Car Seats

Car seats come in three shapes, and you will own at least two of them.

Infant seats carry from birth. They detach from a base, which is the feature you will use most: a sleeping baby comes out of the car still asleep and clips onto a stroller. You outgrow them on height, usually between nine and fifteen months, long before the weight limit printed on the box.

Convertible seats start rear-facing and turn around later. They stay in the car. One seat covers roughly birth to four, and the specification that separates them is the rear-facing weight limit: 40 lb and 50 lb are about a year apart in practice.

Boosters come last, once the harness is outgrown, and position the adult seatbelt correctly across a child's body.

When to switch

Out of the infant seat on height, not weight: the head within an inch of the top of the shell.

Out of rear-facing as late as the seat allows. Rear-facing spreads crash force across the whole back and supports head and neck together. Bent legs are not a problem; children sit cross-legged happily and leg injuries in rear-facing crashes are rare.

The number that catches people out

LATCH anchors are rated for 65 lb of seat plus child combined. A convertible weighs 20 to 34 lb, so you hit the ceiling around 35 lb of child and must switch to a vehicle seatbelt install from then on.

That is why we score the two installation methods separately rather than averaging them. A seat that fits brilliantly on LATCH and awkwardly on a belt has a problem that arrives on your child's fourth birthday.