Here's what you must know about car seat requirements for your child: Rear-facing Your baby must be kept in a rear-facing seat until he turns 1 and weighs at least 20 pounds. But if he reaches the car seat's weight limit before he's 1, he must ride in a rear-facing convertible seat. Many parents prefer the convenience of an infant carrier because the seat can be removed from the car without having to unstrap the baby. The car seat base remains strapped into the vehicle; the carrier simply snaps in and out of the base. Convertible These seats allow an infant to ride in the rear-facing position from birth until he turns 1 and weighs at least 20 pounds. The seat can then be turned to the forward-facing position until the child weighs about 40 pounds (weight limits vary by model). Forward-facing These seats are designed for children who are 1 or older and weigh 20 pounds or more. Some forward-facing seats convert to belt-positioning boosters when a child reaches about 40 pounds. Booster seat These forward-facing seats are for children 4 to 8 years old, weighing 40 to 80 pounds, and are required by law in some states.