Baby and Parenting Calculators
Car seat stage.
Enter your child’s age, weight and height and your province to see which stage they are at, what the law requires where you live and what safety groups recommend. Runs in your browser; nothing is sent or stored.
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Fill the form and press Calculate.
Not medical advice. This is general safety information, not legal advice or a substitute for your seat’s manual. Provincial laws change and are summarized for information only; check your provincial transportation ministry. Have a certified child passenger safety technician check your installation.
Worked example
A 2-year-old in Ontario weighing 13 kg and 88 cm tall: Ontario requires a child seat suited to their size between 9 and 18 kg, and best practice says to keep rear-facing until the seat’s rear-facing limit and only then move to a forward-facing harness. A 5-year-old at 20 kg and 110 cm is at the harness-or-booster stage and Ontario requires a booster until 145 cm, 36 kg or 8 years, whichever comes first.
How it works
Legal minimums (Canada). Provinces and territories set their own rules. Most require rear-facing at least until 9 kg (20 lb), a suitable child seat to 18 kg (40 lb), and a booster until the child reaches about 145 cm (4 ft 9 in) or a set age or weight: for example Ontario 8 years or 36 kg, British Columbia 9 years, Alberta has no booster law and requires a seat under 18 kg and 6 years. Nova Scotia and Prince Edward Island add a 1 year and 10 kg rear-facing minimum. Each province's rule is shown after you calculate.
Best practice. The American Academy of Pediatrics recommends rear-facing as long as possible up to the seat maker’s highest weight or height limit, then a forward-facing seat with a harness up to its limit, then a belt-positioning booster until the vehicle seat belt fits properly, typically at 4 ft 9 in (145 cm) and age 8 to 12, and children under 13 in the back seat. Because this tool does not know your seat’s limits, it shows the stage by size and tells you to follow the label.
Pounds convert at 0.4536 kg and inches at 2.54 cm.
Sources and basis: Parachute, Car Seat and Booster Seat Canadian Legislation Chart (parachute.ca, information purposes only; checked 2026-10-05); Alberta Health Services, Alberta Child Safety Seat Guidelines (myhealth.alberta.ca, checked 2026-10-05); American Academy of Pediatrics, Car Safety Seats: Information for Families (HealthyChildren.org, updated 2026-04-16). Check your provincial transport ministry for the current law.
FAQ
When can my child face forward?
Keep your child rear-facing until they reach the rear-facing weight or height limit on the seat. Canadian provinces set minimums (usually 9 kg and in some provinces 12 months), but safety groups advise staying rear-facing longer.
When can my child use a booster seat in Ontario?
A booster is needed once your child has outgrown the harness, and is required until they reach 145 cm (4 ft 9 in), 36 kg (80 lb) or 8 years, whichever comes first.
When can my child stop using a booster?
When the vehicle belt fits: the lap belt low across the upper thighs, the shoulder belt across the chest and the child can sit that way the whole trip. That is typically around 145 cm and age 8 to 12.
Does this cover US state laws?
No. Choose United States for best-practice guidance only. State laws differ, so check your state’s rules.
What age can my child sit in the front seat?
The AAP recommends all children under 13 ride in the back seat.