Your parenting-time percentage, counted by overnights.

One line decides how child support is calculated in Ontario: 40 percent. Below 40 percent of the overnights, the parent with less time generally pays the full table amount of child support. At 40 percent or more for each parent, the arrangement becomes shared parenting under section 9 of the Federal Child Support Guidelines, and support is worked out as a set-off instead — each parent's amount is calculated, and the higher earner usually pays the difference. When one parent's time falls below 40 percent, the arrangement stops being shared parenting for support purposes and the other parent has primary care. The same schedule can lead to very different child-support outcomes depending on which side of the line it lands.

This free calculator works out each parent's share so you know where your schedule sits — no account, no fee. Parenting time is usually measured by overnights: the number of nights a year the child sleeps at each home. Enter a typical two-week schedule night by night, or annual totals, and it turns the nights into a percentage for each parent and shows which side of the 40 percent line the schedule lands on.

This is an estimate for planning. Courts assess the full-year pattern — holidays, school breaks, and vacation weeks all shift the count — and overnights are the usual way parenting time is counted, but not the only measure. A schedule sitting near 40 percent is exactly where the numbers get argued, so treat the result as a starting point rather than a final answer.