OTR vs WVTR: Which Matters for Your Packaging?

When someone hands you a flexible packaging specification, two numbers tend to show up quickly:

OTR and WVTR.

Both describe how well a packaging material slows something from passing through it. But they measure two completely different threats to the product.

And depending on what you're packaging, one may matter significantly more than the other.

The mistake is assuming that a film described as "high barrier" automatically provides the protection your product actually needs.

It may not.

What Is OTR?

OTR stands for Oxygen Transmission Rate.

It measures the rate at which oxygen passes through a packaging material under specified test conditions.

In general:

Lower OTR = greater resistance to oxygen transmission.

That matters for products that can be damaged by oxidation.

Examples include:

• coffee
• nuts
• products containing fats or oils
• certain vitamins and supplements
• nutraceutical powders
• flavor-sensitive products
• products susceptible to color changes
• ingredients that lose potency through oxygen exposure

Oxygen entering a package can contribute to rancidity, flavor changes, color degradation, and changes in certain sensitive ingredients.

That makes OTR an important part of the specification for many food and nutraceutical applications.

But it isn't the whole specification.

What Is WVTR?

WVTR stands for Water Vapor Transmission Rate.

It measures the rate at which water vapor passes through a packaging material under specified conditions.

In general:

Lower WVTR = greater resistance to moisture transmission.

That becomes particularly important for products that absorb moisture from the environment or need to retain a specific moisture level.

Examples include:

• drink powders
• electrolyte mixes
• protein powder
• collagen
• powdered supplements
• hygroscopic ingredients
• crackers and crunchy snacks
• gummies
• certain pet products
• dry food ingredients

Moisture entering the package can cause powders to clump, reduce flowability, soften crispy products, alter texture, or otherwise change how the product performs.

For those applications, a film can have excellent oxygen protection and still fail because its moisture barrier isn't sufficient.

OTR vs WVTR: They're Not Interchangeable

This is the most important distinction.

A material that performs well against oxygen does not necessarily perform equally well against water vapor.

And the reverse is also true.

Think of them as two separate specifications:

That means the correct question isn't:

"Is this a high-barrier film?"

It's:

"High barrier against what?"

Why Test Conditions Matter

OTR and WVTR values shouldn't be compared without looking at the test conditions.

Temperature and humidity affect transmission behavior, and the reported result only makes sense when you know the conditions under which the material was tested.

For example, two film suppliers may provide different OTR values for what appears to be a similar structure.

If those measurements were taken under different temperature or humidity conditions, comparing the numbers directly can be misleading.

When evaluating specifications, look for:

• test method
• temperature
• relative humidity
• material gauge
• whether the data is for raw film or a finished laminate
• whether the result reflects a finished package or only the web material

ASTM D3985 is one standardized method used to measure oxygen transmission through plastic films and laminates.

ASTM F1249 is commonly used for measuring water vapor transmission through flexible barrier materials.

The important point for a packaging buyer isn't memorizing the test methods.

It's making sure you're comparing equivalent data.

Which Matters More for Powders?

For many dry powders, WVTR can be the first problem to solve.

A moisture-sensitive powder may:

• clump
• cake
• lose flowability
• become difficult to dispense
• stick inside the package
• change texture or appearance

Products such as hydration powders, protein powders, collagen, greens, powdered supplements, and certain food ingredients can all be affected.

But oxygen may still matter.

If the formula includes oxygen-sensitive ingredients, flavors, oils, vitamins, or other actives, then OTR also becomes part of the specification.

So a powder package may need excellent moisture protection and meaningful oxygen protection.

That's why the product formulation has to drive the structure.

Which Matters More for Coffee?

Coffee is heavily affected by oxygen.

Once roasted, exposure to oxygen contributes to staling and loss of desirable flavor and aroma.

That makes low OTR important.

But coffee packaging also has to address:

• moisture
• aroma retention
• light exposure
• carbon dioxide released after roasting
• degassing valve requirements

So even here, choosing packaging based on one number alone misses much of the system.

The barrier structure, pouch construction, seals, and valve all have to work together.

Which Matters More for Snacks?

For a crunchy snack, moisture can be the obvious enemy.

If enough water vapor enters the package, texture suffers.

But products containing fats or oils can also oxidize, making OTR relevant to flavor stability and rancidity.

That is why snack structures often balance:

• moisture barrier
• oxygen barrier
• aroma protection
• seal integrity
• puncture resistance
• line performance

Again, there isn't one universal "snack film."

Which Matters More for Gummies?

Gummies are especially interesting because moisture movement can occur in either direction.

Depending on the formulation and storage environment, the product can gain or lose moisture.

That can affect:

• softness
• hardness
• stickiness
• appearance
• texture

Some formulations or active ingredients may also require oxygen or light protection.

The correct structure depends on the actual product—not simply the fact that it is a gummy.

OTR and WVTR Aren't the Same as Shelf Life

A low OTR or WVTR does not automatically guarantee a particular shelf life.

Film performance is only part of the finished package.

Actual product protection also depends on factors such as:

• package dimensions
• exposed film area
• headspace
• seal integrity
• zipper or closure
• degassing valves
• pinholes
• flex cracking
• filling conditions
• residual oxygen
• storage temperature
• humidity
• distribution conditions
• product formulation

A technically excellent film can still produce a poor package if the seals aren't reliable.

Likewise, an unnecessarily aggressive barrier structure may add cost without materially improving the finished product.

The objective is not to chase the lowest possible number.

The objective is to determine the barrier performance the application actually needs.

Film Structure Matters

OTR and WVTR are typically achieved through a combination of layers rather than one material doing everything.

A flexible structure might include:

Outer layer

Provides:

• printability
• stiffness
• heat resistance
• abrasion resistance

Barrier layer

Provides some combination of:

• oxygen barrier
• moisture barrier
• light protection
• aroma retention

Sealant layer

Provides:

• package closure
• hot tack
• seal strength
• product compatibility
• compatibility with the filling equipment

Materials such as PET, PE, nylon, EVOH, metallized films, foil, and coatings can all play different roles.

The structure has to work as a system.

A good barrier film still has to print, form, fill, seal, ship, and open correctly.

Don't Automatically Specify the Highest Barrier

It's tempting to assume that more protection is always safer.

Commercially, that's not always the right answer.

Increasing barrier can mean:

• more expensive materials
• additional layers
• metallization
• foil
• more complex laminations
• different sealing characteristics
• greater stiffness
• additional converting requirements
• fewer recyclability options

If a less complex structure achieves the required product performance, moving to a substantially higher barrier may only add unnecessary cost.

That's why good specification work starts with the required outcome.

How to Determine the Right OTR and WVTR

Instead of starting with a film, start with the application.

1. Understand the product

Determine what actually causes degradation.

Is it sensitive to:

• oxygen?
• moisture?
• light?
• aroma migration?
• grease?
• temperature?

2. Define the shelf-life target

A package intended to protect a product for six months may require a different structure than one expected to remain stable for 18 or 24 months.

3. Consider storage and distribution

A package sitting in climate-controlled storage faces a different environment than one exposed to heat and humidity through distribution.

4. Understand the packaging format

Rollstock, stand-up pouches, sachets, stick packs, and other formats create different package geometries and sealing requirements.

5. Understand the filling equipment

The structure still has to run.

That includes:

• stiffness
• coefficient of friction
• web tracking
• seal initiation temperature
• hot tack
• dwell time
• line speed

6. Establish performance targets

Once the risks are understood, OTR and WVTR targets can become part of the package specification.

7. Validate the finished package

Where shelf life is critical, evaluate the finished package and the actual product rather than relying solely on the raw-film specification.

What Should You Ask Your Packaging Supplier?

If you're comparing structures, ask for more than a material name.

Request:

• OTR
• WVTR
• testing conditions
• test method
• total film gauge
• complete film structure
• recommended application
• sealant information
• forming and filling compatibility
• available samples
• validation or trial recommendations

And give your supplier enough information to make a useful recommendation.

At minimum, provide:

• what the product is
• product form
• target fill weight
• desired shelf life
• package format
• filling equipment
• expected volumes
• known moisture sensitivity
• known oxygen sensitivity
• current package structure, if available

OTR vs WVTR: The Short Answer

If oxygen damages your product, OTR matters.

If moisture damages your product, WVTR matters.

If both can damage it, both matter.

And in many real packaging applications, the answer is exactly that: both numbers matter, but not necessarily equally.

The job is to determine which threat is driving the package requirement and build the film structure around that application.

Need Help Determining Your Barrier Requirements?

You don't need to know the exact OTR, WVTR, or laminate structure before starting a packaging conversation.

Tell us:

• what you're packaging
• how long it needs to last
• what environmental conditions it will see
• how it will be filled
• what format you're considering

Western Packaging can help work backward from those requirements to an appropriate flexible packaging structure.

Learn more about barrier films for flexible packaging, or talk with our team about your application.