When do you start to use booster seat with your child?

Your child is ready for a booster seat when they have outgrown the weight or height limit of their forward-facing harnesses, which is typically between 40 and 65 pounds. Read your forward-facing car seat’s owner’s manual to determine height and weight limits, and keep your child in a harnessed seat for as long as possible. Children at this stage are not yet ready for adult safety belts and should use belt-positioning booster seats until they are at least 4’9″ and between 8 and 12 years old. Safety belts are designed for 165-pound male adults, so it’s no wonder that research shows poorly fitting adult belts can injure children.

Your child's weight is usually the best guide to deciding when to use a booster seat. If your kid is over 15 kgs she can be in a booster seat and continue to be in it till she is 36kgs. A large number of kids reach this milestone around their 4th birthday. However if your child still fits comfortably in the car seat, which means her shoulders are below the top set of harness-strap slots in the car seat's back -- carry on using the car seat.

Typically a booster seat is meant for children ages four to eight (or 19kg to 36kg). Depending on the development on your child, you can decide when is a good time to use it. One of my colleagues started using a booster seat for her daughter when her girl was five and couldn't fit into her car seat (but has yet to reach 1.35m in height).

You can safely switch your child to a booster seat if she's at least 4 years old and she weighs about 20 KG or more or has grown too tall for her car seat (when her shoulders are higher than the top set of harness-strap slots in the car seat's back).