Last Updated: Dec 2, 2021 @ 1:18 pm.

What is the best 3 in 1 car seat? And what makes a seat 3 in 1 anyway? We compared 9 brands of car seats that promise to work for newborns up to older kids. Which were easiest to install? Had excellent third-party crash test results? Were easiest to use every day? Here are the ones we would recommend. FYI: We've been reviewing and rating products for the babies, families and the home since 1994. We don't take money or freebies from the brands we review. Our work is 100% reader-supported!


Best Budget-Friendly

Safe, tight fit
Easy is the star feature here—this seat is easy to install, easy to adjust and easy to use. We love the cup holders. Bonus: narrow width is great for smaller vehicles.

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Best Budget-Friendly: Graco SlimFit

Let’s talk 3 in 1 car seats.

When a seat says it is a “three in one,” that means it works through the three main stages of your baby’s development: newborn, toddlers and booster age:

• Newborn: Here your baby rides rear-facing in a five-point harness until the limits of the seat (usually 40 lbs., but some seats now work up to 50 lbs.).

• Toddler: Once your baby outgrows the rear-facing limits, you turn the seat forward facing and use the five-point harness.

• Booster: These are for older kids, where the vehicle’s seat belt replaces the built-in five-point harness. The seat becomes a belt-positioning booster, which makes sure your vehicle’s seat belt is correctly positioned across a child’s body. The seat also provides side impact protection.

In the old days, these three stages had three distinct seats: infant, toddler (also known as convertible), and booster.

Three in one seats combine all three functions into one seat. Or at least that is the promise!

Since you aren’t paying for three separate seats, you would think three-in-one seats would be less expensive. Yet some can get very pricey . . . but there is good news: we found one model that is easy to use, simple to install and doesn’t burn a hole in your bank account—the Graco SlimFit.

This seat scored well in third-party crash tests and overall ease of use in our research . . .  at a price that doesn’t break the bank.

Yes, this seat is a 3 in 1—it is used for infants (rear-facing to 40 lbs.), toddlers (forward-facing (22-65 lbs.) and older kiddos as a belt-positioning booster up to 100 lbs. Here are the pros and cons:

What We Liked

• Integrated harness and 10-position headrest. As you move the headrest higher, the harness adjusts with it—no need to rethread the harness and fit it through harness slots.

Narrow. The Graco SlimFit is just 17″ wide (with the cup holders folded in). Hence, this seat may work better in smaller vehicles—or if you need to install three seats across a back seat for a carpool.

• Affordable. With some new car seats priced like they are pulled from a hotel mini bar, it’s nice to find a safe, well-designed seat that is affordable.

What Needs Work

• Limited recline. There are just four total recline settings (two for rear-facing, two for forward-facing). While we found this acceptable in our testing, we realize some folks may want more recline positions.

• Doesn’t convert to a backless booster. Some “all-in-one” seats convert to backless boosters for older kids up to 120 lbs. The SlimFit only works to 100 lbs. as a belt-positioning booster.

Best Extended Use

Tried & true brand
One car seat to rule them all! We liked the side-impact protection and ease of install. Also great: carry handle, no rethread harness and yes, there are cup holders! Caveat: harness covers are thick.

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Best Extended Use: Britax One4Life

Just to confuse you, some three-in-one seats are also called all-in-one car seats. This one, the Britax One4Life, is excellent for extended use. 

That’s because it not only works for infants and toddlers, but also older kids up to 120 lbs. That’s 20 more pounds than the Graco SlimFit we recommended above.

Also nice: Britax One4Life enables you to do extended rear-facing use, since it can be used rear-facing up to 50 lbs. The Graco SlimFit, as with most other car seats, is only rear facing to 40 lbs.

Safety advocates recommend keeping your child rear-facing as long as possible, since it is safer in an accident. 

Known for its best-selling line of convertible car seats, this is Britax’s first effort in the all-in-one car seat category—a seat for newborns, toddlers and older kids up to age 10.

Britax is a tried-and-true car seat brand . . . we like their overall reputation and commitment to safety testing and design.

So what makes the Britax One4Life so splurge-worthy? Here’s a look:

What We Liked

• Extensive side-impact protection. Britax was one of the first car seat brands to bring extensive side-impact protection to the US—and this seat continues that trend with two layers around the head, neck and torso. (Less expensive seats just use side-impact protection in the headrest).

Simple install. This seat has Britax’s ClickTight installation—in our tests, we found this system easier to use than competing brands. Impressive, rock-solid installations.

• 9-position recline. Less expensive seats may only have one or two recline positions—the One4Life lets you dial among nine different choices.

• No added flame retardants. The One4Life has a “SafeWash” cover that can be machine washed and dried.

• Premium features: harness covers, 15-position headrest, fancy/comfy fabrics and more. Bonus: you can use this seat up 120 lbs. as a belt-positioning booster for older kids.

What Needs Work

• Pricey. 

Heavy. At nearly 30 lbs., this seat won’t be easy to lug from car to car. If you need a car seat for carpools, this probably isn’t the best bet.

Best Gift Idea

Easy to buckle
Excellent side impact protection is the headline here—but we also think the premium fabrics and padding make it worth the investment. And yes, you even get two built-in cup holders.

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Best Gift Idea: Maxi-Cosi Pria Max 3-in-1 Convertible Car Seat

Like most baby gear, convertible car seats can be generally divided into two categories: utilitarian seats that are great for everyday use and premium models that have more bells and whistles. 

We know when considering a gift for a grandchild or baby shower, some folks want all the premium features of a top-of-the-line seat. We looked at several top-end 3 in 1 seats before deciding Maxi-Cosi is the best bet for most folks.

We liked this seat’s side-impact protection (Air Protect) and covers that are easy to remove. The star feature, however, is probably the premium fabrics and oodles of padding . . . this seat looks sharp and will certainly make an impression at that baby shower.

The extended use of this seat (it can be used for infants, toddlers and then as a booster to 100 lbs.) is another major feature that separates it from lower-end seats.

What We Liked

Soft, plush cover.

• Side impact protection.

• Converts to booster mode for use up to 85 lbs.

• Rear facing to 40 lbs.

• Lighter in weight compared to other seats in this category, making it somewhat easier to move from vehicle to vehicle.

What Needs Work

• No lock-offs for belt installations. That means you’ll have to understand how to lock your vehicle’s seat belts when installing. This isn’t impossible, but just an extra step compared to other seats with lock-offs.

• LATCH connectors may be too short for some vehicles.

• Large seat size may not fit well in smaller vehicles.

• Must use a tether in forward-facing position.

• Pricey. 

Best Tried & True Brand

Quick remove fabric for cleaning
This seat scores high on our easy-to-use and easy-to-adjust ratings—and the extra fourth stage of use (backless booster). And did we mention the built-in cup holders?

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Best Tried & True Brand: Graco 4Ever DLX

If you want to go with a brand that has high parent satisfaction and a good safety track record, the Graco 4Ever DLX is an excellent choice.

This seat has one trick that the other car seats in this article lack: it converts to a backless booster for older kids.

So, yes, this seat has four stages: infant, toddler, booster and backless booster.

Graco clearly has put a lot of thought into the 4Ever. Little touches like the harness that stores away in booster mode (you don’t have to remove it from the seat) are very nice.

What We Liked

• Super easy to install.

• Converts to backless booster.

• Easy-to-remove pad to wash.

• Easy to adjust as child gets bigger.

What Needs Work

 • In rear-facing mode, the seat’s harness can be tricky to tighten.

• The lack of a belt lock-off for seat belt installs is a curious omission for a seat in this price range.

• Minor quibble: there is a level indicator, but only on one side. 

Why Trust Us

We’ve been rating and reviewing products for the home and families since 1994. We do extensive research, evaluating products with an eye toward quality, ease of use and affordability. When we purchase a product for hands-on testing, we do so with our own money.

Here’s another key point: we don’t take money from the brands we review. No free samples, no sponsors, no “partnerships.” Our work is 100% reader-supported!

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