L.
In general, the minimum requirement is 1 year and 20lbs, but this is just a minimum requirement. It best to leave you little one rear facing as long as possible. This means when they out grow the seat rear facing by the manufactures weight limit (usually 30 to 35lbs on convertibles, but check your manual) or the baby's head is less than one inch from the top of the seat. Most babies cannot ride in an infant carrier type seat until they reach 1 year and 20 lbs, so they need to move to a convertible carseat, one that can be placed both rear and forward facing. Keeping your baby rear facing as long as possible is safest, though. An infants neck and spine are soft and weaker than older children and adults, and their heads are very large in proportion to the rest of them, even after the one year mark. This puts them at a much higher risk for major spine injuries and even death in the event of an accident when placed forward facing too early. Studies show the risk for a child under two is more than four times greater. Unfortunately, this knowledge isn't as widespread as it should be. I really wish it were. I had never heard of such a thing when my four year old was a year old, and we turned her around right after she turned one and was still only 19 lbs. I though one lb wouldn't make a difference. I didn't know that her safety was determined by her weight, but by the strength and hardness of her spine. If you google extended rear facing, you'll get lots of info about it, even comparison videos of rear facing vs forward facing. Anyway, sorry about the novel, but hopefully I could pass on some valuable info that you or someone else reading this may not have learned other wise. We all value the safety of our children, and I'm sure this will one day be just as mainstream as the use of carseats themselves. They weren't required when I was a baby. Now you can't take your baby home from the hospital unless you have one.