How to split child expenses after divorce: a free co-parenting expense calculator
SplitDay Team · Updated · Runs entirely in your browser
This free calculator works out how two separated parents share the children’s costs. Type both names, choose 50/50, a split in proportion to each parent’s net income or your own percentages, and enter the monthly amounts — childcare, school fees, activities, medical costs, clothing, camps and the rest. You get each parent’s share per category, monthly and yearly totals and a plain-language summary to copy or print. No account, no email, no upload: the maths runs in your browser and nothing you type leaves it.
Nothing you type leaves this page. The calculator keeps your numbers in memory and forgets them when you close the tab, unless you tick “remember these numbers in this browser”, which stores them only on this device. Copy or print the summary before you leave — or keep the running ledger in the SplitDay app, where every expense and receipt stays.
Keep the split running every month in SplitDay
This page splits one list, once. In the SplitDay app every expense is logged as it happens — a photo of the receipt, who paid and the split ratio — and a running balance shows who owes whom. Share the household with your co-parent and you both see the same list and the same balance. Free to start: the free plan includes 3 expenses and 3 receipt scans a month; Pro raises the quota to unlimited expenses and 50 receipt scans a month.
What the kids’ expense split calculator does
Separated parents rarely fall out over the big-ticket items. It is the long tail of small, recurring costs — the after-school club, the dentist, the winter coat — that goes unrecorded and unshared. This calculator puts the whole list on one page and splits every line by a rule both of you can see. Choose equal halves, a split in proportion to each parent’s net income, or your own percentages; the table shows what each parent carries per category, per month and per year, and a plain-language sentence states the result in a form you can paste into a message.
It is built for the shared expenses that sit alongside a child support arrangement — the costs parents agree to divide between themselves — and it does not calculate child support, which follows the law of the place where the children live. Nothing is uploaded: the maths runs in your browser, and the only thing that leaves the page is the summary you choose to copy or print.
How it works
- Type both parents’ names and choose how to split: 50/50, in proportion to monthly net income (two income fields appear), or custom percentages that add up to 100.
- Go through the expense list. Rename, remove or add categories and enter the monthly amount for each — for seasonal costs such as camps, the yearly figure divided by 12.
- Optionally set an extraordinary-expense threshold. Any single item above it is listed in its own table so the two of you can agree it separately.
- Read the per-category table, the monthly and yearly totals for each parent and the one-paragraph summary. Copy it into a message or print it — and tick “remember these numbers in this browser” if you want them waiting next time.
50/50, in proportion to income, or custom percentages: what each method means
| Method | How each parent’s share is worked out | Example on a $650 childcare bill |
|---|---|---|
| 50/50 | Every line is halved. Earnings do not matter. | $325.00 each |
| In proportion to net income | Each parent’s share equals their part of the combined monthly take-home pay. | Incomes of $4,200 and $3,000 give 58.3% and 41.7%: $379.17 and $270.83 |
| Custom percentages | Any split the two of you agree, applied to every line. The two percentages must add up to 100. | 70/30 gives $455.00 and $195.00 |
The same rule applies to every line. A cost that one parent carries alone belongs off the list rather than in it, and a cost the two of you split differently from the rest is easiest handled as its own calculation. The page does not recommend a method: that is for the two of you — or your agreement or mediator — to settle, and switching between the three is the quickest way to see what each one means in money.
What counts as an extraordinary expense
Most parenting agreements separate the predictable monthly costs from the large or irregular ones — orthodontics, glasses, a laptop for school, a residential camp, therapy, a school trip — and handle the second group item by item: agree before the money is spent, keep the receipt, reimburse the other parent’s share. The threshold on this page is simply the line between the two groups. Set it to whatever the two of you treat as “big”; anything above it moves to its own table with its own subtotal, split by the same rule, so it can be discussed on its own rather than buried in the monthly list.
Frequently asked questions
Is the kids’ expense split calculator free, and does anything leave my browser?
It is free, and nothing leaves your browser. There is no account, no email field and no upload: the calculator is JavaScript running on your own device, the numbers stay in memory, and nothing is sent to us or to anyone else. If you tick “remember these numbers in this browser”, they are stored only on this device, and unticking the box deletes them.
Is this a child support calculator?
No. Child support follows the law of the place where the children live and is set by agreement or by legal process; this page does not compute it. The calculator covers the shared expenses two parents agree to divide between themselves — childcare, activities, medical costs and so on — which may sit alongside, or inside, whatever child support arrangement applies. Treat the result as a starting point for a conversation, not as a legal figure.
Which is better, 50/50 or in proportion to income?
That is for the two of you — or your agreement or mediator — to decide, and this page deliberately does not recommend one. 50/50 means each parent pays half of every item regardless of earnings. In proportion to income means each parent’s share equals their part of the combined net income, so a parent earning 4,200 against 3,000 carries 58.3%. Custom percentages cover any other arrangement. Switch between the three and compare the monthly totals before you talk.
What counts as an extraordinary expense?
Usually a cost that is large, irregular or not foreseeable in a monthly budget: orthodontics, glasses, a laptop for school, a camp, therapy, a school trip. Many parenting agreements handle these separately from routine costs — agree before spending, keep the receipt, reimburse the other parent’s share. The threshold here is yours to set; anything above it is listed in its own table so it can be agreed item by item.
How does the rounding work?
Every line is split to the cent. When a share does not land on a whole cent, the odd cent goes to the line closest to rounding up, so that each parent’s column adds up exactly to their share of the total and the two columns add up exactly to the list. Yearly figures are twelve times the monthly ones.
Is this the same as the expense tracker in the SplitDay app?
No. This page splits one list once and forgets it. In the app every expense is logged as it happens with a photo of the receipt, who paid and its split ratio; a running balance shows who owes whom, and both parents see the same list when the household is shared. The free plan includes 3 expenses and 3 receipt scans a month; Pro raises the quota to unlimited expenses and 50 scans a month.
This calculator splits shared expenses by agreement between the parents. It is not child support — that follows the law of the place where the children live, is set by agreement or by legal process, and is not computed here. This is general information, not legal advice; for your own situation consult a family-law attorney licensed where your case is heard. See also shared custody law by country.
Turn a one-time split into a balance that keeps itself
Log each expense in SplitDay as it happens — receipt photo, who paid and the split — and the balance between you updates itself. Free to start, and it works even if only one parent uses it.