Figuring out which packet to throw into your Mylar bags usually starts with looking at an oxygen absorber size chart to make sure you aren't under-doing it. If you've ever stood over a pile of bulk rice and a stack of shiny bags wondering if one little packet is enough, you aren't alone. It feels like a bit of a guessing game at first, but once you get the hang of how these little guys work, it's actually pretty straightforward.
The whole goal of using these absorbers is to strip the oxygen out of your storage containers so your food doesn't go rancid, grow mold, or get infested by bugs. But since oxygen only makes up about 21% of the air around us, you don't need to absorb everything in the bag—just that specific 21%. That's where the "cc" (cubic centimeter) ratings come into play.
Why the Size of the Packet Actually Matters
If you use a packet that's too small for the container you're using, you'll leave behind enough oxygen for spoilage to happen. It might take longer than it would without any absorber at all, but you're still not getting that 25-year shelf life people talk about. On the flip side, you can't really "over-absorb." If you put a massive 2000cc absorber into a tiny pint jar, the only thing you're hurting is your wallet because those big ones cost more.
An oxygen absorber size chart helps you find that "Goldilocks" zone. Most people tend to overshoot just a little bit to be safe, which is honestly a smart move. It's better to have extra absorption capacity than to realize five years from now that your wheat berries have gone stale because you tried to save a few cents on a smaller packet.
Understanding the "CC" Ratings
When you look at a chart, you'll see everything measured in CCs. This stands for cubic centimeters, and it refers to the amount of oxygen—specifically oxygen, not total air—that the packet can handle.
For instance, a 100cc packet is designed to pull 100ml of pure oxygen out of the environment. Since air is only about one-fifth oxygen, that 100cc packet is actually dealing with about 500ml of total air volume. This can get confusing if you try to do the math in your head while you're busy packing bags, which is why having a reference chart is a lifesaver.
Common Sizes You'll Encounter
- 50cc to 100cc: These are the little ones. You'll usually use these for small glass jars, pint-sized Mylar bags, or if you're canning spices and seeds.
- 300cc to 500cc: This is the most popular range. A 300cc packet is usually the standard for a 1-quart jar or a small Mylar bag (about 7x10 inches). 500cc gives you a nice buffer for 1-gallon bags if the food is dense.
- 2000cc to 2500cc: These are the "big daddy" packets. You use these for 5-gallon buckets. If you're sealing up a large bucket of beans or grain, you'll want at least 2000cc to make sure the job gets done.
The Secret Variable: Void Space
Here's where things get a little tricky. Not every one-gallon bag is the same. If you fill a bag with white rice, the grains are small and packed tightly together. There isn't much air left in the bag—this is called low "void space."
But if you fill that same bag with chunky pasta like rotini or large elbow macaroni, there's a ton of air trapped in the gaps between the noodles. Even though the bag size is the same, the pasta bag has way more oxygen inside it than the rice bag.
This is why a good oxygen absorber size chart will often give you a range. For dense foods (powder, flour, rice), you can go with the lower end of the CC recommendation. For "airy" or loose foods (pasta, cereal, freeze-dried snacks), you should always jump up to the next size or even double up on packets.
A Quick Cheat Sheet for Mylar Bags and Jars
If you just want the quick answers without doing the math, here is a general breakdown of what most people use in the real world:
- Small Pouch (Pint size): 100cc is plenty.
- Quart Jar / Small Mylar Bag: 300cc is the sweet spot. It's a bit of overkill for a quart, but it ensures a total scrub of the oxygen.
- 1-Gallon Mylar Bag: 300cc works if it's packed tight with something like flour, but 500cc is much safer for general use.
- 2-Gallon Mylar Bag: Go with 600cc to 1000cc depending on how "holey" the food is.
- 5-Gallon Bucket/Bag: 2000cc is the industry standard. Some people even use 2500cc just to be absolutely certain, especially with things like pasta.
Why Your Bag Might Not Look Like a Vacuum Seal
One of the biggest frustrations for people new to food storage is when the bag doesn't "suck in" like a vacuum-sealed package. They look at their oxygen absorber size chart, they put the right packet in, they seal the bag, and two days later it still looks like there's air in there.
Don't panic! Remember, the absorber only removes the oxygen (21%). The other 79% of the air is mostly nitrogen, which the absorber doesn't touch. If you have a bag with a lot of "headspace" (empty air at the top), the bag might not look tight even if the oxygen is completely gone. As long as your seal is good and the absorber was fresh, your food is protected.
The "vacuum look" is more common with thin Mylar bags or when you've squeezed out almost all the air before sealing. With heavy-duty 7-mil bags, the material is sometimes too stiff to show that "shrink-wrapped" effect anyway.
Handling Your Absorbers So They Don't Die
You could have the most accurate oxygen absorber size chart in the world, but it won't matter if your packets lose their oomph before they even get into the bag. These things start working the second they hit the open air.
If you open a pack of 50 absorbers and leave them sitting on the counter while you slowly fill your bags, they'll be "spent" before you even zip the last bag shut. You'll notice them getting warm—that's the chemical reaction happening.
Pro tip: Only take out what you need for the next 10 or 15 minutes. Put the rest in a small glass mason jar and screw the lid on tight. This stops the reaction and keeps them fresh for the next batch. If the packets feel hard or crunchy, they're likely already used up and won't do you any good. They should feel soft and powdery, like they're filled with fine sand.
Can You Use Too Many?
I get asked this a lot: "Can I just throw two 500cc packets in a gallon bag?"
Absolutely. There is zero downside to using more than you need, other than the fact that you're spending a few extra cents. In fact, if you're sealing up something expensive like freeze-dried meat or a long-term supply of coffee, it's a great insurance policy. If one packet happens to have a manufacturing defect (which is rare but possible), the second one has your back.
Just don't go the other way. Trying to "stretch" a 300cc packet into a 2-gallon bag is a recipe for wasted food and wasted money.
Trusting the Process
Long-term food storage can feel a bit like a science experiment, but it's one that has been perfected over decades. By sticking to a reliable oxygen absorber size chart, you're taking the guesswork out of the equation. Just remember to account for the type of food you're storing, keep your packets sealed until the last possible second, and ensure your heat seal is wide and strong.
Once those bags are tucked away in a cool, dark place, you can rest easy knowing that the little iron-filled packet is doing exactly what it was designed to do: keeping your food fresh for the long haul. It's a small investment for a lot of peace of mind.