OTR vs MVTR: the two barriers your packaging has to get right

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What OTR and MVTR actually measure

Every flexible film is a filter, not a wall. Given enough time, oxygen and water vapor both migrate through it — the only question is how fast. OTR and MVTR are the two numbers that answer that question, and the whole point of OTR vs MVTR is that they answer it about two completely different molecules.

OTR is the oxygen transmission rate: how much oxygen gas crosses a given area of film in a given time. MVTR — moisture vapor transmission rate, also written WVTR (water vapor transmission rate) — is the same idea for water vapor. Lower is better in both cases: a low number means less of the molecule gets through, so the barrier is stronger. Here is the side-by-side.

Aspect	OTR (oxygen transmission rate)	MVTR / WVTR (moisture vapor transmission rate)
What crosses the film	Oxygen gas	Water vapor
Common unit	cc/m²/day (also cc/100 in²/day)	g/m²/day (also g/100 in²/day)
Standard test method	ASTM D3985 (coulometric sensor)	ASTM F1249 (infrared sensor)
Conditions that change the result	Temperature; humidity for some barriers	Temperature and a relative-humidity gradient
A lower number means	Better oxygen barrier	Better moisture barrier
It protects against	Oxidation, rancidity, color and flavor loss, aerobic spoilage	Moisture gain or loss, caking, sogginess, mold

The test-method names above come from ASTM International, which publishes the standard barrier tests film labs run. A supplier's quoted OTR or MVTR is almost always measured to one of these methods at a stated temperature and humidity — so those conditions are part of the number, not a footnote.

What OTR is: the oxygen barrier

Oxygen is the enemy of anything that oxidizes: fats and oils go rancid, pigments fade, vitamins degrade, roasted flavors flatten, and many microbes need oxygen to grow. If your product suffers from any of those, OTR is the number you care about most.

OTR is reported as a volume of oxygen (in cubic centimeters, "cc") passing through a square meter of film in one day — the everyday unit is cc/m²/day. A low-OTR film admits only a whisper of oxygen; a high-OTR film lets it pour through. Comparing two films only makes sense at the same measurement conditions.

A few practical notes on oxygen barrier that hold up generally:

• Thickness helps, but structure matters more. Adding a dedicated barrier layer (foil, metallization, or an EVOH core) usually does far more than simply making a poor-barrier film thicker.
• Barrier is only as good as its worst spot. A pinhole, a flex-crack, or a bad seal can undo an excellent OTR, which is why converting quality and seal integrity matter — see what causes delamination in flexible packaging.
• Oxygen already inside the pack still counts. Barrier stops new oxygen getting in; it does nothing about the oxygen sealed in with the product. That residual oxygen is what an oxygen absorber (scavenger) is for.

That last point is where the oxygen absorber calculator earns its keep: a high-barrier pouch keeps oxygen out, and a correctly sized scavenger mops up the oxygen that was already inside at seal time. The two work together, and getting only one right leaves the product exposed.

What MVTR is: the moisture barrier

MVTR — moisture vapor transmission rate — measures how much water vapor moves through the film, reported in grams of water per square meter per day, or g/m²/day. You will also see it called WVTR; the two terms are interchangeable. Again, lower is a stronger barrier.

Which direction the water travels depends on your product versus the outside air. A dry, crunchy, or hygroscopic product sitting in humid air gains moisture: crackers go soft, powders clump, effervescent tablets fizz prematurely, freeze-dried pieces lose their crunch. A moist product in dry air can lose moisture and dry out. Either way, the film's MVTR sets how fast that exchange happens.

One detail that trips people up: MVTR is always measured across a humidity gradient — a wet side and a dry side — so the test conditions (temperature and the relative-humidity split) are part of the number, and a figure quoted at one condition isn't comparable to one quoted at another. It's exactly the kind of spec a converter-ready sheet should pin down; our stand-up pouch spec guide walks through the fields that belong on one.

Why the two barriers are independent

This is the crux of OTR vs MVTR, and the part most people get wrong: the two barriers do not track together. A polymer that is excellent at stopping water vapor can be mediocre at stopping oxygen, and the reverse is just as common. Oxygen and water are different-sized molecules with different polarities, so a polymer's resistance to one tells you little about its resistance to the other.

Two classic examples make the point:

• EVOH is one of the best oxygen barriers in common use — but it is hygroscopic, so its oxygen barrier drops as it absorbs moisture. That is why EVOH is almost never used on the outside of a pack; it is buried as a core layer between moisture barriers that keep it dry.
• Polyethylene (PE), the sealant layer on most pouches, is a good moisture barrier but a poor oxygen barrier. On its own it keeps water out reasonably well and lets oxygen through freely.

Because no single common polymer is outstanding at both, high-barrier packaging is built as a laminate: a stack of layers where each one contributes a property — a moisture barrier here, an oxygen barrier there, a printable surface, a sealable inside. The cross-section of that stack is the real answer to "how do I block both?", and it is why understanding the layers matters more than chasing one hero material. Our overview of flexible packaging types covers how those laminates are assembled.

Barrier by material: a rough map

The table below is a directional guide, not a spec. Actual OTR and MVTR values depend heavily on grade, thickness, coating quality, and — for oxygen — humidity, so always confirm against the film supplier's published barrier chart and the ASTM test data behind it. Treat "High / Medium / Low" as typical relative behavior, not a guarantee.

Material / layer	Oxygen barrier	Moisture barrier	Note
Aluminum foil laminate	Very high	Very high	Close to a total barrier to both when intact; opaque; vulnerable to flex-cracking and pinholes
Metallized PET (metPET)	High	High	Foil-like barrier at lower cost and weight; barrier drops if the thin metal layer is scratched or creased
EVOH (co-extruded core)	Very high	Low–medium	Outstanding oxygen barrier but humidity-sensitive; must be buried between moisture-barrier layers
SiOx / AlOx-coated PET	High	High	Transparent high barrier for see-through packs; the coating is thin and can be damaged in converting
PVDC coating	High	High	Good dual barrier; less favored now on recyclability grounds
Nylon (PA)	Medium–high	Low	Good oxygen and aroma barrier plus toughness, but absorbs moisture
PET (plain)	Low–medium	Low–medium	Common print/structural layer; modest barrier on its own
BOPP / PP	Low	Medium–high	Decent moisture barrier, weak oxygen barrier
Polyethylene (PE)	Low	Medium–high	The usual sealant layer; good moisture barrier, poor oxygen barrier
Uncoated paper / kraft	None	None	No meaningful barrier alone; needs a liner or laminate to perform

Read down the two barrier columns and the independence jumps out: EVOH and nylon are strong on oxygen but weak on moisture, while PE and BOPP are the opposite. Only the foil, metallized, and coated structures are strong on both — which is exactly why they cost and weigh more. If recyclability matters, that trade-off sharpens, because the highest-barrier structures are typically the hardest to recycle; our guide to recyclable mono-material pouches covers how mono-material designs try to close that gap.

How to match the barrier to your product

The practical side of OTR vs MVTR is a buying decision, not a physics exam: know which molecule ruins your product, then buy the barrier that stops it. A simple sequence:

1. Name the failure mode. Does your product go rancid, fade, or stale (oxygen), get soft, clump, or dry out (moisture), or both? That answer picks OTR, MVTR, or both.
2. Set the barrier priority. Oxidation-sensitive products (coffee, nuts, oils, cured meat, many supplements) lead with a low OTR. Hygroscopic or crisp products (chips, crackers, powders, effervescents, freeze-dried) lead with a low MVTR. Plenty of products — jerky, trail mix, many snacks — need both.
3. Add light protection if needed. Light drives some oxidation reactions, so if UV or visible light is a factor, favor an opaque or metallized structure rather than clear film.
4. Handle the oxygen already inside. Even a perfect barrier can't remove the oxygen sealed in with the product. For sensitive foods, pair the barrier with an oxygen absorber sized to the headspace and product — size it with the oxygen absorber calculator.
5. Protect the barrier through production. A great OTR on paper means nothing if the film flex-cracks, the seal leaks, or the laminate delaminates. Confirm seal integrity and run a preflight check before you commit.

Coffee is the textbook OTR case: oxidation stales the roast, so coffee bags lead with a strong oxygen barrier and often a one-way degassing valve — see coffee packaging. Hard candy and many confections lean the other way, worrying first about moisture and bloom; our confectionery packaging guide covers that. Both sit within our broader packaging design guide, which ties barrier choices back to structure, artwork, and dieline.

How PackOS uses barrier data

Barrier is where structure meets material, and PackOS treats it that way. When you upload artwork or a spec, it detects the pack format and material construction, so the film stack behind your design — and the OTR vs MVTR trade-off it implies — is captured with the job rather than lost in an email thread. It travels into the quote and the proof. Watch the detection run on the design detection technology page, or see the whole platform on the technology overview. Once the structure and material are understood, pricing and production routing follow, because barrier drives both the substrate cost and the process.