Under Californian law, children under the age of two must use a rear-facing car seat. Once a child is over the age of two, weighs more than 40 lbs (around 18 kg) or is taller than 40” (around 102 cm), they can use a forward-facing car seat or booster appropriate for their age and size. This requirement holds until a child is eight years old or at least 4’ 9” (around 150 cm). Above this age and height, boosters are often still recommended, with a seat belt being the minimum requirement.