How to buy a convertible car seat
Ease of use: Check the National Highway Transportation Safety Administration's (NHTSA) 5-star rating system for all types of car seats. You can search convertible car seats, 3-in-1 models, boosters, and infant car seats. These ratings take into account how easy it is to install the seat in your car and secure your child in it, as well as the content and clarity of the instruction manual. The more stars a car seat has, the simpler it is to use.
Weight and height limits: The higher these are, the longer your child will be able to safely use the car seat. Also, choose a car seat with generous rear-facing height and weight limits because it's safest to keep your child rear-facing as long as possible.
Car seat weight: Convertible car seats are heavy and aren't designed to go in and out of the car easily (unlike infant car seats). If you'll need to switch your car seat between cars or take it on a plane, look for one that's on the lighter side.
Car seat size: If you have a small car or need to fit three car seats across a row, you'll need a smaller or more narrow car seat. (Here's a list of great compact car seats.)
A five-point harness: These straps – one for each shoulder, one for each hip, and one that goes between your baby's legs – are crucial for safety, and they're found on all new car seats.
Side-impact protection: Some car seats have special energy-absorbing foam and other features designed to better protect your baby's head and chest in a side-impact accident.
Easy adjustments: You'll need to adjust the harness as your child grows. Better car seats allow you to adjust the straps and harness height from the front so you can take care of this while your child is in the seat (rather than removing your child, taking the car seat out of the car, and rethreading the harness). A few models make it so easy to make adjustments, you can do it with one hand.
LATCH (lower anchors and tethers for children): The LATCH system allows you to attach the car seat directly to your vehicle's frame with anchors and tethers, which is safer and more foolproof than using a seat belt to secure it. All convertible car seats are equipped with a top tether strap and lower anchor connectors, but the manufacturer may recommend not using the top tether strap in the rear-facing position, so check the manual. Also, there's a LATCH weight limit, and when your child hits it, you'll need to install the seat with the seat belt.
Comfort: A well-padded seat with plenty of head support gives your child a better ride.
Easy cleaning: Kids and mess go hand in hand, but some car seats come with covers you can't remove easily. An easily detachable, machine-washable cover makes cleanup much easier.