Guides
Cargo Box vs Cargo Bag
The bag wins on cost, storage and needing no rack. The box wins on everything you notice while driving.
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Buy a cargo bag if you have no roof rack, no storage space or no appetite for spending box money — it is the only rooftop option that works on a bare roof and folds into a cupboard afterwards. Buy a hard cargo box if you travel often, carry anything valuable, or care about noise and fuel, because the shell is better at all three.
The decision usually comes down to one question nobody asks first: do you already have crossbars? If you do, a box is a far smaller purchase than it appears and the comparison tilts its way. If you do not, a bag with door-hook straps avoids the entire cost of a rack system, and that gap is larger than the difference between the bag and the box.
Below: the side-by-side, the three things people get wrong about bags, then the bag and the box we would actually buy.
Quick picks
Tap any row to jump to the full write-up below. Scores are our editorial judgment on published specifications — not a star rating, and not a product we claim to have tested.
| # | Product | Best for | Score | Price |
|---|---|---|---|---|
| 1 |  RoofPax Car Roof BagWaterproof construction with door-hook straps included, so it mounts to crossbars or to a completely bare roof. | Best bag, and best with no rack | 7.8 | |
| 2 |  Thule OutboundThule's soft bag, built to mount to crossbars rather than a bare roof — a tidier, better-secured install than door hooks. | Best bag if you have crossbars | 7.7 | |
| 3 |  Thule Force 3Roughly 300 to 610 liters, sealed, locking and dual-side opening — everything the bag gives up, for several times the price. | The box side of the comparison | 8.3 |
Prices checked October 11, 2026. Product photographs come from Amazon where the listing is matched, and are representative stock images otherwise. Affiliate disclosure.
#1 · Best bag, and best with no rack
RoofPax Car Roof Bag
Waterproof construction with door-hook straps included, so it mounts to crossbars or to a completely bare roof.
- Type
- Soft waterproof bag
- Mounting
- Crossbars or door-hook straps
- Rack needed
- No
- Storage
- Folds away
What works
- The only option here that works on a bare roof
- Folds into a cupboard between trips
- Waterproof rather than water-resistant
- A fraction of the cost of a shell plus bars
What doesn’t
- No security at all
- Door-hook straps can track water into door seals in heavy rain
- Noisier than a shell when packed full
Our scoring
7.8overall
#2 · Best bag if you have crossbars
Thule Outbound
Thule's soft bag, built to mount to crossbars rather than a bare roof — a tidier, better-secured install than door hooks.
- Type
- Soft cargo bag
- Mounting
- Crossbars
- Rack needed
- Yes
- Build
- Branded hardware and webbing
What works
- Mounts to bars, so no straps run through the door frames
- Better webbing and buckles than the generic bags
- Still folds away for storage
What doesn’t
- Requires crossbars, unlike a door-hook bag
- Costs more than a generic bag for the same volume
- Still fabric: no security, more noise than a shell
Our scoring
7.7overall
#3 · The box side of the comparison
Thule Force 3
Roughly 300 to 610 liters, sealed, locking and dual-side opening — everything the bag gives up, for several times the price.
- Sizes
- Roughly 300 to 610 liters
- Shell
- Hard
- Security
- Locking
- Opening
- Dual side
What works
- Locks, which no bag does
- Quieter and more aerodynamic than a packed bag
- Keeps rain, spray and road salt off everything inside
- Holds its shape, so packing is predictable
What doesn’t
- Several times the cost of a bag, plus bars if you lack them
- Needs real storage space all year
- Cannot be used on a bare roof at all
Our scoring
8.3overall
Side by side
| Property | Cargo bag | Hard box |
|---|---|---|
| Works on a bare roof | Yes, with door-hook straps | No — crossbars required |
| Cost | A fraction of a box | Box plus bars plus fit kit |
| Storage at home | Folds into a cupboard | Needs a wall or a hoist |
| Security | None | Locks, contents hidden |
| Noise and drag | Worse, and worse when overfilled | Shaped to reduce both |
| Weather | Waterproof fabric, seams and zips are the weak point | Sealed shell |
Three things people get wrong about bags
- Overfilling. A stuffed bag is a bluff, round shape in clean air — the worst possible aerodynamics and the loudest configuration. Pack it full but flat, and strap over the top so the profile stays low.
- Door-hook straps and water. Straps that run through the door frames break the seal line. In sustained heavy rain water will track along the webbing into the cabin. On a long wet trip, bars and a bar-mounted bag are the better answer.
- Treating a bag as secure. It is fabric and a zip. Nothing you would mind losing should travel in one, and nothing should be left in it at a hotel.
None of these are reasons not to buy a bag. They are the things to know before you do, and all three are manageable.
Noise and fuel, which is where the box earns its money
A hard shell is shaped by a wind tunnel; a bag is shaped by what you put in it. That difference shows up as noise at 65 mph and as fuel over a long day.
Consumer Reports’ measurements of rack-and-carrier fuel penalties apply to both, and we quote them in the gas mileage guide. A well-packed low bag is not dramatically worse than a tall box; an overfilled bag is worse than anything.
Noise has a simpler fix than fuel: keep the load low and flat, make sure no strap tail is loose, and check the bars themselves. Hollow bars with open channels drone regardless of what is on them — the wind noise guide covers which fixes work.
How to decide
- No rack and one trip a year: bag with door hooks, without hesitation.
- No rack and several trips a year: price bars plus a bar-mounted bag against bars plus a box. The bars are the expensive part either way.
- Rack already fitted: the box is a smaller step than it looks, and it is the better product.
- No garage: bag. A hard box with nowhere to live becomes a hard box in the hallway.
- Skis, or anything valuable: box. See cargo boxes for skis.
Still weighing the whole idea? The broader arithmetic is in are cargo boxes worth it.
Common questions
Is a cargo bag as good as a cargo box?
Can you use a cargo bag without a roof rack?
Are rooftop cargo bags waterproof?
Is a cargo bag noisier than a box?
Sources
Not sure it fits your car?
Our vehicle pages carry the published roof load limit, the roof type by model year, and what actually mounts to it — cited, and honest about what the manufacturer does not publish.
Read next
The Best Rooftop Cargo Bags
Soft roof bags with and without a rack, what they cost you, and the vehicles that should not use one.
Roof Rack vs Cargo Box
Why a box needs a rack, what the full setup costs, and when a basket or bag beats both.
Are Cargo Boxes Worth It?
The honest arithmetic on a roof box: trips per year, fuel penalty, storage and the alternatives.
The Best Cargo Boxes for Sedans
Cargo boxes that suit a sedan's short bar spread and lower roof limit, not an SUV's.