Child Support Calculator
Estimate Australian child support payments using the Services Australia basic formula — based on both parents' incomes, care nights, and the number and ages of children.
This calculator follows the same 8-step basic formula Services Australia uses: each parent's income above the self-support amount, their share of care, the official Costs of the Children table, and who pays whom.
| Step | Parent A | Parent B |
|---|
What is a Child Support Calculator?
A child support calculator estimates how much one parent pays the other to share the costs of raising their children after separation. In Australia, child support is administered by Services Australia using a legislated formula — it isn't negotiated case-by-case or decided by gut feel. The formula combines both parents' incomes, how many nights each parent cares for the children, and the official Costs of the Children table to produce an annual rate.
Understanding the formula before you call Services Australia is genuinely valuable: it shows you what drives the number (income share versus care share), lets you model scenarios like changing care arrangements or income changes, and helps both parents have an informed conversation instead of guessing.
How is Child Support Calculated in Australia?
The basic formula (Formula 1) works through eight steps. Each parent's income above a self-support amount is combined; each parent's share of that combined income is compared with their share of care; and the difference is applied to the official cost of raising the children at that combined income level.
2. Combined Income = Parent A + Parent B child support incomes
3. Income % = each parent's share of the combined income
4. Care % = nights of care ÷ 365
5. Cost % = care % converted via the legislated table
(0–13% care → 0% | 14–34% → 24% | 35–47% → 25%+2/pt
48–52% → 50% | 53–65% → 51%+2/pt | 66–86% → 76% | 87%+ → 100%)
6. Child Support % = Income % − Cost %
7. Costs of the Children = from the official table (income, ages, number)
8. Annual Rate = positive Child Support % × Costs of the Children
Example: Parent A earns $95,000, Parent B earns $60,000, one child aged 8, with the child spending 52 nights a year with Parent A. Parent A's income share is about 68%, but their care share converts to a 24% cost share — so they pay roughly 44% of the child's assessed costs, which works out to around $5,800–$6,200 per year.
How to Use This Child Support Calculator
Enter each parent's adjusted taxable income — taxable income plus reportable fringe benefits, reportable super contributions, and net investment losses (this is broader than salary, and it's where many estimates go wrong). Select the number of children in the assessment and their age bracket — children 13 and over are assessed as costing more. Finally, enter the nights per year the children spend with Parent A; Parent B automatically has the remainder. The calculator runs the full formula and shows who pays, how much, and every step of the working.
What Your Results Mean
The headline figure is the annual child support one parent pays the other, also shown per month, fortnight, and week. The Costs of the Children figure is what the legislation says children at this combined income level cost to raise — the payment is each parent's unmet share of that cost. The breakdown table shows each parent's income percentage, care percentage, cost percentage, and resulting child support percentage so you can see exactly why the number is what it is.
Is This Calculator Accurate?
It implements the genuine basic formula with the 2025 self-support amount and 2025 Costs of the Children table, so for a standard single-case assessment it lands close to the official figure. It can't capture everything Services Australia assesses: multiple child support cases, relevant dependent children from new relationships, the minimum annual rate and fixed rate for low/non-lodging incomes, non-parent carers, or change-of-assessment decisions for special circumstances. The figures are indexed every January, so amounts drift slightly each year. Treat the result as a close planning estimate, then confirm with the official Services Australia estimator.
How to Choose Your Inputs
Income: Use adjusted taxable income from the most recent tax return — not take-home pay, and not just salary if there are fringe benefits, salary-sacrificed super, or investment losses. Care nights: Count actual overnight stays per year as they really happen, not what a parenting plan says if reality differs — Services Australia assesses actual care. Common patterns: every second weekend ≈ 52 nights, every second weekend plus half holidays ≈ 75–90 nights, shared week-about care = 182–183 nights. Ages: If any child turns 13 during the year, the assessment changes — model both brackets to see the difference.
Suitable for Women
Yes — the formula is gender-neutral and applies identically whichever parent has majority care. In practice, mothers are more often the majority-care parent and therefore more often the receiving parent. Two points worth knowing: child support received is not taxable income, and it can affect Family Tax Benefit Part A (the maintenance income test reduces FTB once child support exceeds a free area). If you receive FTB, the real financial picture is child support plus adjusted FTB — worth modelling together before agreeing to private arrangements.
Suitable for Men
Yes — and the same gender-neutral formula means fathers with majority care receive child support on exactly the same basis. For paying parents, the key facts: payments are not tax deductible, they're based on adjusted taxable income (so salary sacrificing doesn't reduce them — reportable super is added back), and increasing genuine care nights both reduces the formula payment and, more importantly, increases time with the kids. If income drops materially (job loss, reduced hours), lodge an income estimate with Services Australia promptly — assessments aren't backdated for late notifications.
Can I Use This to Plan a 50/50 Care Arrangement?
Yes — set Parent A's nights to 182 or 183 and the calculator models equal shared care. A common misconception is that 50/50 care means zero child support: it doesn't. With equal care, each parent's cost percentage is 50%, so child support still flows from the higher-income parent to the lower-income parent — the payment equals the income-share difference applied to the children's costs. Child support only nets to zero when both care and incomes are roughly equal.
Common Mistakes to Avoid
- Using take-home pay instead of adjusted taxable income. The formula uses gross ATI including fringe benefits and reportable super — using net pay understates both incomes.
- Assuming 50/50 care means no payments. Equal care with unequal incomes still produces a payment from the higher earner.
- Counting days instead of nights. The formula counts overnight stays; daytime care generally doesn't move the care percentage.
- Forgetting the age change at 13. Costs of the Children jump for teenagers — assessments rise when a child turns 13, which surprises many paying parents.
- Not reporting income changes promptly. Estimates only apply from when you lodge them — waiting months after a job loss means months of overpayment that's hard to recover.
Limitations of This Calculator
This tool models the basic Formula 1 for one child support case between two parents. It does not handle multiple cases (children with different other parents), relevant dependent children deductions, the minimum annual rate (~$1,700) or fixed rate for non-lodgers, agreements that replace the formula (binding or limited child support agreements), lump-sum or non-cash arrangements, or the over-18 extension for children finishing school. Care percentages are calculated from your nights input without the rounding conventions Services Australia applies at band edges. For formal figures and to start an assessment, use Services Australia's child support service.
Frequently Asked Questions
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