How to size an oxygen absorber
An oxygen absorber protects dry goods by pulling the oxygen out of the sealed air around them — stopping oxidation, rancidity, mold, and pantry pests. The right size depends on one thing the static charts online never actually compute: how much air is trapped in your package after the product goes in. This calculator does that math.
The steps: measure the internal volume, add the empty headspace to the air trapped between the pieces of product to get the residual air, take about a fifth of that (air is 20.9% oxygen) to get the oxygen to remove, then pick an absorber rated at or above it. Rounding up to the next standard size builds in margin, and extra capacity is harmless. As a floor for dry foods, USU Extension recommends 300 cc for a one-gallon container or #10 can and three 500 cc packets for a 5-gallon container.
Common absorber sizes by bag
These are typical starting points for full mylar bags of dense dry goods; use the calculator above for your actual fill.
| Bag / container | Typical residual air | Common absorber |
|---|---|---|
| Quart mylar (dense grain) | low | 100–300 cc |
| 1-gallon mylar (dense) | moderate | 300–500 cc |
| 1-gallon mylar (light/fluffy) | high | 500–1000 cc |
| 5-gallon bucket liner | very high | 1500–2000 cc |
Rules of thumb are a starting point, not a spec — a bag of whole beans traps far less air than the same bag of puffed snacks. Compute yours above, and remember the absorber only works inside a truly airtight, high-barrier bag.
Questions
What size oxygen absorber do I need?
Size it to the oxygen in the residual air of the sealed package: the empty headspace plus the air trapped between the pieces of product, which is roughly 40% of a full bag of grains or beans and more for pasta or freeze-dried food. Oxygen is about 20.9% of that air, so round up to a standard absorber rated at least that high. For dry foods, USU Extension recommends at least 300 cc per gallon of container. The calculator above works it out from your dimensions, fill level and food type.
Are oxygen absorbers rated by oxygen or by air?
They are rated by the cubic centimeters of oxygen they can absorb, not air. Because air is only about one-fifth oxygen, a 100 cc absorber can handle roughly 475 cc of air. Some charts size to the full air volume instead, which over-provides several times over; this tool sizes to the oxygen, rounds up to a standard size and shows the residual air beside it.
Can I use multiple oxygen absorbers together?
Yes. Absorber capacity adds up, so two 500 cc absorbers equal one 1000 cc. Using several smaller absorbers is a common and reliable way to hit a large rating, and slightly over-provisioning does no harm. When a container needs more than a 2,000 cc packet, the calculator recommends a number of packets instead of one size.
Do oxygen absorbers work in any bag?
No. They only work inside a genuinely airtight, high-barrier package such as a foil or metallized mylar bag with an intact heat seal. In a permeable bag, or one with a channel leak in the seal, oxygen keeps entering and the absorber is quickly exhausted. Always verify the seal.
Does the calculator give me a price?
No, it sizes the absorber, not the cost. It computes residual air, oxygen to remove, and the recommended cc rating from your container dimensions, fill level and food type, then rounds up to a standard absorber size.
Labeling the bags?
PackOS Quick Quote prices custom roll labels today — if your mylar bags or pouches need a label, upload the artwork for an instant label quote. Mylar and stand-up pouch quoting is coming soon.