Radian 3QX › fit in › Toyota Sienna
Will the Diono Radian 3QX fit in a 2011–2020 Toyota Sienna?
Yes — the Diono Radian 3QX fits a 2011–2020 Toyota Sienna.
The Radian 3QX is about 17" wide; the Sienna's usable rear bench is about 54". It fits one rear position comfortably. Three even fit across the back (51" needed vs 54").
The Radian 3QX is about 17" wide; the Sienna's usable rear bench is about 54". It fits one rear position comfortably. Three even fit across the back (51" needed vs 54").
17"Radian 3QX width
54"Sienna rear bench
Yesthree across
★★★☆☆NHTSA Ease-of-Use
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What fits this Sienna
- One seat, rear position: Yes. The Radian 3QX installs in an outboard rear position of a 2011–2020 Toyota Sienna with room to spare.
- Three across: Yes — three need ~51" against a ~54" bench. Test-fit; three-across is decided by half-inches.
- Modes this seat covers: rear-facing → forward-facing → booster.
- LATCH: lower anchors up to 40 lb; the Sienna has 3 lower-anchor positions.
ℹ️ 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. The Radian 3QX's width (Diono published spec (steel-framed, 17 in)) and the Sienna's rear-bench width (Toyota dimensions + owner measurements (approx)) are both approximate — confirm with a test-fit before buying.
Common questions
Will the Diono Radian 3QX fit in a 2011–2020 Toyota Sienna?
Yes — the Diono Radian 3QX (17" wide) fits a single rear seating position in a 2011–2020 Toyota Sienna. Three of them also fit across its roughly 54" rear bench.
Can you fit three Radian 3QXs across a Sienna?
Yes — three Radian 3QXs need about 51" and the Sienna's usable bench is about 54". It's close, so test-fit before buying.
Sources: seat ratings & modes — NHTSA (pulled 2026-06-17); dimensions — manufacturer specs and owner measurements. 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.