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3 across in a Subaru Impreza

At roughly 49" of usable bench, the Impreza is right on the edge. Three standard convertibles will not go; three of the narrowest (~17") seats can, edge to edge, with nothing to spare. This is the definition of a test-fit-first car.

The narrowest seats we track — closest candidates for a 2017–2021 Subaru Impreza

No seat we track clears three-across a 2017–2021 Subaru Impreza on our measurements — three of even the narrowest need about 50.7" against a 49" bench. These are the narrowest seats we have, closest first. Families do sometimes make an install like this work by half-inches and by seat order, so if you are set on this car, these are the ones to test-fit — buy from somewhere you can return it.

2

Cybex Sirona S

★★★★★ NHTSA Ease-of-Use rotating 1–2 across Slim (≤17.5") rear-facing legroom tight

A 360° rotating convertible that is unusually narrow for a swivel seat — the rare rotating pick that can still work in tighter back seats.

width 17" · covers rear-facing → forward-facing · $$$ · 3× = 51" vs 49" bench

Check price on Amazon → Full fit details Will it fit a Impreza?

3

Cosco Scenera Next

★★★☆☆ NHTSA Ease-of-Use 1–2 across Slim (≤17.5") rear-facing legroom tight

The classic featherweight budget pick — famously narrow, a go-to for fitting three across or for grandparents and travel.

width 17" · covers rear-facing → forward-facing · $ · 3× = 51" vs 49" bench

Check price on Amazon → Full fit details Will it fit a Impreza?

4

Diono Radian 3QX

★★★☆☆ NHTSA Ease-of-Use 1–2 across Slim (≤17.5") rear-facing legroom tight

Steel-framed all-in-one that holds three-across in many mid-size back seats; folds flat for travel.

width 17" · covers rear-facing → forward-facing → booster · $$$ · 3× = 51" vs 49" bench

Check price on Amazon → Full fit details Will it fit a Impreza?

5

Diono Radian 3QXT

★★★☆☆ NHTSA Ease-of-Use 1–2 across Slim (≤17.5") rear-facing legroom tight

The 3QX with quick-adjust rapid-release — same 17-inch three-across footprint.

width 17" · covers rear-facing → forward-facing → booster · $$$ · 3× = 51" vs 49" bench

Check price on Amazon → Full fit details Will it fit a Impreza?

How we worked this out

• The bench. A 2017–2021 Subaru Impreza's usable second-row width is about 49" (Subaru dimensions + owner measurements (approx)) — approximate, from manufacturer dimensions and owner measurements.
• The seats. We take each seat's external width at its widest point (manufacturer spec) and multiply by three, allowing a small buckle gap, against the bench.
• The ranking. Seats that clear three-across come first, then NHTSA Ease-of-Use (5★ scale), then fewer recalls, then narrower — never by commission.
• The honesty rule. Where a seat's width isn't published, we flag the fit as not confirmed rather than guess. Three-across is decided by half-inches, so test-fit your exact seats in your exact car.

Common questions

Can you fit three car seats across a Subaru Impreza?

Three standard car seats across a 2017–2021 Subaru Impreza (~49" usable bench) is impractical; you'd need three of the very narrowest (~17") seats and should test-fit first.

What is the best car seat for a 2017–2021 Subaru Impreza?

Among the seats we track, the Evenflo Revolve360 Slim ranks first for a 2017–2021 Subaru Impreza. The right pick still depends on your child's age, height, and weight — use the picker to narrow it.

Sources: seat ratings, modes & recalls — NHTSA (pulled 2026-06-18); seat widths & the Impreza's rear-bench width — manufacturer specs and owner measurements (approximate). 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.