Oxygen absorber calculator
Oxygen is what stales dry food. Tell us the container and how many you're packing, and this sizes the absorber you need, and the simplest way to buy it.
Sized at 500cc per gallon: the safe end of the 300–500cc guideline, which allows for the air trapped between food particles. Absorbers are cheap and excess is harmless, so rounding up never hurts.
Any combination that meets the total works. Use them fast once the pack is opened, they start absorbing the moment they hit air.
How much do you actually need?
The working guideline across the food-storage world is 300–500cc of oxygen absorber per gallon of dry food. The spread exists because it depends on how much air is trapped between the food: dense, small particles like sugar or salt leave little air and need less, while airy foods like pasta or dehydrated vegetables trap more and need more. Sizing at the top of the range (500cc per gallon) covers you for either, and because absorbers are cheap and any excess is simply left unused, rounding up never causes a problem.
Why oxygen, not moisture
Oxygen absorbers and desiccants do different jobs. Absorbers pull the oxygen that lets fats go rancid and pantry pests survive; desiccants pull moisture. For long-term storage of already-dry staples, oxygen is the enemy, which is why absorbers, not desiccants, are what take rice and beans from a year to decades. Both live in our oxygen absorbers & desiccants rankings.
Using them without wasting them
Absorbers start working the moment they meet air, so open the pack only when you're ready to fill bags, and reseal the spares immediately in an airtight jar (a vacuum-sealed jar is ideal). Pair them with the right mylar bags and a food-grade bucket and the dry-storage system is complete.
Sources
- Oxygen absorber technical reference. Covers cc-per-gallon sizing and the 0.1% O₂ target.
- Oxygen absorber size chart. Per-container recommendations, including 2,000–2,500cc for 5-gallon buckets.