Methodology & sources
We'd rather you trust this than take our word for it. Here is every input, what we do with it, and where it's weak.
What we pull from NHTSA
- Car-seat ratings & limits — the NHTSA childSeats API: every seat's type, the per-mode child weight & height limits, LATCH (lower-anchor) weight limits, recall count, and the 5-star Ease-of-Use ratings. This is the neutral, cross-brand backbone — and it's government data no content farm can fabricate. Last pulled 2026-06-17 16:29 UTC; we currently track 25 seats.
- Stage guidance — NHTSA's Car Seats & Booster Seats recommendations (rear-facing → forward-facing → booster → seat belt), reproduced below.
- Vehicle enumeration — NHTSA's vPIC database, the canonical year/make/model list used to validate our vehicle catalog (19 vehicles).
What we add (and where it's approximate)
NHTSA publishes how a seat fits a child, but not its external width, and nothing about a specific car's back seat. Those are the physical-fit inputs, and we are honest that they are the soft part of this:
- Seat external width — manufacturer published specifications, at the widest point. This drives three-across. Cited on every seat page.
- Vehicle usable rear-bench width — compiled from manufacturer interior dimensions and owner measurements. These vary by trim, year, and how you measure, so they are approximate. We round conservatively and tell you to test-fit on every page.
- Rear-facing legroom flag — a heuristic for short-wheelbase cars where a deep rear-facing seat may crowd the front passenger. It's guidance, not a measurement.
What we compute
- Stage — your child's age, height, and weight → the NHTSA-recommended mode.
- Child fit — your child's numbers checked against each seat's NHTSA-published limits for that mode.
- Vehicle fit — seat width × 3 vs the car's usable bench (three-across), plus the rear-facing legroom flag.
- Ranking — among seats that fit, highest NHTSA Ease-of-Use first; ties broken by fewer recalls, then narrower, then lower price.
What this is NOT
We do not crash-test seats (no one rates individual seats for crash performance — not even NHTSA). We do not certify fit or installation. We are not affiliated with NHTSA or any manufacturer. Our recommendations are a computed starting point; the seat and vehicle manuals, and a hands-on test-fit, are the authority. When in doubt, a free car-seat inspection station will check your install in person.
NHTSA stage guidance (verbatim intent)
Rear-facing
Birth until at least age 2, and ideally until the child reaches the top height or weight allowed by the rear-facing limits of their convertible seat. Rear-facing is the safest position for the head, neck, and spine in a crash.
Forward-facing harness
After outgrowing rear-facing, in a forward-facing seat with a 5-point harness and top tether, until reaching the top height or weight the harness allows — typically around age 5, but keep using the harness as long as the child fits.
Belt-positioning booster
After outgrowing the forward-facing harness, in a belt-positioning booster so the adult lap-and-shoulder belt fits correctly, until the seat belt fits without a booster — usually when the child is about 4 feet 9 inches tall, between ages 8 and 12.
Adult seat belt
Ready for the adult seat belt alone when the lap belt sits low across the upper thighs (not the stomach) and the shoulder belt crosses the middle of the shoulder and chest — and the child can sit all the way back with knees bent at the seat edge. All children under 13 ride in the back seat.
Data vintages — NHTSA car-seat ratings: 2026-06-17 16:29 UTC; vehicle catalog: 2026-06-17 16:29 UTC. Informational only — built from NHTSA public car-seat ratings and published seat/vehicle dimensions. This is not a safety certification and not a substitute for the seat and vehicle manuals. Always confirm the fit and install yourself before every trip.