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Oxygen absorber sizing comes down to a single multiplication. Air is about 20.9% oxygen by volume, so the oxygen a sealed pack contains is the air volume inside it multiplied by 0.209 — and an absorber is rated by how many cubic centimetres (cc) of oxygen it can take up, where 1 cc equals 1 mL. Size the sachet to that oxygen figure, add a safety margin of roughly 180–300%, and round up to the next standard size. Get the sealed volume right and the rest is arithmetic.
That is the whole method. A worked example: a pack that seals 500 mL of air holds 500 × 0.209 = 104.5 mL of oxygen. With a 200% margin that is a target of about 200 cc, so you would select a 200 cc absorber — or, on a tighter margin, a 150 cc or 100 cc unit.
An oxygen absorber's capacity is stated in cubic centimetres (cc, the same as mL) of oxygen — the volume of oxygen gas it can absorb, not its own weight in grams. That is why the rating maps directly onto the calculation above. A 30 cc absorber, for instance, is matched to roughly 150 cc of air, because 150 × 20% is 30 cc of oxygen. Read the rating as an oxygen volume, match it to the oxygen your pack contains, and the pack volume and the sachet size line up.
| Sealed air volume | Oxygen in that air (× 0.209) | Minimum absorber | Recommended with a 200% margin |
|---|---|---|---|
| 250 mL | ≈ 52 mL | 50 cc | 100–150 cc |
| 500 mL | ≈ 105 mL | 100 cc | 200–300 cc |
| 1,000 mL (1 L) | ≈ 209 mL | 200 cc | 400–600 cc |
| 2,000 mL (2 L) | ≈ 418 mL | 400 cc | 800–1,200 cc |
| 5,000 mL (5 L) | ≈ 1,045 mL | 1,000 cc | 2,000–3,000 cc |
The "minimum" column is the bare arithmetic; the recommended column is what you actually buy. Real packs leak, and hygroscopic or porous goods hold oxygen that comes out slowly, so the margin is not padding — it is the difference between a pack that holds and one that fails quietly.
Most commercial oxygen absorbers are iron-based: iron powder oxidises, consuming oxygen as it turns to iron oxide — in simplified form, 4 Fe + 3 O₂ → 2 Fe₂O₃. The reaction removes the oxygen from the sealed headspace and holds it as a solid, so the pack's internal oxygen falls to a level at which mould, aerobic bacteria and oxidative rancidity cannot proceed. Suppliers of food-grade absorbers commonly state that they pull the headspace down to 0.1% or less, and some to 0.01%, depending on the product and the film.
That target is why the pack has to be sealed, not just wrapped. An absorber can only hold oxygen down if new oxygen cannot keep leaking in, so it is used inside a low-permeability barrier bag and heat-sealed. Treated simply, the two rules are:
An oxygen absorber removes oxygen; a desiccant removes moisture. They sit in the same pack and solve different problems, which is why they are often used together rather than chosen between — the distinction is the whole subject of our deoxidizer vs desiccant page. Where moisture is the risk, the moisture side is handled by a medicinal and food desiccant sachet; the sizing method for the oxygen side is the calculation above. For the related question of how a whole sealed container is sized rather than a single pack, see how oxygen absorbers are sized for a container.
Give us the headspace volume and the product and we will match the sachet model and the barrier film. The absorbers themselves are on our deoxidizer (oxygen absorber) page, and how they combine with moisture control in regulated markets is covered in our food and pharmaceutical packaging compliance guide.
Written by the VEN Desiccant export team from the sizing rules our food and pharmaceutical customers apply and the ratings our suppliers publish. Drafting was AI-assisted; the arithmetic and the ratings were checked and edited by our team before publication. We publish it so a buyer can size an oxygen absorber from first principles instead of copying a number between packs. Treat the supplier's certificate of analysis and the film supplier's OTR figure for your actual goods as the controlling data.
Last checked: 11 October 2026.
Tell us the sealed headspace volume, the product and the film — we will match the sachet and the barrier bag.
