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Australian child support,
estimated.

Plug in both incomes, the number of children, and how the care nights are split. Get an instant estimate of what you'll pay or receive each month — based on the Services Australia formula.

Uses the official AU formula Runs entirely in your browser Takes 30 seconds
Your details
Step 1
Your annual income Gross / pre-tax
Co-parent's annual income Gross / pre-tax
Number of children Aged under 18
Your nights per fortnight 7 / 14
None 50% care Always
Your estimate
You pay
$0/mo
$0 per year
Share of your income 0%
Combined assessable income —
Cost of children —
Your income share —
Your care share —
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This is a simplified estimate. Your real assessment may differ. Verify with the official Services Australia estimator or a CSA-registered adviser before making decisions.
Atlas · The full picture

Child support is one piece. There are six more.

Atlas is a private planner for life after separation. See your child support sit inside your real monthly budget — alongside housing, kids costs, legal fees, super, and savings. Plus tools for the kids-week schedule and your post-separation goals.

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How it works

The Australian child support formula, in plain English.

Australian child support is calculated using a formula set by Services Australia. The headline idea is simple: both parents should contribute to the cost of raising a child in proportion to their income, adjusted for how much care each parent provides.

The estimator above runs the standard Formula 1 model — used in the most common case where both parents are the only assessable parents and the children are under 18. Here's what it actually does, step by step.

Step 01
Find each parent's child support income
Take each parent's adjusted taxable income and subtract the self-support amount (currently $29,446/yr). What's left is each parent's "child support income" — the income actually available to support the children. There's also an income cap of $184,051 per parent (2024–25 figure) — income above that threshold is excluded from the formula entirely. This cap applies per parent, not to the combined total.
Step 02
Combine the two and split it
Add both child support incomes together to get the combined income. Then work out each parent's percentage — this is the income share. If you earn 60% of the combined total, your income share is 60%.
Step 03
Apply the cost of children
The formula assigns a percentage cost based on the number of children: 17% for one, 24% for two, 27% for three, 30% for four or more. Multiply this by combined income to get the annual cost of the children.
Step 04
Subtract your care share
Calculate the percentage of nights you have the children (out of 14 in a fortnight) — this is your care share. Subtract care share from income share, then multiply by the cost of the children. The parent with a positive remainder pays. Negative means they receive.
Test a scenario

See how the numbers shift in common cases.

Tap any scenario to load it into the calculator above and see the result instantly.

What changes the figure

Six things that shift your child support amount.

Once you've run the calculator, it's worth knowing which lever moves the number.

  • Your income. The single biggest factor. Higher income = bigger income share = more paid (or less received).
  • The other parent's income. If their income rises, your income share falls — even if yours hasn't changed.
  • How many children are assessed. Each additional child adds roughly 5–7% to the cost-of-children rate, then it plateaus.
  • The split of care nights. Care is measured per fortnight. Moving from 5 nights to 7 changes the amount meaningfully.
  • The self-support amount. Indexed annually — both parents get to keep this much before child support is calculated.
  • Income types and deductions. Adjusted taxable income includes reportable fringe benefits, super contributions, net investment losses, and tax-free pensions — not just gross salary.

If your situation involves shared parental responsibility orders, more than one assessment, non-parent carers, change-of-assessment decisions, second families with relevant dependants, or income from a private business, treat the calculator result as a ballpark only.

Common questions

FAQ.

Is this calculator official?
No. This is an estimator built using the public Services Australia child support formula. It's accurate for most standard situations but not a substitute for an official assessment from Services Australia or advice from a CSA-registered adviser.
What income figure should I use?
Use your adjusted taxable income — your gross salary plus reportable fringe benefits, reportable super contributions, total net investment loss, tax-free pensions and benefits, and target foreign income. For most PAYG workers, gross salary alone is close enough. If you're self-employed or have investment income, the gap can matter.
How are care nights counted?
Care is measured per fortnight (out of 14 nights). 7 nights is equal shared care (50%). 5 nights is roughly 35% care. Day-time-only care counts differently — the official formula uses overnight stays as the proxy for care.
Why is my estimate different from my actual assessment?
Real assessments factor in things this estimator doesn't: more than four children, non-parent carers, change-of-assessment decisions, lump-sum maintenance, second families with relevant dependants, and other adjustments. Treat this as a ballpark and check Services Australia for the official figure.
Does it matter who pays whom?
Yes. The parent with the higher income share relative to their care share pays the other. If you earn more than half the combined income but have the kids less than half the time, you'll pay. If you earn less and have them more, you'll receive. The calculator shows the direction automatically.
Is the minimum amount really $1,638?
There's a minimum annual payment that applies in most cases where any liability exists, currently $1,638 per year per case. This applies even when the calculation produces a smaller figure, unless the paying parent has zero income or is otherwise exempt. The figure is indexed annually.
What is the self-support amount?
The amount of income each parent keeps for their own basic living costs before child support is calculated. Based on the Male Total Average Weekly Earnings figure, currently around $29,446 per year. Deducted from each parent's income before the formula runs. Indexed annually.
Is this calculator private?
Yes. Everything runs in your browser. Nothing is sent to a server, no signup is required, and your figures aren't saved unless you choose to use Atlas's full planner — which is also private and runs locally on your device.