the per-option effects are computed below. Keep every money input in the same currency; mixing systems quietly corrupts the comparison.

Deductions from gross to reach the basis (%) (example value 22) is a quantity rather than a category — precision here is cheap and worth having. Enter it exactly as your document states it — quoted annual, monthly and effective rates are three different numbers.

Number of children (example value 2 children) is a categorical input — the option you choose decides which numbers the formula uses. Count from the record, not the estimate; whole-number inputs are cheap to verify and expensive to get wrong.

Overnights per year with the paying parent (example value 40) is a numeric input whose unit is fixed by the label; a wrong unit is a wrong answer wearing a plausible disguise. Use the value as of today, not as of the last time you looked — time fields drift silently.

What each “Number of children” choice actually does: 1 child → $816.00 $/month · 2 children → $1,200.00 $/month · 3 children → $1,392.00 $/month · 4 children → $1,488.00 $/month · 5 or more children → $1,632.00 $/month These figures are computed from this engine, not estimated — switch the dropdown above and you will land on exactly these numbers.

A fully worked Child Support (Percentage) example

The tool prints its own working; this is the same arithmetic on the example values, reproduced so you can follow it by hand. Starting figures: Paying parent's monthly income, Receiving parent's monthly income (needed only for shared placement), Income basis, Deductions from gross to reach the basis (%). The computed estimated monthly child support comes out at $1,200.00 $/month, which the interpretation band labels “standard rate: 25% of income for 2 children”.

Standard obligation = income × rate for 2 children = $4,800 × 25% = $1,200.00/month.
Overnights (40) are below the 93-night shared-placement threshold, so no time adjustment applies: obligation stays at $1,200.00.
The receiving parent's obligation is not offset in standard placement: $0.00.
Net monthly transfer = $1,200.00 − $0.00 = $1,200.00; annually $14,400.00.

Applicable standard rate — 25.0 %. Read next to the headline, this is the figure that shows the shape of the trade-off.

Standard (sole-placement) amount — $1,200.00. If your inputs change, this is usually the first companion figure to move.

Paying parent's time-adjusted obligation — $1,200.00. Read next to the headline, this is the figure that shows the shape of the trade-off.

Receiving parent's offsetting obligation — $0.00. This is the number experienced users quote when the headline alone would mislead.

Net transfer — $1,200.00 $/month. Compare it against the main result of $1,200.00 $/month before drawing conclusions.

Overwrite any input above and every line of this example updates with it — the substitution is live, not a screenshot of somebody else’s numbers.

Scenario table: Child Support (Percentage) at ±10 % and ±20 % of the key input

Single-point answers invite false confidence, so the same engine was run across a band around the input that matters most here. Each row is a full recalculation of Child Support (Percentage), not an interpolation.

Paying parent's monthly income setting	Estimated monthly child support
80 % of the example value	$960.00 $/month
90 % of the example value	$1,080.00 $/month
example inputs	$1,200.00 $/month
110 % of the example value	$1,320.00 $/month
120 % of the example value	$1,440.00 $/month

The corridor runs from $960.00 $/month to $1,440.00 $/month across that band — which is the range worth planning inside rather than the single $1,200.00 $/month point estimate. Reproduce it in the form above by editing Paying parent's monthly income alone; the substitution steps will follow your figures exactly.

Sensitivity: which inputs change Child Support (Percentage) the most

This list was computed for this specific engine just now: each numeric input was nudged ±10 % while every other field held its example value, and the estimated monthly child support was recalculated from scratch. Read it as a map of where Child Support (Percentage) is fragile — drawn for the example inputs, which is the map you want when deciding what to measure carefully.

Nudge Paying parent's monthly income by ±10 % and Child Support (Percentage) lands between $1,080.00 $/month and $1,320.00 $/month (sensitivity ≈10.0 %)

Paying parent's monthly income is the dominant lever here: ten percent either way moves the result by about 10.0 %, from $1,080.00 $/month to $1,320.00 $/month. Spend your verification effort there first. The remaining fields can sit at safe defaults without materially changing the answer — knowing which is which is what separates a careful calculation from an anxious one.

What a Child Support (Percentage) of $1,200.00 $/month means in practice

Nobody acts on a bare figure — they act on a figure with a comparison attached. The verdict attached to the default calculation — “standard rate: 25% of income for 2 children” — is one band on a ladder your own figure may sit somewhere else on. The sensitivity list shows how far a modest input error moves you along that ladder: for Paying parent's monthly income, ±10 % covers $1,080.00 $/month to $1,320.00 $/month. The practical reading rules: read the band as a starting hypothesis, then test it: change the two dominant inputs by ten percent and see whether the verdict survives. Verdicts that survive stress are the ones worth acting on.

Where Child Support (Percentage) sits next to similar measures: this tool answers “how much is the Child Support (Percentage)”, while the related calculators answer “what do I do about it”. Reading the result alone tends to over-weight a single snapshot; pairing it with the companion tools above turns the number into a decision.

The errors that quietly break a Child Support (Percentage) figure

Reporting the headline and quietly discarding Applicable standard rate. The companions are where the shape of the trade-off survives the rounding.

This model has its own particular trap: Paying parent's monthly income carries ≈10.0 % of the response per ten percent of error, so effort spent elsewhere is largely decorative.

The subtlest error is answering the wrong question precisely. Confirm that estimated monthly child support is actually the quantity your decision needs — the arithmetic is flawless either way, which is what makes the mistake invisible.

A quick check for any Child Support (Percentage) figure

Recompute once with the dominant input deliberately set low, and see whether the decision changes.
Check that every field the formula needs actually arrived from a document, not from recollection.
Re-verify Paying parent's monthly income against a source document — ten percent of error there moves the headline by ≈10.0 %.
Note the date and the inputs beside the number so the figure can be audited later.
Verify each input against its original source document, not memory.
Run the ±10 % stress on the top two levers and check that your conclusion survives both.

Step by step: getting a trustworthy Child Support (Percentage) out of this tool

The tool does the arithmetic; the routine below is what makes the arithmetic trustworthy. Five steps, a minute total — and afterwards you will know not just what the number is, but which assumption produced it.

Step 1 — one document, one pass. Open the statement, label or record that holds paying parent's monthly income, receiving parent's monthly income (needed only for shared placement), income basis, deductions from gross to reach the basis (%), number of children, overnights per year with the paying parent and transcribe straight into the form. Transcription from a single source removes the mismatch errors that appear when figures are assembled from three different places. Say the answer out loud before you save it; if it sounds wrong, the model did not change, your understanding did.

Step 2 — enter the conservative case first. Resist the flattering scenario. Type the inputs you would defend in front of a sceptical reader, read the Estimated monthly child support ($1,200.00 $/month for the example values), and note the verdict band. The fastest sanity test is to guess the answer first and see how far the calculation disagrees.

Step 3 — measure what deserves measuring. The ranked levers above tell you where a careful figure pays off. Everything else can stay approximate, which is a licence to stop hunting for data you do not need. The inputs are the part of the work that nobody else can do for you.

Step 4 — run the scenario trio. Expected, pessimistic, optimistic. The gap between pessimistic and expected is the number to plan against; the optimistic result is useful only as a ceiling. Numbers are cheap to produce and expensive to retract; the extra minute is the cheapest insurance available.

Step 5 — record the context, not just the number. Note today’s date and the inputs alongside the $1,200.00 $/month output. Six months from now the context is what turns this figure into a trend. Rounding early is the quietest way to introduce a permanent error.

Where Child Support (Percentage) matters in practice

Numbers earn their keep in conversations, and Child Support (Percentage) is no exception. In Legal & Law discussions around Family Law, this figure decides whether an option stays on the table: it converts an opinionated debate into an arithmetic one, and arithmetic is the only referee both sides accept. Note the assumption you are least sure about; that is where the real risk lives.

Used properly this is a five-minute filter that saves weeks. Compute Child Support (Percentage), reject what fails, and only then bring in the expensive analysis for the survivors. Say the answer out loud before you save it; if it sounds wrong, the model did not change, your understanding did.

Nothing here is stored or transmitted, so the habit of checking is free: open the page, re-enter current figures, compare with the number you saved last time. The input you reach for first is usually the one you measured longest ago.

Child Support (Percentage) — frequently asked questions

What affects Child Support (Percentage) the most?

Child Support (Percentage) is driven above all by Paying parent's monthly income. Perturbing only that field by ten percent either way produced $1,320.00 $/month against the $1,200.00 $/month baseline — a ≈10.0 % response.

How much does the “Number of children” choice change the answer?

A great deal, on these inputs: Child Support (Percentage) comes out at $816.00 $/month on the lowest option (“1 child”) and $1,632.00 $/month on the highest (“5 or more children”). Each option is listed with its computed value so you can see what the choice is worth before you make it.

What is a typical Child Support (Percentage)?

There is no honest universal average for Child Support (Percentage), but there is a reference point: the defaults on this page produce $1,200.00 $/month (standard rate: 25% of income for 2 children). Replace the inputs with your own and compare — that comparison is the useful meaning of “typical”.

How do I calculate Child Support (Percentage) by hand?

Three steps: write the formula (standard: support = obligor income × rate (17/25/29/31/34% for 1–5+ children); shared placement (93+ overnights): each parent's obligation = income × rate × child's time with the other parent, then the two are offset), insert your values, and simplify. The worked example section shows exactly that chain for the default inputs; replicating it once on paper teaches you more about Child Support (Percentage) than any number of calculator runs.

What happens to Child Support (Percentage) if paying parent's monthly income changes by 10 %?

The engine was re-run with that field moved by ten percent while everything else stayed fixed: the estimated monthly child support goes across $1,080.00 $/month to $1,320.00 $/month, a swing of roughly 10.0 % around the $1,200.00 $/month baseline. That ratio is the practical definition of how much this input matters.

Is the Child Support (Percentage) result of $1,200.00 $/month good or bad?

The tool answers “what”, not “whether”: $1,200.00 $/month carries the verdict “standard rate: 25% of income for 2 children” for the default case, which is a starting interpretation rather than a verdict on your situation. Re-run with your own figures and compare the bands.

Is this Child Support (Percentage) legally binding?

No. It is an estimate that models the stated formula. Binding figures depend on jurisdiction, contract wording and procedure — which is why the disclaimer sits between this page and any professional action.

Can Child Support (Percentage) be negative or empty?

Yes, and that is informative rather than broken: a negative Child Support (Percentage) usually means the inputs encode an outflow or a shortfall, and the verdict band above labels exactly that situation instead of hiding it.

What percentage of income is child support?

Does the other parent's income matter in a percentage state?

Does this Child Support (Percentage) tool store my numbers?

No. The entire calculation runs in your browser session; nothing entered above is transmitted or saved, which is the correct behaviour for sensitive Legal & Law figures and the reason you can re-run this page as often as you like.

Key terms on this page

Applicable standard rate: 25.0 % for the Child Support (Percentage) worked case; it sits next to the main result because it carries context the headline leaves out.
Standard (sole-placement) amount: $1,200.00 for the Child Support (Percentage) worked case; it sits next to the main result because it carries context the headline leaves out.
Paying parent's time-adjusted obligation: $1,200.00 for the Child Support (Percentage) worked case; it sits next to the main result because it carries context the headline leaves out.
Estimated monthly child support: The primary output of this tool: $1,200.00 $/month for the default inputs, computed exactly from standard: support = obligor income × rate (17/25/29/31/34% for 1–5+ children); shared placement (93+ overnights): each parent's obligation = income × rate × child's time with the other parent, then the two are offset.
Worked example: Every substitution in order, from the example inputs to $1,200.00 $/month — the audit trail for the headline figure.
Verdict band: The plain-language label — here “standard rate: 25% of income for 2 children” — mapping the computed figure onto experience-based ranges for Legal & Law.
Sensitivity (±10 %): How far the Child Support (Percentage) moves when a single input is nudged ten percent either way; the ranked list on this page is computed live from this engine.

Methodology, sources and limits

There is no black box on this page — the engine evaluates standard: support = obligor income × rate (17/25/29/31/34% for 1–5+ children); shared placement (93+ overnights): each parent's obligation = income × rate × child's time with the other parent, then the two are offset. Source of record: Wisconsin Statutes ch. DCF 150 (standard percentage rates 17/25/29/31/34% and the shared-placement offset formula, DCF 150.04); New York CSSA (Dom. Rel. Law § 240); federal guideline mandate at 45 C.F.R. § 302.56. Where a professional version of this calculation differs, it differs in inputs and jurisdiction-specific coefficients, not in the algebra — which is why re-checking your inputs beats hunting for a second calculator.

Treat the output as a precise answer to the question you typed: exact arithmetic, transparent formula, published source, no hidden rounding. The promise to the reader is narrow and testable: same inputs, same output, no silent rounding, and no figure presented without the formula that produced it.

Next steps after the calculation

Re-run whenever a start date moves — time calculations compound small shifts into large misses.

The audience here is people planning around a point or span in time. Everything you need to defend the result — formula, substitution, sensitivity, source — is printed above, so the only remaining variable is the honesty of your inputs.