Best Convertible Car Seats

Britax convertible car seats top others

Britax convertible car seats get the best scores in car seat reviews, though they're also the most expensive. The Britax Marathon (*Est. $280), Marathon CS (*Est. $280), Decathlon (*Est. $275), Boulevard (*Est. $310), Boulevard CS (*Est. $330) and Advocate CS (*Est. $350) are considered full-sized convertible seats; Britax calls the Roundabout (*Est. $190) and the Diplomat (*Est. $260) "compact convertibles." There's also the Roundabout 50 (*Est. $200), which Britax dubs a "mid-capacity convertible." All are similar, but differ in features, weight limit and upholstery. All Britax convertible car seats have hand-washable seat padding and a five-point harness.

Click and Safe (CS), is a new option available on the Marathon and Boulevard. (The Advocate is available only in CS.) Otherwise identical to the corresponding base models, these car seats have a modified harness adjuster that clicks audibly when the harness is snug enough. Reviewers say there's nothing wrong with the added feature, but most say it's an unnecessary extra given that, with a little practice, parents can do just as good a job of judging harness fit themselves.

The least expensive Britax convertible car seat, the Britax Roundabout (*Est. $190), has long been a favorite in car seat reviews, and in crash testing it performs extremely well. The Britax Roundabout may be tethered either in the front- or rear-facing position; not all car seats can be used with a tether in the rear-facing position. The Roundabout also has a layer of EPS padding (the material used in motorcycle helmets) to absorb shock during a collision and a five-point harness with up-front adjustment. On the negative side, the Roundabout is expensive, and some parents say that it is too bulky for their smaller vehicles.

A few parents posting to opinion websites say their taller-than-average children outgrew this seat relatively quickly. Overall, however, parents say the high price is worth it, and reviewers say the Roundabout is an easy-to-use, comfortable car seat. The Roundabout can be used in the rear-facing position for newborns and infants up to 35 pounds. When in the front-facing position, the Roundabout is rated for a child that's up to 40 pounds and 40 inches tall. The seat itself weighs about 13 pounds.

The Roundabout 50 (*Est. $200) extends the weight limit to 50 pounds and the maximum height to 49 inches. It also has multiple buckle positions in common with the more expensive Britax Decathlon. Otherwise, it has the same features as the basic Roundabout.

Like the Britax Roundabout, the Britax Marathon (*Est. $280) is rated for babies up to 35 pounds in the rear-facing position, but when it faces forward, it can be used by kids until they weigh 65 pounds. This makes the seat larger and heavier than the Roundabout. Many parents with smaller vehicles complain that the car seat is simply too large for their cars, so if you have a compact car like a Honda Fit or Toyota Yaris, you might want to check out the compatibility database at CarSeatData.org (see our Useful Links section) and try the seat in your own car before you commit. Most owners say their children are comfortable in the Marathon, but a few complain about overly tight crotch straps and insufficient recline. Overall, the Marathon is similar in features to the Roundabout.

The Britax Decathlon and Boulevard are evolutions of the Marathon, and both are rated for children up to 65 pounds in the front-facing position. The Britax Boulevard (*Est. $310) has some additional foam along the inner sides of the car seat for added head protection in a side-impact crash. The side-impact padding is height-adjustable to accommodate growing children. There's also an additional belly pad and an inner infant liner so that babies fit more snugly in the seat. This extra padding is removable. The Boulevard car seat has frontal adjustments to tighten the harness, plus a new knob for adjusting the height of the shoulder straps without having to rethread them as your child grows.

The Britax Decathlon car seat (*Est. $275) costs a little less and has similar features, including an infant pad, belly pad, side-impact protection foam and front harness adjustment. The side-impact foam adjusts height-wise. There are also three positions for the crotch belt, so it can be positioned closer to or further away from baby. For children too short or too young for a toddler seat, but who have exceeded the weight limit of most other convertible car seats, the Britax Marathon, Decathlon and Boulevard are options.

The Britax Diplomat (*Est. $260) is one of the newer Britax convertible car seat. The Diplomat has the same height and weight limits as the Roundabout (rear-facing from 5 to 35 pounds and forward-facing to 40 pounds or 40 inches) and comes with side protection, a multi-position headrest, a no-thread harness and an infant body pillow. Like the Decathlon and the Roundabout, the Britax Diplomat car seat has push-button harness adjustment instead of a lever. Parents are generally happy with the Diplomat. Owners say Britax's latest convertible car seat fits nicely into smaller cars, leaving plenty of room in the driver and front passenger seats.

A more portable alternative to the Britax car seats is the Sunshine Kids Radian65 (*Est. $215). The Radian65 is a foldable, high-capacity convertible car seat that parents say fits easily even in smaller cars. As the name suggests, the Radian65 is rated in the forward-facing position for children up to 65 pounds. Rear-facing, it accommodates kids weighing up to 40 pounds. The similar Sunshine Kids Radian80 (*Est. $240) extends weight limits to 80 pounds forward-facing and 45 pounds rear-facing. Since the height limits are the same on both seats -- 53 inches -- taller children may not benefit from the extra weight capacity. The newer Sunshine Kids Radian XT (*Est. $270) has the same specs as the Radian80, but adds a height-adjustable headrest and deeper side-impact protection.

One feature that sets the Radian convertible car seats apart is that they are foldable. That makes them easier to transfer between vehicles or to bring along on airplanes or taxis. They're also narrower than other high-capacity convertible car seats since they have a steel alloy inner structure rather than plastic, making them a better fit in some cars. Despite its narrower profile, some parent reviewers say the Radian still isn't a good fit in their cars. Others complain that, at a minimum of 23 pounds, (26 pounds for the heftier XT), they're too heavy to carry around even with the optional carry strap. A popular remedy is to use a wheeled cart or pop the folded car seat into a stroller. Some parents find the crotch straps too restrictive for heavier children, but Radian does carry an optional longer center buckle strap (*Est. $8). Ease-of-use ratings are mediocre according to NHTSA, although most of the demerits revolve around poor labeling. While the Sunshine Radian car seats don't work for everyone, they are filling a niche for heavier children who still require a five-point harness.

For slightly less than the Britax and Radian seats, The First Years True Fit (*Est. $180) earns nearly equivalent ratings from some respected sources. Heather Murphy at CarSeatBlog.com and Hollie Schultz at BabyGizmo.com both include it -- along with the ubiquitous Britax seats -- in their lists of the best convertible car seats. The True Fit has high-end convenience features like up-front adjustment, multi-position crotch strap and impact-absorbing EPS foam. User reviews are generally positive as well, but some reviewers do report difficulty with installation and rear-facing adjustment.