A child seat is bought for a back seat, and the back seat is the part of a vehicle that changes most from one model line to the next. Width, depth, cushion shape, anchor position, and the way a door swings can each decide whether a seat that works in a store works in the driveway. This guide is for the household that has a seat in hand or on order, and a car that is already in the drive or on the list.
Measure the space the seat will use
Measure from the back of the front seat, with the front seat set where the driver would sit, to the back of the rear seat. Then measure the width of the seating position at the cushion and at the backrest, because many rear seats narrow toward the middle. Write both measurements down next to the seat dimensions printed on the box or the maker's site. Do not compare a measurement from memory with a figure on a sales page.
Read the vehicle manual before the seat
The owner's manual has a section on child restraints. It names the seating positions that accept a child seat, the location of any lower anchors, and whether a top tether anchor is provided at each position. Some positions that look wide enough have no anchor, and some have an anchor but a sloped cushion that tilts a rear-facing seat. If the manual is not in the glovebox, the vehicle maker's site or the dealer's service desk can supply it. Ask for the page on child restraints by name.
Test the install in the car, with the seat the household will use
A demonstration in a store is not a test in your vehicle. Take the seat to the car and install it in the position it will occupy. Check that the belt or anchor holds the base firmly, that the seat sits at the angle the maker's instructions describe, and that the front seat can move far enough for a rear-facing seat to sit without pressing against the front seat back. Then check the buckle and the door opening. A seat that installs well can still be hard to load a child into if the door opening is narrow or the buckle sits low under the cushion.
Check the seats that share the row
If the household will carry more than one child seat, or a child seat beside an adult passenger, test the whole row with every seat in place. Seats that fit side by side on paper can crowd each other once installed, and a seat in the middle may be the only place another seat fits. Note which positions the manual allows for each seat type, because a position that accepts a seat with a top tether may not accept the same seat without one.
Ask the seller before the purchase
Ask whether the seat can be returned after it has been installed, and whether the return window starts at purchase or at delivery. Ask whether the seat can be exchanged for a different size if the install fails. Keep the packaging until the install is confirmed, and keep the instruction sheet with the vehicle paperwork so that anyone who drives the car later can find the rules for the seat.
Check the seat and the vehicle against federal records
Look up the seat's model and its manufacture details against the federal recall records for child restraints. Then look up the vehicle line against the federal records this site publishes for each model, where they have been published. A recall notice and a complaint entry are different federal records. Read the notice itself before reading any count printed beside it, because a count shows how many reports exist and does not show how often a problem occurs.
Where this site fits
Use the brand drawers to find the vehicle brand, and the model index to find the card for the line. Open the year row to reach the library page for that year, where the tables and any federal blocks are kept. The lists section gives the terms that manuals and recall notices use, and the method page explains how each record is built. This guide does not say which vehicle or seat suits a household and does not rank either one. The fit is a measurement, a manual, and a test in the car.