Car seat calculator
Type your child's weight and height. This shows every seat whose published manufacturer limits cover those numbers, in each mode the manufacturer prints — with the manual cited. It does not rank seats or tell you a seat is safe for your child; that is decided by the manuals and a hands-on check.
Then: how to check fit in your actual car · what your state requires · how long the seat lasts
What the three different numbers mean
Almost every confusing car-seat moment comes from three numbers that do not match each other: what your seat's label allows, what your state's law requires, and what safety bodies recommend. They are answers to three different questions. The label is an engineering limit, the statute is a legal minimum, and the recommendation is neither. This calculator reads the first one only, because it is the only one printed on the object in your car.
Height or weight, whichever comes first
87 of the 106 seat-modes in this database print both a weight ceiling and a height ceiling, and a child exits the mode at whichever they reach first. Height is the one people miss, because weight is the number that gets quoted. On most rear-facing seats the printed height rule is about how much room is left above the child's head — read your manual's exact wording rather than a general rule, because manufacturers state it differently.
What this page cannot do
It cannot tell you a seat fits your car. Bench width, belt geometry, LATCH anchor placement and seat contour vary between vehicles, and no specification sheet resolves that — only a test install does. Use this to build a shortlist, then check fit properly and get the installation checked by a certified technician.
Common questions
What does this car seat calculator actually check?
Only one thing: whether the weight and height you typed fall inside the limits the manufacturer prints in that seat's manual. It does not score seats, rank them, or tell you a seat is safe for your child — those are decided by the seat manual, your vehicle manual, and a hands-on check. 53 of the 69 seats here publish limits we can cite; the other 16 are excluded and shown as excluded, never treated as unlimited.
Does a child outgrow a car seat by height or by weight?
By whichever comes first — and that is why height matters even when a child is well under the weight limit. Of the 106 seat-modes in this database, 87 print both a weight ceiling and a height ceiling. A child can be twenty pounds under the number everyone quotes and still be past the printed height. Your seat's label is the authority.
Does my state's law tell me when to move my child to the next seat?
No — a statute is a legal minimum, not a recommendation, and the two are usually different numbers. 32 of the 51 state laws we track mention rear-facing at all. Your seat's printed limits routinely allow more than your state requires. Read your state's actual wording on its state law page and treat it as the floor.
Do all states require children in the back seat?
Not remotely, and the spread is the surprising part. 30 of the 51 jurisdictions here state no rear-seat preference at all. Of the 19 with an age-based rule, the cutoff runs from 2 (Nevada) to 12 (Washington) — a six-fold difference for the same question. Check your own state rather than assuming a national rule exists.
Why are some seats missing from my results?
A seat appears only when the manufacturer publishes a numeric limit for that mode and we hold the manual citation. Missing means unsourced, not unsuitable — we would rather show a shorter honest list than guess a number onto a child-safety spec. See methodology.