One of the most challenging and also satisfying parts of being The Car Seat Lady is figuring out which car seats will work best in tight side-by-side or 3-across situations. We’ve created a guide to help you narrow down (pun intended!) the options when you have to fit a bunch of car seats together in a small space.
We’re going to first explain why we’ve chosen the seats on this list and how vehicle geometry and car seat design interplay in this situation.
To make the list, a narrow car seat must also meet some other criteria:
Size and Shape: Size doesn’t matter (too much). Put away your measuring tape! What matters more for the car seat is how two or three car seats work together, and for the vehicle is how much usable space there is in the back seat.
For the car seat: When we choose a car seat for a three across set-up we look at the car seat’s total design, not just the width. Car seats aren’t rectangular boxes. They’re 3D objects with curves. Some sit up higher on the vehicle seat, others sit lower. Fitting 2 seats side by side is a 3D puzzle: where one car seat flares out another may be narrowest and they can puzzle together nicely. Likewise, a seat that sits low to the vehicle seat may tuck nicely next to a seat that sits high off the vehicle seat.
For the vehicle: This logic applies to the car too! The total width of the back seat doesn’t actually matter (too much). In most vehicles, there are many inches of wasted space between the door and where the seat belt is anchored. This is room that car seats can’t occupy when tightly installed. Total hip room also doesn’t matter, because very frequently the backseat is not divided up with an equal amount of space for each passenger.
Installation with the seat belt is often required for a three across set up. Why is this required if there are lower anchors in the vehicle? Lower anchors are usually centered on a vehicle seat, and as such they restrict the placement of the car seat to right in front of where the anchors are placed. When we need to put three car seats across, we usually need to use ALL the available usable space on the vehicle seat to give the center car seat enough space, which means having the car seats near the doors be slightly closer to the doors then they’d be if they were centered on the vehicle seat when installed with LATCH. If you’ve read this page regarding LATCH in the center or this page regarding locating lower anchors in your vehicle, you already know that you typically can’t use LATCH to install a car seat in the center position….which means all three car seats must be installed with the seat belt.
Because installation with the seat belt can be difficult, we favor car seats with built-in seat belt locking devices. These lock-offs usually make installation MUCH easier, which we hope leads to less misuse. These lockoffs can also make it possible to get the car seat secured in close-to-the-door positions where using the seat belt’s own locking mechanism would not provide a tight installation.
High enough height and weight limits and roominess: Some narrow seats have a very short usage due to low shell height or top shoulder strap slot. We left those off our list! All of our recommended seats are roomy on the inside even if they’re narrow on the outside. In fact, we’ve taken care to choose seats in each category that are at least as comfy, if not more roomy, than the other seats in their category that happen to be wider on the outside. Figuring out this three across situation is hard enough to do once–we don’t want you to have to do it again in 6 months when your child needs a bigger seat!
We’ve selected three infant seats that we’ve found to work in a wide variety of tight situations.
Easy and flexible installation with the seat belt: A great seat belt tensioning and locking device on the Liing’s base allows for a secure installation when positioned closer to the door than with many other seats (other seats would be loose if positioned that close to the door).
Unmistakably tight Rigid LATCH installation means you KNOW the seat is tight. If it fits, this can be super useful in a tight side-by-side or 3-across setup, because in these situations it can be harder to tell if the car seat is truly installed tightly or if it just feels tight because its wedged next to another car seat.
Visual indication that carrier is locked into base. We love this feature because it’s very helpful in a side-by-side or 3-across setup where the car seats are packed so closely together that you may not be sure that the carrier snapped in all the way.
Fits behind tall drivers. The Liing takes up less space from front-to-back compared to other infant seats, so it tends to fit better behind taller drivers or passengers. This means its more flexible in where you can install it in the vehicle–you are not limited to a behind-the-passenger position (for this reason anyway).
Easy and flexible installation with the seat belt: Thanks to the Fit2’s anti-rebound bar and built-in seat belt locking device, it often tolerates a seat belt installation positioned closer to door than do other seats. We use this car seat a lot in tight 3-across situations.
Easy LATCH installation: Smoothly pulling LATCH adjustment strap is easy to make tight.
Longevity: The Fit2 likely lasts longer than any other infant seat due to its adjustable head rest, which moves up quite high. Having a long-lasting infant seat is key to keeping your 3-across setup for as long as possible. Once the baby moves out of the infant seat, you must figure out a new 3-across combo, and who wants to do that?
Fits behind tall drivers. The Fit2 takes up less space from front-to-back compared to other infant seats, so it tends to fit better behind taller drivers or passengers. This means its more flexible in where you can install it in the vehicle–you are not limited to a behind-the-passenger position (for this reason anyway).
Center seat compatibility: The Fit2 often fits particularly well in center seats in between two forward-facing seats or boosters
Easy and flexible installation with the seat belt: Thanks to the Snugride’s Snuglock belt tensioning and locking device, this base often tolerates a seat belt installation positioned closer to the door than other car seats.
Easy LATCH installation: Smoothly pulling LATCH adjustment strap is easy to make tight.
Longevity: One of the longest lasting infant car seats. Having a long-lasting infant seat is key to keeping your 3-across setup for as long as possible. Once the baby moves out of their infant seat, you must figure out a new 3-across combo, and who wants to do that?
Fits behind tall drivers. The Snugride Snuglock takes up less space from front-to-back compared to other infant seats, so it tends to fit better behind taller drivers or passengers. This means its more flexible in where you can install it in the vehicle–you are not limited to a behind-the-passenger position (for this reason anyway).
We’ve selected two convertible seats that we’ve found to work in a wide variety of tight situations.
Fits in very tight side spaces due to seat belt installation: With built in seat belt lockoffs, a rear-facing Foonf can be placed slightly over towards the door to accommodate another car seat or passenger next to it. A seat belt installation also means there’s no need to worry about LATCH weight limits when used rear-facing.
Extremely narrow on the outside but still super comfy: This seat is narrow and streamlined on the outside but very roomy and comfy on the inside, even for bigger kids.
Fits well behind the driver or passenger: The Foonf can sit fairly upright so it’s a great choice for placement behind even a taller driver or passenger. (Older kids often prefer to sit more upright in the car) Note: Because it sits quite high off the vehicle seat, the Foonf can cause an obstructed view out the rear window when installed in the center of many vehicles, especially as a child grows and the headrest moves up.
Longevity: The Foonf can be used rear-facing until a child is 44 inches or 50 lbs. This means even a 95th percentile boy can use this seat rear-facing until his 4th birthday. The mandatory anti-rebound bar means your child will have lots of legroom.
Can be used for a newborn: The Infant Thingy, sold separately, makes the Foonf suitable for newborns. This is particularly helpful for vehicles that don’t have enough room to fit an infant seat in a 3-across set up.
Fits well in the center seat due to seat belt installation: Because it comes with built-in seat belt lockoffs, the Fllo fits very nicely in the center seat, where a LATCH installation is not usually possible. The built in lockoffs mean the seat can be placed slightly off-center to accommodate another car seat or passenger next to it. A seat belt installation also means there’s no need to worry about LATCH weight limits when used rear-facing.
Extremely narrow on the outside but still super comfy: The Fllo is narrow and streamlined on the outside but very roomy and comfy on the inside, even for bigger kids. Great for installation next to other car seats and when used in the center, usually allows both front seats to come all the way back.
Longevity: The Fllo can be used rear-facing until a child is 44 inches or 50 lbs. This means even a 95th percentile boy can use this seat rear-facing until his 4th birthday. The anti-rebound bar is optional, but when used will give your child a lot of legroom.
Can be used for a newborn: The Infant Thingy, sold separately, makes the Fllo suitable for newborns. This is particularly helpful for vehicles that don’t have enough room to fit an infant seat in a 3-across set up.
We’ve selected five forward-facing 5-point harness car seats that we’ve found to work in a wide variety of tight situations.
Assured super tight installation, even in a 3-across situation (as long as the Foonf can be installed, it will be tight): Because the forward-facing Foonf uses Rigid LATCH and therefore plugs into the vehicle’s lower anchors, you’ll never need to worry that it’s installed too loosely. This is important in a 3-across situation where you must be certain that all three seats are independently tight, and they don’t just seem tight because they’re smack up against each other. The Foonf is the only forward-facing 5 point harness seat sold in the US to feature Rigid LATCH at this time.
Extremely narrow on the outside by still very comfy: The Foonf is narrow and streamlined on the outside but very roomy and comfy on the inside, even for bigger kids.
Longevity: The Foonf can be used forward-facing until about age 6.
Note: Great option for the side seats, NOT the center: Because the Foonf uses Rigid LATCH, it’s best placed on the side seats. It often fits nicely next to a rear-facing Clek Fllo in the middle seat. The Foonf is not a good choice for a forward-facing seat in the center because most vehicles do not have lower anchors in that position.
Other things we like, besides the narrow parts:
Extremely low profile, narrow width, and shallow sides make it a great option for tight center spots: The Radian’s design means it tucks in nicely next to other car seats, especially rear-facing seats. Often works well in the center with two rear-facing Foonfs on either side.
Easy to maneuver around and in/out: Kids have an easy time climbing in and out due to the Radian’s shape. It’s easier to get an infant carrier out of the center if the Radian is on the side (compared to a higher forward-facing seat.) Finally, it sits low to the vehicle seat so it’s less likely to obstruct a driver’s view out the rear window when its installed in the center.
Longevity: Most kids will fit until about age 6.
Note: Installation can often be tricky! In some vehicles you’ll need to use a locking clip and/or the double seat back recline trick.
Note: Not recommended for rear-facing: The Radian does not meet our criteria for a recommended narrow rear-facing convertible car seat because its rear-facing seat belt installation often does not yield a tight result and because when installed with LATCH, does not accommodate another car seat next to it.
Easy LATCH installation can be completed in under 3 minutes.
Easy to maneuver around and in/out: Kids have an easy time climbing in and out due to the Go’s shape, especially when the Go’s in the center. It’s easier to get an infant carrier out of the center if the Go is on the side (compared to a higher forward-facing seat.) The Go sits low to the vehicle seat so it’s less likely to obstruct a driver’s view out the rear window when its installed in the center. Finally, its lack of sides means an adult will be more comfortable sitting next to the Go than most other forward facing seats.
Longevity: Fits most kids until about age 6.
Extremely narrow on the outside but still super comfy: The Go is narrow on the outside but very roomy and comfy on the inside, especially for kids who like to sit criss-cross.
A forward-facing option for the center: Because its narrow and lacks sides, the Go works well installed with LATCH in the center (as long as the vehicle permits this) next to two rear-facing seats on the sides. Note that the seats next to it will likely need to be installed with the seat belt. Using the Go in the center may permit a family to install their infant seat on the side (instead of in the center, which is less convenient.)
Allows third row access in specific vehicles, when other car seats don’t: Great on vehicle seats that first fold forward and then slide forward for third row access. The IMMI Go can usually stay securely installed while the vehicle seat folds forward, unlike other forward-facing car seats.
Other things we like besides the narrow parts:
Note regarding installation: The Go does not want to be installed with the seat belt. It absolutely needs to be installed with the lower anchors and tether strap.
Great seat belt installation, especially on side seats: Nicely designed seat belt lockoff holds the seat belt tight and allows for an installation close to the door.
Longevity: Very high height capacity means this seat will last longer than others. Almost all children will fit in harness mode until about age 7. This is helpful in a tight three across situation where a booster would be hard to operate (because it is often very hard to buckle and unbuckle the booster’s seat belt in a tight 3-across. Using a harness instead of the booster removes this difficulty).
Other things we like (besides the narrow parts):
Note: We don’t recommend the Myfit in booster mode because the arm rests make buckling a challenge and because the shoulder belt tends to get stuck in the shoulder belt guide when a child leans forward. This is problematic because the seat belt is then too loose on the child.
Great seat belt installation in center or side seats: Fantastic seat belt tensioning device allows for an easier, tighter installation in most seating positions.
Accommodates protruding vehicle head restraints and rigid, angled seat belt buckles: The Exec’s design means it fits nicely even when vehicle features present a challenge. It’s very hard to find forward-facing seats that work with these vehicle features.
Longevity: Fits most kids until age 6.
Good visibility for the child using it: Because the Exec sits high off the vehicle seat, a child can easily see out the window. This is great until the child gets tall, when it can start to become a visibility issue for the driver if installed in the center position.
Other things we like (besides the narrow parts):
If you have a narrow spot where you need to fit a high back booster, you (sadly) don’t have many options. Having done hundreds of 3-across scenarios, we can say the Maxi Cosi Rodifix is the most likely high back booster to fit – and if the Rodifix doesn’t fit, there is literally NO other high back booster that will.
The most versatile high back option: To say we love the Rodifix would be an understatement. It’s the most versatile booster we’ve found (and we’ve tried them all).
Extremely narrow but still super comfy!!: Rodifix has the narrowest footprint and flexible sides, making it more likely to fit in narrow seating positions where other boosters won’t. At the same time it still accommodates wider kids fabulously due to its flexible sides and an absence of arm rests. If space is at a premium in your vehicle, then this is the seat to consider. If the Rodifix doesn’t fit, there is no other high back booster in the US will.
Thoughtful design to avoid misuse: This booster’s design has eliminated the most common (and most serious) misuse of all boosters: when someone accidentally puts the lap belt over one or both of the arm rests. Doing this puts the lap belt across the child’s belly, which is a dangerous misplacement that can cause severe injury or death in a crash. Because this booster doesn’t have arm rests, you can’t make this mistake when buckling up! The lack of arm rests also makes it easier for a child to see the buckle and to get their hand in to buckle and unbuckle themselves independently–something both kids and parents love.
Excellent head rest: The head rest is so well designed on the Rodifix that we’d love to use it ourselves! It captures the head perfectly so your kid’s head won’t be bobbing around during sleep. Keeping the head well positioned during sleep is an important part of keeping the whole body properly positioned in the seat belt – because if the head falls, sometimes the torso starts to fall forward or slump sideways, both of which are dangerous as the seat belt then won’t be on the proper part of the child’s body.
High back only. Does not turn into a backless booster.
Rigid back works with low vehicle headrests. The back of this booster is rigid enough to support the child’s head and does not need the vehicle seat back to come up to the child’s ears for whiplash protection. It also handles vehicle head rests that protrude better than most other boosters.
LATCH: Rodifix can be secured to the vehicle using rigid lower anchor connectors (rigid LATCH) although you likely won’t be able to use LATCH in a tight 3-across situation. Note that it is not required to secure this or any other booster to lower anchors.
Longevity: Most kids will fit in the Rodifix until somewhere between 8-10 years old, at which point they will likely move into a backless booster or pass the 5-Step Test.
Remember: In order to use a backless booster, you need to make sure the vehicle seat back comes up to at least the top of the child’s ears so it can provide adequate head support. If the vehicle seat back does NOT come up to at least the top of the child’s ears, then your child needs to use a high back booster in that seating position.
Narrowest option out of all available boosters: The RightGuide has the narrowest footprint out of all high back or backless boosters currently on the market in the US, making it a great option for narrow centers or for squeezing next to another car seat where other boosters wouldn’t fit.
Excellent design and fit to enhance safety: We like this booster for more than just it’s small size. We can say with no exaggeration that the RightGuide is the best thing we’ve ever seen in the category of backless boosters.The Rightguide fits both skinny and wider kids very well due to the lateral flexibility in the red belt guides. It has a slight upwards slant at the knees which enhances comfort and therefore safety, as it helps prevent kids from wanting to slouch (slouching puts the lap belt on the belly, which is dangerous!).
Extremely travel-friendly: The RightGuide is a fabulous choice for travel, playdates, and carpool. Weighing just 1.8 lbs and the size of a laptop, it easily slides into a child’s backpack and many purses, diaper bags, tote bags, etc. The red belt guides fold flush with the underside of the booster to make it super compact for carrying around when you aren’t in a car. We’ve traveled extensively both in the US and internationally with this booster, in a wide variety of vehicles, and have been very pleased with its convenience and performance.
IIHS: This booster has not yet been evaluated by IIHS… but in our informal testing of it with a variety of kids we have found that it offers a great belt fit for small and large kids in a variety of vehicles.
Vertical lap belt guides save space and add comfort: Turbo Go features completely vertical and very high lap belt guides, which make the seat more likely to fit in between others. These guides also better accommodate kids with bigger thighs. Because the guides sit higher than the child’s thighs and are not tapered, they don’t push into the child’s thighs the same way other booster belt guides do.
Comfort for bigger kids: Generous width and longer-than-average seat depth accommodate kids with longer legs. Note: the longer seat depth poses a potential problem for younger children as their knees may not bend naturally over the edge without slouching.
Travel friendly: This booster weighs 4 pounds and folds, so it fits nicely in a large backpack.
Lifts kids up: Turbo Go boosts the child up a fair amount (more so than the RightGuide) which is great for shorter kids. Note that this added height can be an issue for a taller kid if their head starts getting too close to the roof of the car or their head isn’t supported by the vehicle seat back or vehicle head restraint.
Narrow and lightweight: The Harmony Youth and Cosco Rise are both very lightweight and inexpensive narrow backless boosters. Due to differences in their contouring, one might fit better than the other in a specific narrow spot in your vehicle.
The Rise has a shallower seat depth than the Youth – so the Rise is better for shorter kids and won’t fit taller kids as well.
The Rise has not been evaluated by IIHS for its belt fit.
Chicco Keyfit30: Base often won’t install securely with the seat belt when pushed closer to the door
Peg Perego 4-35: Takes up a lot of space into the front seat, won’t tolerate being close to the door.
Baby Trend Flex-Loc: Lacks built in seat belt locking device on base so is often hard to securely install with the seat belt.
Cybex Aton2: Lacks longevity
Uppababy Mesa: Base won’t tolerate being close to door.
Diono Radian for Rear-Facing: Often won’t install securely with the seat belt, and has short usability (only 35 lbs) when installed rear-facing with LATCH.
Graco SlimFit: Lacks built-in seat belt locking device.
Cosco Scenera NEXT: Lacks built-in seat belt locking device and won’t typically install securely when positioned close to the door. Also has limited capacity due to its small size.
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FTC Disclosure: Affiliate links are included in this page. No monetary compensation was provided, however, a few of the reviewed products were supplied by the manufacturer or distributor to help facilitate the review. All opinions are those of The Car Seat Lady, LLC.