Get a fast, private estimate based on the official Services Australia formula — before you negotiate, mediate, or speak to a lawyer.
Built by a former Department of Human Services child support officer. Calculations follow the legislated 8-step formula and are accuracy-tested against Services Australia's own estimator. See our methodology →
Free to use. Results in under 1 minute.
Based on the current Services Australia formula, including all 6 formulas.
Handles shared care, low-income cases, and scenarios the government estimator gets wrong.
No login. No account. Your numbers stay private.
A child support calculator estimates the amount a paying parent owes under the formula set out in the Child Support (Assessment) Act 1989. It compares each parent's taxable income after a self-support deduction, then applies a care cost conversion to determine each parent's share of the costs of raising the child.
How many nights of care you provide directly affects how much child support is paid. Services Australia uses these statutory thresholds:
| Care level | Care % | Nights/year | Cost % | Payer role |
|---|---|---|---|---|
| Below regular care | 0–13% | 0–51 | 0% | Payer only |
| Regular care | 14–34% | 52–127 | 24% | Payer onlynil liability possible |
| Shared care | 35–47% | 128–175 | 25% +2% per pt >35% | Income determines the payer |
| 48–52% | 176–189 | 50% | ||
| 53–65% | 190–237 | 51% +2% per pt >53% | ||
| Primary care | 66–86% | 238–313 | 76% | nil liability possiblePayee only |
| Above primary care | 87–100% | 314–365 | 100% | Payee only |
This calculator gives you an estimate based on the same formula Services Australia uses. It is useful for understanding where the numbers are likely to land — before you negotiate a private agreement, prepare for mediation, or book a lawyer.
This is not a formal child support assessment. Only Services Australia can issue that. Your actual assessment may differ if either parent has income that is hard to verify, an Application for a Change of Assessment has been granted, or there is a binding child support agreement in place.
The estimate gives you a baseline for negotiating a private agreement with the other parent, or understanding what a formal Services Australia assessment is likely to produce. You can also use the result to prepare for mediation.
Some matters go beyond what a standard estimate can cover — hidden income, disputed care arrangements, self-employment, or an existing binding agreement. If that's your situation, speaking to a family lawyer before acting on any number is worth considering.
Run a new estimate with updated figures. If the gap between your current assessment and the new estimate is significant, a Change of Assessment may be the right next step.
Child support in Australia is calculated using an 8-step formula under the Child Support (Assessment) Act 1989. The amount depends on both parents' adjusted taxable incomes, the percentage of time each parent cares for the children, and how many children are involved. There's no single figure that applies to everyone — the calculation varies significantly based on those inputs.
The fastest way to get your estimate is to use the calculator above. It takes the same inputs Services Australia uses and gives you a result in under two minutes. → Calculate your estimate
Child support uses an 8-step formula. In plain terms, it works like this:
The result is the annual child support amount. Our calculator applies this logic automatically — you enter your figures, it does the maths. For a detailed breakdown of each formula type, see our child support formula guide.
Child support uses your adjusted taxable income (ATI), not your take-home pay or gross salary alone. ATI includes:
It does not include Family Tax Benefit or most Centrelink payments. In 2026, a self-support deduction of $31,046 is removed from each parent's ATI before the formula is applied — only income above this threshold counts. Use your most recent Notice of Assessment from the ATO as your starting figure.
Care percentage has four key thresholds in the formula:
| Care % | Nights/year | Nights/fortnight | Care level | Cost % |
|---|---|---|---|---|
| 0–13% | 0–51 | 1 | Less than regular care | 0% |
| 14–34% | 52–127 | 2–4 | Regular care | 24% |
| 35–47% | 128–175 | 5–6 | Shared care | 25% + 2% per point over 35% |
| 48–52% | 176–189 | 7 | Shared care | 50% |
| 53–65% | 190–237 | 8–9 | Shared care | 51% + 2% per point over 53% |
| 66–86% | 238–313 | 10–12 | Primary care | 76% |
| 87–100% | 314–365 | 13–14 | More than primary care | 100% |
Enter your exact care arrangement into the calculator to see how your cost percentage affects the payment.
Equal care does not automatically mean zero child support.
At 50/50 care, both parents are treated as sharing the costs of the children equally — but child support is still calculated based on the income difference between the two parents. The parent with the higher income typically pays the parent with the lower income, even when care is split equally.
The exact amount depends on how large the income gap is. → Calculate your 50/50 shared care estimate
There is a minimum annual child support amount that applies even if the paying parent has little or no income. In 2026, that figure is $551 — indexed each year in line with the Consumer Price Index. If the paying parent earns nothing at all, the minimum rate still applies. It is not reduced to zero. The minimum assessment reflects the expectation that all parents contribute something toward the cost of raising their children. You can use the calculator to see how payments scale from the minimum as income increases.
The amount for a single child varies widely based on both parents' incomes and the care arrangement. As a reference: a paying parent earning $80,000 with the other parent earning $50,000 and 50/50 care would typically pay in the range of $5,000–$7,000 annually — but this is illustrative only.
The only way to get a figure that reflects your actual income and care percentage is to run the calculator. → Calculate child support for one child
Yes, in some circumstances. Child support assessments are not permanent. If your income has dropped significantly since your last assessment, you may be able to apply for a Change of Assessment — a formal process through Services Australia to have your payments recalculated.
Changes are assessed against eight specific grounds set out in the legislation, including major income changes, shifts in care arrangements, school fees or medical expenses, and supporting a new family. If both parents agree on a different amount, they can also enter a binding child support agreement.