Parenting Time 40% Calculator Ontario

Quick Answer

What is the 40% rule for child support in Ontario? Under section 9 of the Federal Child Support Guidelines (and the matching section 9 of Ontario’s Child Support Guidelines), child support is calculated differently when each parent has at least 40% of parenting time over the course of a year. 40% of a 365-day year is 146 overnights (147 in a leap year). Below that, the table amount normally applies. Reaching 40% does not automatically cancel support: the court then considers both parents’ table amounts, the increased costs of shared parenting and each household’s circumstances.

Ontario Parenting Time 40% Calculator

Free, private and anonymous: the calculation runs in your browser. Nothing you enter is sent to Tailor Law or stored, and no cookies are used.

How do you want to enter the schedule

Regular pattern (Parent B time)Percentages are based on overnights in a repeating two-week cycle.

Holiday and summer adjustment for Parent B (overnights per year, optional)Use a positive number for extra holiday or summer overnights with Parent B, or a negative number for fewer.

Year length Leap year (366 days)

Enter your figures and select Calculate.

How the calculator works

Parent B share = (Parent B overnights in the cycle ÷ nights in the cycle) × days in the year, plus any holiday adjustment, ÷ days in the year.
Threshold met when both parents are at 40% or more: Parent B time × 5 ≥ 2 × days in the year, and the same for Parent A.

Patterns repeat over 14 nights, so a 2-2-3, 2-2-5-5, 5-2-2-5 or week-on/week-off rotation gives each parent exactly 7 of 14 nights (50%).
Overnights per week are converted to a year by multiplying by days in the year ÷ 7. Hours per week are divided by 168.
40% of 365 days is exactly 146. In a leap year 40% is 146.4, so 147 whole overnights are needed. The calculator treats exactly 40.0% as meeting the threshold because section 9 says “not less than 40%”.
It also flags when one parent has more than 60% of the year, which the Guidelines define as the “majority of parenting time”.

Worked example

A proposed schedule gives Parent B every other weekend (Friday and Saturday nights) plus one midweek overnight every week. That is 4 of every 14 nights: 4 ÷ 14 × 365 = 104.3 overnights a year, or 28.6%. The 40% threshold is 146 overnights, so Parent B is about 42 overnights short.

If the weekends ran from Thursday to Monday morning (4 nights) and the weekly midweek overnight stayed, Parent B would have 6 of 14 nights: 156.4 overnights, or 42.9%. Both parents would then be at or above 40%, and section 9 would govern the child support calculation.

Why 40% matters for child support

In most cases, the parent with less parenting time pays the child support table amount set by the Guidelines. When each parent exercises at least 40% of parenting time over a year, section 9 requires the court to take three things into account instead: the table amounts for each parent (often compared as a set-off), the increased costs of shared parenting, and the conditions, means, needs and other circumstances of each parent and child. The result can be close to the simple set-off, or quite different from it.

Because so much can turn on a few overnights, the 40% threshold is often argued in parenting disputes. A calculator helps you see where a proposed schedule lands before you agree to it.

Limitations

Courts do not use a single counting method. They may count overnights, days, hours, or time the parent is responsible for the child, and can look at the real schedule over a year rather than the written one.
Time the child is at school or daycare, and holidays and summer, can be allocated differently from case to case.
Section 9 sets a threshold, not an amount. This tool does not calculate the child support that results.
Parenting arrangements must always follow the child’s best interests, not a support calculation.

Frequently Asked Questions

How many overnights is 40% in Ontario?

40% of a 365-day year is 146 overnights. In a leap year (366 days) it is 146.4, so 147 whole overnights are needed. Some courts count hours or days instead of overnights, which can change the result.

Does 50/50 parenting mean no child support in Ontario?

Not necessarily. When each parent has at least 40% of parenting time, section 9 of the Child Support Guidelines requires the court to consider both parents’ table amounts, the extra costs of shared parenting and each household’s circumstances. The higher-income parent often still pays some support.

Do holidays and summer count toward the 40%?

Yes. Section 9 looks at parenting time over the course of a year, so holidays, summer vacation and special occasions are part of the count. Use the holiday and summer adjustment in the calculator to add or subtract those overnights.

Is the 40% threshold counted in overnights or hours?

The Guidelines do not prescribe a method. Ontario courts have counted overnights, days and hours, and they look at the real pattern of care. Overnights are a common starting point, which is why the calculator uses them by default and offers an hours option.

What happens if I am just under 40%?

If one parent is below 40%, section 9 does not apply and the table amount is normally payable by the parent with less time. Because the difference can be significant, the counting method and actual time exercised are often disputed. Get legal advice on your specific schedule.

Sources

Related calculators

Legal review: Reviewed by Deepa Tailor, Founder & Managing Director · September 2026. Calculator version: 2026-09-26. Prepared by Tailor Law Professional Corporation from the official sources listed above.

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This calculator provides general information about Ontario family law and an estimate based only on the figures you enter. It is not legal advice and does not create a lawyer-client relationship. Results can differ from what a court orders or what parties agree. Speak with a lawyer before relying on any figure.

Parenting Time 40% Calculator for Ontario