Last Updated on December 18, 2020
A first glance it seems perfectly reasonable for the TSA to ask people to pack carry-on toiletry liquids in a quart size bag when flying.
That is until you realize the geniuses at the TSA have unwittingly asked the general public to solve a so far unsolved math problem when determining the sizes of Ziplock bag they can use. We only want to bring liquids on planes not play at being Good Will Hunting!
You see, if you take a flat 2-dimensional Ziplock bag and put things inside it, it starts to take on a really complicated geometric shape that makes it incredibly difficult to accurately calculate the volume of the bag.
Thankfully we don’t really need to be accurate! Not even slightly accurate. The whole TSA quart bag rules are a bit of a mess really.
So How Big Is A Quart-Sized Bag?
The @AskTSA service on Twitter gets asked endless variations on this question!
- What is a quart size bag?
- What are the dimensions of a quart-sized bag?
- What size baggie for carry on liquids?
- What size bag for toiletries?
- What size of baggie for liquids & gels?
And they almost always copy and paste the same answer:
Here’s another example:
So the official TSA answer goes like this:
We don’t approve or endore any particular products. As long as the toiletry bag is the approximate dimensions of a quart-sized bag (6″ x 9″), you’ll be good to go through the checkpoint. Pls remove the toiletry bag from your carry-on & place it in a separate bin for X-ray screening at security.Transport Security Administration
So great, they have a cut and past answer, but it’s a bit lame.
There are lots of clear 1-quart bags that have other dimensions. And you don’t always happen to have a 6 x 9 plastic bag handy when you are packing your liquids for in your carry-on bag.
What about all the other sizes of ziplock bags? Are they 1 quart or under?
Don’t worry TravelingLight.com has you covered!
Flat Quart Size Bag Dimensions Calculator
This calculator that I created below doesn’t precisely calculate the volume capacity of a quart-sized toiletry bag, but it’s close enough.
It’s sort of hacked together to give you something you can use when you travel. It was created using the TSA’s assertion that a 6 x 9 inch Ziplock bag is quart sized to create the formula.
Go ahead and adjust the dimensions of the ziploc bag to find out if it's quart-sized and TSA approved.
You can see that there are numerous sizes of baggies that are 1-quart capacity.
The sandwich bag is a half-decent substitute when packing liquids in your hand luggage. It’s 6.5 x 5.8 inches and 0.7 quarts. So if you are using a sandwich bag you’ll have 70% of the maximum space of taking liquids on planes.
Here is the root of the problem in my opinion…
When the TSA says “quart-sized” they don’t really mean a bag that has a volume capacity of 1 quart or 946 ml.
Quart size technically means, a quarter of a gallon. But while it’s a liquids bag you are not filling it up with water from the tap. You’re filling it with bottles and containers. So you won’t fit a quarter of a gallon of toiletries in your quart bag. Check this post to see how many bottles you can actually fit when planning your packing list.
The TSA just want you to use a little plastic bag roughly the same size as those sold and marketed as a quart bags. They want it to be clear plastic so your items are easily inspected. They want to be able to see the 3.4 oz bottles or containers that you packed inside. That’s how the rules were initially set up (because of terrorists trying to take liquid explosives on to a plane in 2006) and I doubt much thought has been given to them since.
Surely, there must be a better system than unsustainable plastic bags in 2020 and it’s time the TSA revisited their guidelines to make this clearer.
Although it hardly seems worth worrying about the environmental impact of the plastic TSA liquids bag when you are about to fly in an airplane and dump vast amounts of co2 into the atmosphere.
Still, it is better to reuse your bag and in that case, you might want a toiletries bag that is a little more substantial.
The Myth of “TSA Approved” Quart Sized Bags
If you’re going to buy a clear toiletry bag that is more sturdy you’re going to want to make sure that it complies with the rules. It should be easy to find something right?
Erm… not in this crazy world.
The TSA approves of any clear quart size bag. But they don’t go around issuing a stamp of approval to manufacturers.
If they did many of the bags that claim to be “TSA approved” would fail miserably…
For not actually being quart-sized.
Often these bags have a gusset. While they might be smaller than 6 x 9 inches on the face they are over 1-quart volume because of the depth.
Let’s take this bag as an example. Currently, the top-selling TSA Approved Quart Sized bag on Amazon.
Because it’s a rectangle it’s relatively easy to estimate the volume of the bag.
7.2 * 5 * 2 = 72 cubic inches.
72 cubic inches is 1.25 quarts, so it’s 25 % too big to qualify as TSA approved!
It doesn’t stop them printing “quart-sized bag” on the product though.
Most of the bags that look like this are oversized and sometimes not only by a little.
And yet does it really matter? I guess that depends on how strict the TSA is about enforcing their liquids bag rule at the security checkpoint.
How Strict Are The TSA About Quart Sized Bags?
This is the part where you find out all your worrying was probably a waste of time.
At the end of the day, it comes down to the judgment of the TSA officer who inspects your toiletries bag.
And in general, they are not looking very closely at the capacity of your toiletries bag.
You only need to look at the reviews on Amazon to see that while it’s almost impossible to find a clear transparent “TSA compliant” quart bag that’s actually 1-quart size they all have happy customers regardless.
Almost everyone is getting away with it!
Occasionally someone like Kate does get into trouble:
If you do want to try to travel with a larger toiletries bag I recommend buying one that isn’t flat. It’s much less noticeable and the dimensions are unlikely to be checked if the front-facing dimensions of the bag are roughly 6 x 9.
You’d probably waltz through with a bag that was 6 x 9 x 2 inches which is almost 2 quarts!
The TSA security officers just eyeball it and so long as it’s about the shape of a paperback book it’ll pass.
There is no measuring or mathematical modeling involved!
How Many Quart Size Bags Can You Carry On a Plane?
You can only carry on 1 liquids bag per passenger in your hand luggage.
Do All Carry On Liquids Have To Be In A Quart Size Bag?
Pretty much yeah. All liquids must be stored in bottles or containers less than 100 ml or 3.4 oz. You can have 1 baggie. And it’s only 1 bag per person.
If you want to take liquids that are greater than 3.4 oz you need to pack them in checked luggage. The only exceptions to this rule are baby formula, breast milk, or juice for infants.
Can I Bring A Gallon Bag At The Airport?
A gallon bag is 4 quarts. You might have problems using such a large baggie, even if it’s only a quarter full of your liquid items.
Why should manufacturers care about correctly sizing their toiletries bags if the TSA doesn’t care?
They shouldn’t. They will sell more toiletry bags if they supply larger bags that can hold more liquids.
If a tiny percentage of passengers have a problem it won’t hurt their profits when 99% of travelers get away with it.
The “3-1-1 rule” isn’t really a rule… It’s a rule of thumb. The TSA officers aren’t standing around with measuring tapes to measure your liquids bag. It’s only enormous violations of the 3-1-1 rule that get noticed.
This makes sense because if the TSA suddenly started rigorously enforcing quart bag rules the lines at security would be massive!
It’s much less noticeable to use a bag with a gusset to increase size than a huge looking flat bag like a gallon ziploc.
So it depends on you…
Do you want to be 100% compliant? Or do you want to try to sneak through some extra liquids like so many other travel mavericks?
Incidentally, while you are worrying about the dimensions of your quart size bag roughly 10 people turn up at the security check-point every day in the US with a loaded firearm. Go figure!
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