Why this calculator asks for seat limits: a generic age-only calculator can tell you the broad stage, but it cannot know when your exact seat is outgrown. This one stores your child profile and lets you enter the manual limits that control the real decision.

Which car seat type does my child need?

Create a local child profile. Nothing is sent anywhere; the information remains in this browser unless you export it.

Local-only profile

Profile name

Age — years

Extra months

Weight (lb)

Standing height (in)

Current mode

Your current seat’s relevant limits

Rear-facing max weight

Rear-facing max standing height

Forward-facing harness max weight

Forward-facing harness max height

Booster minimum weight

Booster minimum age (if manual specifies)

Import JSON

Your result will appear here, with the checks that still need to be made in the manual.

How the calculator decides

The calculator uses a hierarchy rather than a single birthday cutoff. First, a child under 1 remains rear-facing. After that, rear-facing remains the preferred stage while the child still fits the rear-facing limits of the seat. When that mode is outgrown, the next stage is a forward-facing harness with a top tether, used until the harness mode is outgrown. Then comes a belt-positioning booster, which is used until the vehicle belt fits correctly without it.

For booster use, the child also needs to be able to sit properly for the entire ride. A calculator cannot measure maturity, so it never turns a weight or birthday into an automatic “booster ready” result.

What “fits” means

A numeric limit is only one piece of fit. Many manuals also specify head clearance, ear position, harness routing, crotch-buckle position or a required headrest location. If a seat says the child must have one inch of shell above the head, for example, a child can outgrow the mode before reaching the printed standing-height maximum.

That is why the result uses phrases such as “entered limits have not been exceeded” rather than claiming that a seat is safe for a particular child. The manual and physical fit check remain decisive.

Why save a profile?

Once saved, the same age, weight and height can prefill the size chart and provide context in the harness and booster tools. The data uses browser localStorage, so there is no account, server database or tracking endpoint involved. Exporting JSON gives you a tiny backup file you can move to another browser.

When to re-run it

after a growth spurt;
when a child is approaching a stated limit;
when moving the seat to another vehicle;
before changing from rear-facing to forward-facing;
before changing from a harness to a booster;
before removing a booster entirely.

Sources & verification

Use this page as a planning aid, not a replacement for the manuals. Child restraints and vehicles have model-specific requirements. Verify your child restraint manual, vehicle owner's manual and current manufacturer guidance before installation.

Safety guidance reviewed September 23, 2026.

Car Seat Calculator: Which Type Does My Child Need?