Last Updated: May 4, 2023 @ 10:41 am.

What is the best slim car seat? You know, a car seat that can fit into a small back seat area? We surveyed our parent readers for their real world suggestions. Then we did 8 more hours of research, comparing over 11 different models. Which slim car seats are best for infants? For older kids? Here are the ones that made the cut.

FYI: We've been reviewing and rating products for the home and families since 1994. We don't take money or freebies from the brands we review. Our work is 100% reader-supported!

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Best Slim 3-in-1 Seat

Easy to adjust
We liked this seat from a tried and true brand that has a good quality reputation. Easy to use, with impressive leg room for older kids.

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Best Slim 3-in-1 Seat: Graco SlimFit

Let’s talk slim car seats.

After writing about this topic for 30 years, you quickly realize one truth about car seats: they keep getting bigger and bigger.

While that is good in a way (better side impact protection for example), all that padding and safety can take up a good amount of real estate in a vehicle back seat.

That might be ok if you drive a large SUV . . . but what if you don’t? If are looking for a car seat with a small footprint, you came to the right article. We measured over 25 different seats then narrowed those down to the 11 slimmest seats. Next we asked our parent readers for their favorites. We also compared crash test data from third party sources.

When it came to the best 3-in-1 car seat (infant, toddler and older kid), the winner is the Graco SlimFit.

This seat scored well in crash-testing and overall ease of use at a price that doesn’t break the bank.

This seat is a “3-in-1″—that is, 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.

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Best For Carpools

Steel frame adds to safety
The star feature is the fold—yes, this seat folds up, so it can easily be moved from vehicle to vehicle. Easy to install and use.

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Best Slim Car Seat For Carpools: Diono Radian 3R

The narrow base of this car seat (just 17″) enables you to fit three across in most vehicle back seats—that is a big boon for carpools. Overall, we like the Diono brand, which has a good quality and safety reputation.

What We Liked

• Steel frame adds to safety.

• Easy to install.

• Folds up.

• Machine washable cover.

• 3-in-1 use with high back booster mode for older kids.

• Can fit three across in most vehicles.

What Needs Work

• A bit pricey.

• Padding could be a bit more generous.

• No head support for napping infants.

• No cup holder.

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Best For 2 Year Olds

Comfortable padding
We liked the bang for the buck here—many high end features (one-hand adjustment for harness) at a price that is easy on the wallet. Narrow 17.4" base means it fits in tight spaces.

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Best Slim Car Seat For 2 Year Olds: Graco Tranzitions

Safety experts agree: it is safest for babies and young toddlers to ride rear-facing until age 2. But after that, what’s the best car seat?

To answer that question, we looked at the current crop of front-facing car seats (we’ve been reviewing and rating car seats for 25+ years). Then we asked our parent readers for their real-life experiences. Finally, we interview car seat techs regularly for their insights—which seats are easiest to install in the real world, for example.

After all that research, we pick the Graco Tranzitions 3-in-1 Harness Booster Seat as the best slim car eat for 2 year olds. One big reason: that five-point harness. While a two year old may think they are a big kid (and no one can argue with a toddler), the five-point harness keeps them in place during vehicle rides—and that’s safer.

What We Liked

• Lightweight—it’s easy to move from vehicle to vehicle.

• One-hand adjustment for harness and headrest.

• Dual cup holders.

• Works up to 65 lbs. in harness mode; 30-100 lbs. as a booster—then morphs into a backless booster up to 100 lbs.

• Side-impact tested.

• 8-position headrest allows for growing child.

• Machine washable seat pad.

• Comfortable.

• Can be used on an airplane (with harness only).

What Needs Work

• Armrests could be bigger.

• Buckle button can be hard to press for younger toddlers. Toddlers love their independence, so a few may be frustrated that they require a bit of strength to release the button on their own.

• No seat recline.

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Best Budget-Friendly

Removable cup holder is a plus
This seat is easy to install and move between vehicles. We liked the five-point harness, although the padding is minimal.

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Best Budget-Friendly: Cosco Finale DX 2-in-1 Booster Car Seat

If you are looking for a slim booster car seat that doesn’t break the bank, we would suggest this model by Cosco: the Finale DX. It is simple to use and lightweight, making it a good bet for carpools. And yes, there is a removable cup holder. Best of all, the price is easy on the wallet.

What We Liked

• Easy to install.

• Lightweight.

• Can fit three across in most vehicles.

• Cup holder is removable.

• Machine washable pad.

• Sturdy design.

• Affordable.

What Needs Work

• Seat padding is minimal.

• Straps don’t have any harness pads.

• Not as ideal for taller kids, in our opinion.

• Base at 18.25″ is a touch wider than other seats in this article.

About the Authors

Denise & Alan Fields are consumer advocates and best-selling authors. The Fields have authored 12 books with three million copies in print, including the best-selling guide to baby gear, Baby Bargains.

The Fields have been featured and quoted in the New York TimesWall Street Journal and Los Angeles Times.

As consumer products experts, the Fields have been guests on the NBC Today Show, Good Morning America and ABC’s 20/20.

How We Pick Products To Recommend

We often turn to our readers (3 million strong!) to find products to recommend. We ask our parent readers for their favorites and consider their real-world experiences in our recommendations.

When we test a product, we always purchase it with our own monies. We do not take free samples, as we believe that compromises our independence.

We also fact check manufacturer information with our own measurements. If a maker claims a product weighs X pounds, we will weigh it to make sure. If the battery life is supposed to be six hours, we will see how it stands up in the real world.

In some cases, we will do interviews with experts in the field to get additional feedback on products.

To get hands-on time with products, we regularly meet one-on-one with gear companies and even tour manufacturing facilities. (When we do this, we pay our own travel expenses).

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.

We make our living from affiliate commissions, but we always recommend what we think are the best bets for our readers (not the ones that are the most expensive). We are always looking for products that offer the best bang for the buck.

Our independence is a key reason why we have been doing this so long. As we mentioned above, 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!

Best Slim Car Seat

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