Oxygen Absorber Calculator for Mylar Bags, Jars & Buckets
Find how many cc of oxygen absorber each container needs and which of your packets to use.
Counts the whole container as air. Best for freeze-dried food, which is light and full of air pockets.
Advanced settings (safety margin)
Oxygen Absorber Needs
1 × 1000 cc per container
Air is about 21 % oxygen. Absorbers pull oxygen out to protect food from spoilage, bugs and mold.
Estimates for planning, not food-safety advice. Freeze-drying does not kill bacteria — follow tested food-safety guidance.
Air is about 21 % oxygen, so the absorber must handle 0.21 × the air left in the container. A 1-gallon container (3,785 mL) holds up to about 795 cc of oxygen if you count the whole volume as air — the safe assumption for light, porous freeze-dried food. For dense foods like rice, Sorbent Systems subtracts the product's weight; its 5-gallon bucket of 35 lb of rice needs about 644 cc, so a 750 cc absorber.
How to use
- Choose the container or enter its volume.
- Choose the mode.
- Tick the packet sizes you have.
- Read how many packets go in each container.
Worked example
1-gallon mylar, conservative: 3,785 mL × 0.21 = 795 cc → with 100/300/500/1000/2000 cc packets on hand, use 1 × 1000 cc. With only 100/300/500 cc packets: 1 × 500 + 1 × 300 cc.
How it's calculated
residual air × 0.21 (oxygen share of air) × (1 + safety margin), then the smallest number of your packets whose total is at least that.
Frequently Asked Questions (FAQ)
How many oxygen absorbers for a 5-gallon bucket?
Count the bucket's real volume and your mode. Sorbent Systems' worked example (18,942 mL bucket, 35 lb rice) needs about 644 cc of oxygen absorption → 750 cc. Light freeze-dried food leaves much more air, so the conservative mode asks for more.
Is it OK to use more than needed?
Extra capacity is not a problem for the food; too little leaves oxygen behind. This calculator never rounds down.
Why does the mylar bag hold less than its size?
Sealing and folding reduce the usable volume; the presets use the nominal size, so the result errs on the safe side.
Sources
- UC Master Food Preserver presentation 'Freeze Dryer' (Aug 2025)
Poor freeze-drying candidate foods, long-term storage requirements (oxygen, light, moisture)
- Sorbent Systems — Oxygen Absorbers: Measuring Volume of Oxygen
Residual air × 0.21 method and 5-gallon bucket rice worked example
Last reviewed: 2026-10-26
Built and maintained by Numberwright. Water contents come from the USDA nutrient database; every formula and source is listed on this page. Found a mistake? Contact details coming soon.
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