Car seat fit checker: will three fit across?
Pick up to three seats and a vehicle. We add the manufacturer-published widths and compare them with the vehicle's published rear hip room — the fastest honest screen before you spend anything.
Safety notes that outrank any calculator
- Rear-face as long as possible. AAP guidance: keep children rear-facing until they reach the car seat's maximum rear-facing height or weight.
- Every seat independently tight. Each install should move less than an inch at the belt path on its own.
- Manuals win. The car seat manual and the vehicle owner's manual govern LATCH limits, tether use, and seating positions.
- Get a human check. Certified child passenger safety technicians offer free or low-cost install checks in most areas.
Seat widths in this checker
Manufacturer-published widths, checked 2026-11-12. Source dataset: gear.json in this package (per-brand copy of the verified v1.1 dataset).
| Seat | Type | Published width |
|---|---|---|
| Chicco KeyFit 35 | Infant carrier | 16.5″ |
| Graco SlimFit3 LX | Convertible (3-in-1) | 16.7″ |
| Chicco Fit3x ClearTex | All-in-one | 16.7″ |
| Clek Foonf | Convertible | 16.9″ |
| Clek Fllo | Convertible | 16.9″ |
| Clek Liing | Infant carrier | 16.9″ |
| Evenflo Revolve360 Slim | Convertible (rotating) | 16.9″ |
| Diono Radian 3R | Convertible (3-in-1) | 17.0″ |
| Britax Poplar | Convertible | 17.0″ |
| Britax Poplar S | Convertible | 17.0″ |
| UPPAbaby Mesa | Infant carrier | 17.0″ |
| Cosco Scenera Next | Convertible | 17.0″ |
| Nuna Pipa | Infant carrier | 17.5″ |
| Graco 4Ever DLX | All-in-one (4-in-1) | 19.5″ |
Vehicle rear hip room
| Vehicle | Rear hip room |
|---|---|
| Toyota RAV4 | 49.6″ |
| Honda CR-V | 52.6″ |
| Hyundai Santa Fe | 54.9″ |
| Toyota Highlander | 57.0″ |
| Subaru Ascent | 57.2″ |
| Honda Pilot | 57.4″ |
| Kia Telluride | 58.0″ |
| Honda Odyssey (2nd row) | 64.8″ |
Planning tool only — not a safety certification. Widths are manufacturer-published widest-point figures, and a combination that fits on paper can fail in a real back seat. Always test-fit and follow both manuals. Educational information only — not medical advice. Every pregnancy and every baby develops on their own timeline. If you have any concern, talk to your obstetric provider or your baby's pediatrician.