Here is a handy guide to help judge how much room your child has left in his or her car seat.
So, if Junior is reaching the limits of his rear-facing convertible, the next step is forward-facing. To make the switch, make sure to read through the car seat's user manual for instructions on how to install the seat forward facing. You will need to move the seat's recline setting from rear-facing mode to forward-facing mode, and you will also need to route the LATCH belt or seatbelt through the forward-facing belt path. Also be sure to move the straps up so that they are even with or above the child's shoulder. You will also need to locate the top tether attachment in your vehicle (if your vehicle is older than 2000, it might not have one installed, but contact a local car dealership to get one installed). The car seat's top tether reduces head excursion, which means less stress is put on your child's neck and spine, so be sure to use it whether you are using LATCH or seatbelt to install the seat!